Temperature overshoot and tipping points

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Key points:

  • Under the Paris Agreement, countries committed to limiting global temperature increase to 1.5°C or ‘well below’ 2°C above pre-industrial levels. However, even in an optimistic emissions scenario, the chance of limiting warming to 1.5°C by the end of the century is now virtually zero.
  • Our journey to achieving Paris Agreement goals will likely entail ‘temperature overshoot’, where warming exceeds a specified level (typically 1.5°C to 2°C) for 10 years or more before returning to that level in the future. 
  • Ninety percent of the mitigation pathways in the IPCC’s Global Warming of 1.5°C report that limit warming to 1.5°C by 2100 include temperature overshoot.
  • Pathways that limit warming to 1.5°C with limited or no overshoot require deep, rapid, and sustained reductions in emissions, as well as some carbon dioxide removal to compensate for sectors that cannot be decarbonised.
  • Even temporary overshoot increases the risk of Earth systems reaching ‘climate tipping points’, catalysing large and often irreversible changes. For example, deforestation in the Amazon could trigger a deforestation-drought feedback loop, rapidly transforming the region into a savanna.
  • Every increment of avoided warming can make a difference. Keeping overshoot as short and at as low a temperature as possible is critical to avoid sudden, cascading and irreversible climate impacts.
  • Without rapid emissions cuts now, we will need to rely more heavily on large-scale carbon dioxide removal to bring temperatures back down after overshoot, which comes with risks and uncertainties. 
  • Other proposed large-scale climate interventions, known as geoengineering, fail to address the root causes of climate change and introduce additional severe risks. 
  • Strategically targeting ‘positive socio-economic tipping points’ – which are conditions that accelerate the deployment of technologies or practices to reach net zero – could help drive decarbonisation and allow us to meet the 1.5°C target.

Surpassing the Paris Agreement limits

Last year, the Earth’s average temperature reached around 1.5°C warmer than pre-industrial times. The average warming for the decade between 2015 and 2024 was 1.24°C above pre-industrial times. The heating is predominantly a result of human activities1Human-cased warming is estimated to have caused 1.36°C of warming in 2024, relative to 1850–1900., primarily the burning of fossil fuels. This warming has had widespread adverse impacts on people and nature, which will worsen as the climate continues to warm. 

The Paris Agreement was adopted at COP21 in 2015 by most countries worldwide – countries that are collectively responsible for 98% of human-caused emissions – with the primary goal of avoiding the most devastating impacts of climate change. The agreement aimed to limit “the increase in the global average temperature to well below 2°C above pre-industrial levels” and to pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels” by the end of the century. The US, currently responsible for 13% of global emissions, announced its withdrawal from the Agreement in January 2025.

It is now clear that achieving the Paris Agreement goals will mean stricter measures to reduce emissions. Net carbon dioxide emissions will need to fall by 48% by 2030 to keep warming to 1.5°C, according to the latest IPCC assessment, published in 2022. More recent estimates suggest emissions would need to fall >around 50% over the same timeline. The 2024 Emissions Gap Report finds that, even under an optimistic scenario where all NDCs and net zero pledges are met, the chance of limiting warming to 1.5°C by the end of the century is “virtually zero”. The 2023 Emissions Gap Report gave a 14% chance, as, at the time, there were more opportunities to scale down emissions. 

Countries had agreed to submit more ambitious national climate plans by 2025 as part of the Paris Agreement. However, as of October 2025, countries have only pledged to reduce their emissions by 1.6 billion tonnes more than in their previous NDCs, leaving a gap of 26.5 billion tonnes to stay within the 1.5°C limit.

The latest stocktake of the global carbon budget – the amount of carbon that can be emitted before we reach 1.5°C of warming – estimates that we will burn through the remaining carbon budget in about six years. Other estimates suggest that we may have only three years left to reduce emissions sufficiently to limit warming to 1.5°C, and that for a 50% chance of keeping warming to 1.5°C, greenhouse gas emissions would have needed to peak before 2025. Yet, emissions continue to rise and national commitments to reducing emissions remain insufficient. 

Every fraction of a degree of warming increases the odds of additional, and often extreme, impacts. As greenhouse gases build up in the atmosphere, heatwaves are becoming hotter and more frequent and rainfall is becoming more intense and variable. Consequently, droughts and floods are worsening globally, triggering crop failure, infrastructure damage and humanitarian crises.

As emissions continue to rise, it is increasingly likely that our journey to limiting warming will entail a period of ‘temperature overshoot’. Unprecedented efforts are needed, soon, to limit the amount of overshoot and the impacts of temperature rise. 

What is temperature overshoot?

Temperature overshoot is the term used by the Intergovernmental Panel on Climate Change (IPCC) to describe scenarios, or ‘pathways’, in which the Earth exceeds a specified global warming level, typically between 1.5 and 2°C, before returning to that level at some point in the future. 

The magnitude (how much the specified level is exceeded) and the duration (how long it is exceeded for) differ across pathways. In most overshoot pathways, the duration of the overshoot is at least one decade and can extend to several decades, while the magnitude reaches up to 0.5°C. However, in ‘high overshoot’ pathways where the temperature overshoots by as much as 0.5°C, it is unlikely that warming could be returned to ‘well below 2°C’ by 2100. If we follow these high-overshoot pathways, we will not meet the goals of the Paris Agreement.

Most IPCC scenarios foresee some degree of temperature overshoot

Pathways with temperature overshoot are not exceptional. In the IPCC’s Global Warming of 1.5°C report, published in October 2018, 90% of the mitigation pathways that limit warming to 1.5°C by 2100 include a period of overshoot. 
The pathways that limit warming to 1.5°C with limited or no overshoot require deep, rapid and immediate reductions in emissions, with carbon dioxide removal (CDR) only used to compensate for historical emissions and in sectors where no mitigation measures are available.‘2Limited-overshoot’ pathways overshoot 1.5°C by no more than 0.1°C. In comparison, pathways that delay emissions cuts and overshoot the temperature targets rely more heavily on large-scale CDR to bring global temperatures back down by the end of the century.

Explaining 1.5°C scenarios with and without overshoot

Figure 1 illustrates three hypothetical overshoot scenarios for pathways that aim to achieve the 1.5 °C target. In the upper panel, the grey line represents a scenario with no temperature overshoot. The blue line represents a scenario with a low magnitude and short duration of overshoot. The red line represents a scenario with a high magnitude of temperature overshoot that persists for a long time. In the blue and red scenarios, temperatures return to 1.5°C by the end of the century

The lower panel shows emissions trends in each of the pathways. The scenario represented by the grey line reaches net-zero emissions, at which point temperatures stabilise at 1.5°C, by rapidly reducing emissions and without the need for negative emissions solutions. In contrast, the scenarios represented by the blue and red lines require negative emissions solutions, such as large-scale CDR, to reach net-zero emissions. In the red scenario of high and long-lasting overshoot, negative emissions solutions will need to be deployed far beyond the end of the century. 

The greater and longer the overshoot, the more negative emissions solutions will be needed in order to stabilise temperatures at 1.5°C.

Figure 1: Illustration of 1.5°C scenarios with and without overshoot

Source: Reversing climate overshoot, Nature Geoscience 16, 467 (2023).

Increasing overshoot means increasing climate impacts

Every increase in the magnitude and duration of overshoot increases the severity, frequency and duration of climate impacts, such as heatwaves, droughts and floods. In one analysis, the frequency of agricultural drought increases from 24% in a 1.5°C scenario with little to no overshoot to 31% in an overshoot scenario that reaches just below 2°C by the end of the century. In the same scenarios, the frequency of major heatwaves increases from 29% to 44%. Brazil, North Africa, and southern Africa are projected to be the most severely impacted by heatwaves exacerbated by temperature overshoot. 

Sticking to the 1.5°C target also brings economic benefits – climate impacts from temperature overshoot will lead to higher mitigation costs and economic losses later in the century.3While higher initial investments are needed to keep temperatures down, this is outweighed by the economic benefits later in the century. 

For nature, exceeding a temperature threshold for even a short amount of time may push species beyond their tolerance limits, causing extinction, migration and knock-on effects for entire ecosystems. As different parts of the world warm and cool at different rates, species worldwide will be unevenly exposed to dangerous conditions. Temperature overshoot will be particularly critical for species already living close to their thermal limits, such as those in the tropics.

The IPCC estimates that the area of global land at risk of changing from one ecosystem type to another – such as a forest changing to a grassland – is 50% lower at 1.5°C of warming compared to 2°C. Some of the world’s most important ecosystems, such as the Amazon Basin, the Pantanal and the Coral Triangle, could be irreversibly transformed with just a few years of overshoot. 

In the ocean, overshoot is projected to decrease ecosystem habitability for centuries to come. If we do not curtail emissions now, marine ecosystems in the Indo-Pacific, Caribbean and West Africa could experience sudden collapse as early as the 2030s, with knock-on effects for the people who rely on these ecosystems for food and income from tourism. 

Every increment of warming counts

2025 has been hot. It is on track to be the second or third warmest year on record. It is also likely to be the second year since pre-industrial times where the average global temperature exceeded 1.5°C. This occurred for the first time in 2024, which was recorded as the warmest year on record since pre-industrial times and broke multiple heat records on land and in the sea. Although a breach of the Paris Agreement target would require average annual temperatures to be above 1.5°C for at least 20 consecutive years, the fact that we are increasingly seeing individual years surpass this threshold implies that we are getting closer. 

A ‘safe’ limit to global warming does not exist, and we are already seeing devastating impacts at current warming levels. IPCC scientists urge that 1.5°C shouldn’t be viewed as a guardrail. The target of 1.5°C was chosen as a threshold beyond which the impacts of warming become increasingly intolerable to humans and nature. This assessment was made based on criteria such as food security, extreme weather events, health, biodiversity loss, water supply and economic growth. 

But, what is considered an acceptable level of damage from global warming is highly subjective. At just 0.56°C of warming, 506 people died from climate change-induced heat stress in Paris during the summer of 2003. At 0.95°C of warming, wildfires in Australia in 2019-2020 led to the death or displacement of three billion wild animals and caused AUD 4-5 billion in losses to the Australian food system.     

While we have not permanently surpassed the 1.5°C target, we are already experiencing significant impacts of global warming. In 2024, climate change was responsible for an additional 41 days of dangerous heat, and extreme weather events worsened by climate change resulted in the death of thousands of people and billions in damages. These represent only a tiny fraction of all impacts resulting from human-caused warming.

We should do everything in our power to keep warming down as much as possible. As emphasised by IPCC scientist Prof. Mark Howden in 2018: “Every half a degree matters. Every year matters. Every choice matters.”

What are climate tipping points?

Overshooting temperature targets, even temporarily, risks the creation of positive feedback loops – self-perpetuating cycles that speed up warming. These positive feedback loops can trigger climate ‘tipping points’, after which an Earth system transforms into an alternative stable state, completely different to its original state. A single tipping point can have cascading and catastrophic effects at regional and global scales. 

For example, the Amazon is drying and burning due to human-caused warming, which reduces tree cover. Reduced tree cover, exacerbated by deforestation, causes further reductions in rainfall due to decreased evapotranspiration, whereby moisture is evaporated into the atmosphere from trees. Over time, this deforestation-drought feedback loop could pass a tipping point, transforming the region from a rainforest into a savanna. This would switch it from one of the most important global carbon sinks to a carbon source and could trigger potentially catastrophic changes to global rainfall patterns, impacting agriculture.  

The transformation of the Amazon is a fast-onset tipping point, in that when the tipping point is transgressed, the change in the climate system would occur rapidly – in a matter of decades. For these tipping points, overshoot could cause sudden and irreversible changes to the system. Scientists are uncertain when the Amazon’s tipping point might be crossed. Some estimates suggest this could happen at 40% forest loss, and around 26% of the Amazon was already deforested or degraded as of 2022. Some scientists believe that the first warning signals of this shift are already here. 

Other tipping points are slow-onset tipping points, whereby the change to an Earth system occurs over a much longer timescale, like over many centuries. For these tipping points, briefly overshooting temperature targets might not cause immediate and irreversible changes to the climate system, as long as the overshoot is not longer than the time needed for the system to recover. One example is the melting of the Greenland ice sheet. While we may be close to this tipping point, it is estimated that ice sheet loss could be mitigated as long as temperatures are brought back down to 1.5°C or lower relatively quickly once the tipping point is reached.Even temporary overshoot increases the risks of surpassing critical tipping points by 72% compared to scenarios with no overshoot. Keeping the magnitude and duration of overshoot as low as possible is critical and rapid decarbonisation is key: While delaying emissions reductions to beyond 2030 could still allow us to meet 1.5 °C by the end of the century, this would result in higher temperature overshoot over many decades, with the potential for adverse consequences.

Boundaries for keeping the Earth habitable

Humans have altered the Earth, such as by depleting the ozone layer, reducing biodiversity, changing land cover and warming the atmosphere. Scientists have tried to estimate how far these processes could continue to be altered until a global tipping point is reached, causing the Earth to transform irreversibly into a state that could endanger humanity and render the planet uninhabitable.

Planetary system boundaries

The concept of planetary system boundaries involves tracking changes to nine crucial processes, identified by scientists as responsible for keeping the Earth habitable (Figure 2). These processes are ranked on a scale from ‘safe operating’, meaning the process happens in a way that is safe for humanity, to ‘high-risk’, i.e. the process poses a high risk to humanity.Of the nine identified planetary boundaries, the Earth is now outside the safe zone for seven: Climate change, biosphere integrity (the quality of living organisms and ecosystems, impacted by, for example, decreasing species diversity), land-use change, biogeochemical flows (for example of nitrogen and phosphorous – aggravated by agribusiness and industry), novel entities (the release of novel chemicals such as plastics), freshwater change and ocean acidification. The safe space for ocean acidification was added as breached in September 2025, reflecting worsening trends.   

Figure 2: Planetary system boundaries 

Source: Seven of nine planetary boundaries now breached – ocean acidification joins the danger zone, Potsdam Institute for Climate Impact Research (2025)

There is great scientific uncertainty regarding how much longer we can continue to push these boundaries before the total collapse of the Earth’s system happens. However, if we rapidly decarbonise, we could reduce this risk and stabilise the Earth within a safe operating space. 

Earth system boundaries

Scientists have also proposed a set of ‘safe and just’ Earth system boundaries that quantify the safety of humans and the stability of the planet (Figure 3). Safe boundaries are those “where biophysical stability of the Earth system is maintained and enhanced over time, thereby safeguarding its functions and ability to support humans and all other living organisms”. Just system boundaries minimise the exposure of countries, communities and people to significant harm, including “loss of lives, livelihoods or incomes; displacement; loss of food, water or nutritional security; and chronic disease, injury or malnutrition”. 

This framework differs from previous frameworks in that the impacts on people are measured in comparable units to impacts on the planet. While other frameworks only assess how human activities have impacted Earth systems, using comparable units allows for a better understanding of the harm that changes to Earth system boundaries will do to humans. The framework focuses on all species, not just humans, attempting to “define the environmental conditions needed not only for the planet to remain stable, but to enable societies, economies and ecosystems across the globe to thrive”. The framework also incorporates information on climate, the biosphere, and other Earth system tipping points into the Earth system boundaries

Figure 3: Safe and just Earth system boundaries

Source: Safe and Just Earth System Boundaries published in Nature, Global Commons Alliance (2023).  

According to this framework, the ‘just’ Earth system boundary for climate is 1°C, while the ‘safe’ boundary is 1.5 °C. The Earth has already heated by more than 1.2 °C, meaning current global warming, while still in the ‘safe’ zone, is unjust (Figure 3), emphasising the need for urgent action. As the framework incorporates interspecies justice, intergenerational justice and intragenerational justice (including race, class and gender), it can be used to inform sustainability targets and practices. 

However, these frameworks have been criticised, with some suggesting that they are too simplistic or that they do not distinguish between thresholds, that can be breached, and hard limits, that cannot be breached. They may also shift political focus to the wrong areas or dampen political action. Others warn against allowing one group of scientists to define what constitutes a safe set of boundaries for everyone on the planet, which could be viewed as divisive. 

Relying on carbon removal is risky – emissions cuts must come first

To bring average global temperatures back down to between 1.5 and 2°C, overshoot scenarios rely to different extents on CDR. This includes nature-based solutions, such as afforestation (planting forests) and bioenergy with carbon capture and storage (BECCS). Other solutions include direct air capture (DAC) and storage, where CO2 is directly captured from the air and then stored for the long term. 

However, there are major risks and uncertainties with these approaches. With nature-based CDR and BECCS, there is a risk that ecosystems could be replaced with bioenergy crops or plantations, endangering wild plants and animals. Food crops could be supplanted, threatening food security. DAC technology is still in its infancy. These technologies are also not proven to be effective at the scale needed. 

These uncertainties and risks emphasise that climate action needs to be boosted in the near-term to reduce our reliance on these approaches for bringing temperatures back down later in the century. 

Geoengineering cannot replace rapid and deep emissions cuts

Rapid and deep emissions cuts provide the best chances of limiting temperature overshoot and avoiding tipping points. At the same time, approaches that remove carbon from the atmosphere can help to offset emissions that cannot be reduced and mitigate overshoot. 

Technologies that aim to intervene with Earth systems at a large scale to counteract the effects of a warming climate, referred to as geoengineering, have also been increasingly proposed in recent years.4CDR is also defined as a geoengineering approach by the IPCC. A prominent solution is solar radiation management (SRM), which aims to reduce the amount of sunlight absorbed by the Earth by reflecting it back into space or preventing it from reaching the Earth’s surface altogether. This would result in reduced warming, but would have no impact on greenhouse gases that are being released into the atmosphere or that are already there, meaning it does not tackle the underlying causes of climate change and instead introduces new and additional risks. 

Research remains in early and theoretical stages, with many unknowns and potential unintended consequences. Studies suggest that SRM would have significant impacts on water cycles, could modify monsoon systems, and could lead to drought in some tropical regions. SRM could also impact renewable energy generation, which is crucial for mitigating emissions. Additionally, as its deployment would impact the climate of the entire planet, SRM comes with substantial geopolitical risks. 

SRM approaches would have to be implemented continuously until emissions are reduced to safe levels to prevent warming. If they are stopped before this happens, this would result in very rapid warming, and “severely stress ecosystem and human adaptation”, according to the IPCC. The IPCC is very clear that, even in best-case scenarios, SRM is a supplement to rapid and deep emissions cuts. 

Positive tipping points can help us reach net zero

In contrast to climate tipping points, positive tipping points – otherwise known as positive socio-economic tipping points – occur when a set of conditions is reached that can accelerate the deployment of technologies or practices to achieve net zero. For instance, a new technology begins to outcompete an old technology. Sales of the new technology facilitate further development, which in turn reduces its costs, allowing the new technology to become widespread and replace the old. An example of this is the rapid development of renewable energy, where over just 10 years, solar and wind technologies have become the cheapest source of power in many parts of the world.   

Targeted interventions in socioeconomic, technological and political systems can be used to advance climate change mitigation, and strategic investment can help bring down the costs of technologies that facilitate decarbonisation. For example, oil and gas companies have been accused of having overly optimistic projections of long-term oil prices, resulting in an inflated picture of future economic performance. Updating the accounting standards or disclosure guidelines for these companies could cause prices to decrease, thereby curbing investment and catalysing investment into renewables. 

The focus on these positive tipping points should not distract us from the need to rapidly decrease emissions. Rather, these positive tipping points should be viewed in the context of driving strategic interventions to encourage decarbonisation.

This briefing was originally published in December 2023. This updated version was published in October 2025.

Hope and hype | Standard setters | Land fights

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Dear all,

2025 started with a slew of catchy headlines about the scope and profitability of carbon dioxide removal (CDR), including the New York Times calling it “the new climate gold rush”. This month, we look at how the expansion of the removals market compares to these high expectations.

We also review new draft standards set by the Science Based Targets initiative (SBTi) that may further increase demand for removals. Some believe this could send a strong market signal for investment in the industry. But, at the same time, new research has reiterated the importance of reserving CDR for emissions that cannot be avoided and prioritising decarbonisation. 

On nature, we look at the challenges and uncertainties of using afforestation and forest conservation to capture carbon. A new paper highlights the tension between using land for food and carbon sequestration and food security, especially in the Global South. 

As always, please feel free to share this newsletter with anyone who may be interested. You can sign up here, and don’t hesitate to get in touch if you have any questions, suggestions or feedback.

Till next time,

Victoria

Hope and hype

2025 started with some bold headlines about CDR, especially in the US. The New York Times referred to it as “the new climate gold rush” – an opportunity for venture capital – and Nora Cohen Brown, Head of Market Development and Policy at CDR company Charm Industrial, described it as “The Great New American Industry” in Forbes. 

Plans for increasing capacity and forecast market growth are fueling optimistic takes. At the end of last year, New Scientist wrote that “Direct CO2 capture from the atmosphere will scale up massively in 2025” due to the planned opening of the Stratos direct air capture (DAC) facility in Texas, the biggest in the world.  A report published in March projected that the market for engineered CDR credits will surpass USD 14 billion in 2035, suggesting that the recent 40,000 tonne deal between Climateworks and investment bank Morgan Stanley and the anticipated completion of Project Stratos will help the sector towards the “milestone” of one million tonnes of carbon removals in 2025.

However, CDR deployment remains slow and the future impact of what can be achieved is uncertain. As with any emerging industry, anticipating challenges and keeping hype in check is key. CDR purchases have risen, increasing by 59% to USD 3.4 million between 2023 and 2024, but the delivery of CDR credits – i.e. actually completing the promised removal – remains low. According to CDR.fyi, currently only 4.66% of the 13 million tonnes of CO2 removal credits sold worldwide have been delivered.

“CDR deployment remains slow and the future impact of what can be achieved is uncertain. As with any emerging industry, anticipating challenges and keeping hype in check is key.”

A recent survey from CDR.fyi revealed that 55% of CDR suppliers haven’t sold a credit and 73% haven’t delivered one. This creates supply uncertainty and, according to Forbes, could cause buyers and investors to hesitate. Industry experts have suggested that the industry may face a plateau in the next 2-3 years stemming from a lack of anticipated purchases.

Plus, the finite potential for carbon removal must be kept in mind. Recent research reiterated that CDR needs to be used exclusively to compensate for hard-to-abate emissions and overshoot, to “prevent lower costs for near-term actors leading to larger long-term system-wide costs.” The research looked at how much CDR would be needed in future pathways that enable warming to return back to 1.5 °C after temporarily overshooting it at the lowest cost, finding that 78 of 81 scenarios require all available “sustainable” CDR (referring to afforestation, reforestation and BECCS) be used to compensate for “hard-to-abate” emissions and overshoot.

Recent research by the American Physical Society has also given the physical science take on what is needed for implementing large-scale CDR. They highlighted that to remove one billion tonnes of CO2 – “just 3% of what humans add every year” – the systems “would need to process the same amount of air that all the air conditioners in the world currently process in one year.” Despite the mass energy and resource use, the report’s authors acknowledged that CDR could be necessary in future, recommending that research and development investments should be pursued “selectively and prudently.”

Trump watch 

There have been drastic governmental changes in the US following Trump’s inauguration in January, with the Department of Energy (DoE) being no different. By February, the Department of Energy’s Carbon Dioxide Removal Team had been hollowed out down to one remaining worker, according to Heatmap News. 

This raises uncertainty about the implementation of DAC programmes, including two large-scale projects in South Texas and Louisiana and around 19 smaller hubs in earlier stages of development. The two large hubs are part of a list of Biden-initiated programs at risk of being erased under Congress’s budget reconciliation bill to fund tax cuts, which is currently under review by Energy Secretary Chris Wright. Of the USD 550 and USD 500 million the hubs were awarded, they have only received USD 50 million thus far. 

In the context of the US’s chaotic and uncertain funding landscape, Jorden Dye, director of the Pembina Institute’s CDR Centre, suggested that Canada can step in, take the lead and hit the CDR targets the US will now fail to meet. Dye highlights that three provinces and the federal government have already launched “consultations to integrate CDR within their carbon compliance systems and establish regulations for carbon storage” in the last three months.

In the EU, recommendations on scaling up CDR were recently released by the European Scientific Advisory Board on Climate Change. Companies claim CDR could help EU competitiveness and reports from Germany, the Netherlands and France outline potential strategies for ramp-up.

BECCS vs land

Countries have to submit nationally determined contributions (NDCs), or national climate pledges, as part of the Paris Agreement, which include targets for land systems and nature-based solutions – but what do these mean in practice?

While some earlier studies estimated that climate mitigation could allow future cropland expansion to feed growing populations, a new paper in Nature Climate Change found that implementing national pledges would result in a 12.8% reduction in cropland area. This is mainly due to the conversion of low-density crop areas to make way for forest plantations and reforestation. The impacts are most pronounced in the Global South, where 81% of the countries expected to experience cropland loss are located and many regions are already facing the brunt of food security issues.

Biomass for bioenergy with carbon capture and storage (BECCS) is included in some NDCs and is heavily relied on in climate models that limit warming to 1.5°C. At the end of March, Swedish energy company Stockholm Exergi announced that it will build one of the largest BECCS plants in the world. 

Growing crops for use in BECCS also requires land. For the first time, a new report has explored how BECCS could impact planetary boundaries, which represent the safe limits for life on Earth. The researchers concluded that if BECCS crops are planted beyond the land currently used for agriculture, only a very small amount – much less than is assumed in many climate scenarios – could be achieved before it would endanger the stability of the biosphere. Six of the nine planetary boundaries have already been crossed, meaning the Earth is already outside the “safe operating space for humanity”.

Forestry uncertainty

Planting forests (called afforestation) involves deciding what to plant and where. New research found that in the UK, the best planting strategy for a high-emission future is very different to that for a future “that remains on a ‘near-historic’ path.” Planting decisions need to be made with future uncertainty in mind, and making the wrong decisions could lead to net costs. The researchers highlighted that diversifying species and planting locations can help reduce risks and increase the chances that the plants remain resilient. 

Despite the uncertainty, the researchers maintained that tree planting is still a very effective way of removing carbon in the UK. This sentiment is shared in an article (not linked to the study) that suggests AI companies invest in nature-based solutions instead of gambling “on complex, expensive and risky technologies” in the context of the AI-driven CDR boom.

Planting more trees is good and well, but ultimately it won’t make a dent in warming unless we rapidly reduce emissions now. Recent research assessed a wide variety of possible CDR routes to return warming to 1.5°C,  or even 1°C. For this to be possible via large-scale deployment of removal technologies, “a transition towards 100% renewable energy must be the number one priority” to enable technologies to be run on renewable energy. 

Plus, biodiversity seems to be being left as an afterthought in afforestation efforts. A new paper found that most initiatives that restore forest cover are focused on “achieving utilitarian functions over biodiversity gains”, often with plantations of one or few tree species and carbon sequestration prioritising thinking. Inappropriate reforestation projects have also resulted in detrimental outcomes for natural areas. Afforestation and forest restoration have the potential to be winning strategies due to the co-benefits they can provide for ecosystem services and biodiversity. The authors highlight that there are many opportunities to bring biodiversity to the forefront of planning if clear biodiversity goals are defined, alongside adequate monitoring and sustained funding.

More on minimising trade-offs:

  • A study released early this year modelled the trade-offs of using different carbon removal approaches, finding that using a mix of different methods was the most cost-effective net-zero strategy. In specific regions, such as Latin America and Africa, nature-based removals offer the most benefits, not only in terms of carbon removal but also for “preserving planetary well-being and human health.”
  • A study looking at the US echoed this finding that when more CDR technologies were available, side effects on energy, land and material supplies were less pronounced. The authors highlighted the importance of using approaches “tailored to each state’s unique economic and industrial characteristics to ensure equitable and effective decarbonization strategies.”

Standard setters

In late March, the Science Based Targets Initiative (SBTi) released the first draft of its new Corporate Net-Zero Standard, which aims to give business leaders clarity on developing decarbonisation plans aligned with climate science. The draft outlines carbon removals as a way to mitigate “hard to abate” – or residual – emissions and proposes three options for interim targets on how carbon removals can be used to address residual emissions. This is a change from the existing Standard adopted in 2021, which only permitted the use of carbon credits, including CDR, to neutralise residual emissions for net zero once a company has reached its net-zero target. 

Net zero standards, such as the ones set by SBTi, could have a substantial impact on the CDR market. Survey results from CDR.fyi indicate that “Sixty-five percent of respondents pointed to clearer net-zero standards… as the primary motivator for buying durable carbon credits.” Caroline Ott, director of carbon markets at Climeworks, told the Wall Street Journal she “absolutely think[s] this is a driver” for prospective customers. 

However, some believe the change, which only relates to “scope 1” or companies’ direct emissions, will not be enough to generate demand for a durable CDR industry (Heatmap News points out that less than 1% of Apple’s emissions are scope 1, for example). 

Plus, the standard assumes that companies will eventually have to start removing carbon when they hit net zero, which should be before 2050, but companies can decide whether or not they want to invest in carbon removal in the interim. Companies may have interpreted it as “they shouldn’t or don’t have to buy carbon removal credits until 2049,” Lukas May, the chief commercial officer and head of policy at Isometric, a carbon removal registry, told Heatmap News, which could threaten investment needed by the industry now for it to scale up before 2050. 

Recently companies have retreated from environmental, social and governance (ESG) strategies – more so since Trump began his presidency – causing uncertainty around the impact of SBTi and other ESG standards. At the end of last year, only 43 of the top 200 companies in the world had SBTi targets. 

Pick of the news 

Is carbon capture a solution to the climate crisis? (CBS News) 

“You have to think about who’s proposing this technology,” Jacobson [Professor of environmental engineering at Stanford University] said. “Who stands to benefit from carbon capture and direct air capture? It’s the fossil-fuel companies.”

Why carbon markets aren’t enough to scale carbon removal (Latitude Media) 

Moving beyond carbon credits could help CDR, for example by finding a market for the additional benefits of CDR approaches beyond sucking up carbon so they become a “stand-alone, scalable and cost-effective practice”.

AI’s energy problem: Why carbon removal can’t wait (World Economic Forum)

CDR companies caution that a shortfall of clean energy compared to demand from AI companies “means unavoidable emissions, which makes carbon removal not just a corporate responsibility, but a fundamental requirement for AI’s continued growth.”

Saudi Aramco launches first direct air capture test unit (Reuters)

Saudi oil giant Aramco has unveiled a test DAC plant, which the company says is a first step in scaling up viable DAC systems in “Saudi Arabia and beyond”. 

Net-Zero Asset Owner Alliance to ‘advance work’ on financing CO2 removal (Responsible Investor)

Along with the new SBTi standards, The UN-convened Net-Zero Asset Owner Alliance (NZAOA) is also anticipated to release guidance on best practices for investors to finance CDR and compensate for residual emissions soon.  

Net-zero progress overblown by inconsistencies in land carbon accounting

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Key points:

  • Nationally Determined Contributions (NDCs) – which outline national governments’ commitments to emissions reduction – account for land-based carbon removal using different methods to the IPCC. 
  • When the methods are harmonised, NDCs reduce the budget for limiting warming within Paris Agreement goals by 15-18%, equivalent to bringing forward the deadline for net zero by five to seven years. 
  • This means governments need to set far more ambitious mitigation targets to achieve net zero as defined by the IPCC, than covered by their current methods.
  • Differences in how emissions are reported from managed and unmanaged land in NDCs compared to the IPCC introduces opportunities for bias or misrepresentation, obscuring countries’ true climate impacts.
  • The amount of land designated for land-based removals in NDC pledges – about 1 billion hectares or the equivalent of around two-thirds of global arable land – is also impossible without complex trade-offs for food security, biodiversity and human livelihoods.
  • IPCC models give unrealistically optimistic estimates of land-based removal potential because they don’t consider land availability constraints, conflicts and human rights issues, or the erosion of land carbon sinks.
  • By comparison, a recent analysis modelling the social and ecological risks of land-based carbon removal potentially reduces the amount of land available for carbon removal by up to 79% compared to IPCC estimates.   
  • This discrepancy suggests that status quo estimates of land-based carbon removal used to inform global and national climate ambition may be overblown and misleading.

Emissions reduction in NDCs

Under the Paris Agreement, adopted in 2015, countries around the world agreed to submit climate action plans called Nationally Determined Contributions (NDCs) every five years starting in 2020 to address greenhouse gas emissions.1Each new NDC submitted needs to be more ambitious than the last. NDCs translate global agreements into specific national targets and are the key mechanism for countries to show their commitment to reducing emissions – through, for example, phasing out fossil fuels, deploying renewable energy, decarbonising industries and electrifying transport.

Another approach to reducing emissions involves harnessing the ability of landscapes to capture and store carbon – a greenhouse gas inventory sector referred to as land use, land-use change, and forestry (LULUCF) by the Intergovernmental Panel on Climate Change (IPCC).2LULUCF excludes non-carbon-dioxide agricultural emissions, such as methane from livestock. Natural landscapes around the world store significant amounts of carbon in plants and soil – global forests absorb an average of 7.6 billion metric tonnes of carbon dioxide per year, equivalent to around one and a half times the annual emissions of the US. 

In the LULUCF component of their NDCs, countries pledge to plant new forests (afforestation), restore degraded forests (reforestation), protect existing forests and implement sustainable forest management and soil conservation techniques. To a much lesser degree, they also project the use of bioenergy with carbon capture and storage (BECCS), whereby trees, crops or algae will, in theory, be grown to capture carbon dioxide from the atmosphere and then converted into energy, such as biofuels, with the emissions stored below ground.

These forms of carbon dioxide removal are appealing to governments and industries because they don’t necessitate immediate, large-scale changes to a country’s industrial and energy sectors.  However, although most IPCC pathways that aim to limit warming to Paris Agreement targets of 1.5°C or 2°C include carbon sequestration in land sinks, enhancing these sinks alone is insufficient to achieve the necessary carbon reductions. Ambitious and timely NDC commitments this decade could close the emissions gap needed to keep temperatures within targets but require a rapid shift away from traditional fossil fuels in addition to land-based removal. 

Due to several scientific and political reasons outlined below, the potential contribution of land carbon sequestration to emissions reductions is significantly overestimated in NDCs and scientific models. This overestimation renders the commitments outlined in NDCs unrealistic and endangers the goals of the Paris Agreement. While several publications have explored this issue, no comprehensive, easy-to-read resource has been created to synthesise the findings. The goal of this briefing is to provide a concise summary of the various reasons NDCs disproportionately rely on land for carbon removal and to outline the potential implications for the Paris Agreement.

Land carbon fluxes are the most uncertain component of the global carbon budget

Countries annually report their progress on the emissions reductions pledged in their NDCs through National Greenhouse Gas Inventories (NGHGIs), following guidelines established by the United Nations Framework Convention on Climate Change (UNFCCC). 

Collective progress towards the Paris Agreement goals is assessed every five years in the Global Stocktake, which provides benchmarks for countries for their NDC submissions. If NDCs are insufficient or lack ambition, there is a significant risk that the world will exceed the Global Carbon Budget – the total amount of carbon dioxide that can be emitted while keeping within global temperature targets, leading to temperature increases beyond the targets agreed upon in the Paris Agreement.

Because of the complex interactions of various human-driven effects on greenhouse gas fluxes from land – such as deforestation for agriculture – land carbon fluxes are the most uncertain component of the global carbon budget. At the national level, accurately tracking changes in forests and other land uses is also challenging due to variations in the quality and scope of land-use data, different reporting methods used, and difficulties in separating the influence of humans and climate on the environment as well as in reporting carbon movements in different ecosystems, with estimates relying significantly on simplified models. This means that estimates of emissions from LULUCF are less precise than those from fossil fuels, which are grounded in empirical data.

As a result, the Paris Agreement allows flexibility for countries to determine how they account for emissions and removals from the LULUCF sector, such as the use of different accounting and monitoring methods or different definitions of land-use types in their climate targets. In addition, developing countries are encouraged to gradually adopt economy-wide emission reduction targets depending on their economic and developmental needs. In comparison, developed countries are required to specify a specific, measurable and economy-wide reduction in overall emissions – for example, a 40% emissions reduction compared to 1990 levels.

NDC net-zero may not mean net-zero global emissions

The use of different carbon accounting methods for land-based removal between NDCs and model-based methods, such as those used by the IPCC, makes it hard to measure the emissions and temperature outcomes of current national commitments under the Paris Agreement. 

While both NGHGIs and the models used by the IPCC to assess the pathways necessary to achieve specific climate targets aim to identify greenhouse gas fluxes from land, they differ in how they account for the role of human activity in these fluxes. This affects the extent to which each approach attributes these fluxes to a country’s mitigation efforts.3One outcome is that estimates of land-use change due to afforestation or reforestation are in close agreement between NGHGIs and IPCC models, but differ for managed forests.

This is especially problematic for countries that rely heavily on the land sector and forest management to achieve their NDCs, leading to over- or under-estimating true emissions and creating inconsistencies between national inventories and the global carbon budget.

A recent analysis illustrated how current NGHGIs for NDCs can make national emissions appear lower than the method applied by the IPCC in assessing alignment with the Paris Agreement. It concluded that once the methods are harmonised – such as by adjusting fluxes from land use – our overall carbon budget is reduced by 15-18%, which is equivalent to bringing forward the deadline for net zero up by five to seven years. What this means is that governments need to set far more ambitious mitigation targets to achieve net zero, as defined by the IPCC.

Unmanaged land is a blind spot in carbon accounting

Discrepancies in the LULUCF emissions estimates between IPCC models and NDCs arise partly because countries are not required to report emissions from unmanaged land – such as emissions from wildfires in remote forests where human intervention is minimal or absent – as these are considered natural rather than human-caused emissions. This has resulted in some highly forested countries designating large areas of forest as unmanaged. But as emissions are still released from these unmanaged areas, excluding them leads to an incomplete picture of the carbon cycle and a country’s total emissions.

This has introduced opportunities for bias or misrepresentation. For example, Canada does not include emissions from forest wildfires in its inventory, as around 34% of its forests are classified as ‘unmanaged’. This means that emissions from natural disturbances, such as wildfires, in these forests are not accounted for.4The Canadian government does not have a database for the net carbon flux in unmanaged lands in the country, making it difficult to track carbon emissions and evaluate whether Canada’s landmass is sequestering enough carbon to offset its emissions. Additionally, fires within its managed forests are also classified as natural disturbances rather than human-caused disturbances, and so are also excluded from the inventory.

This oversight leaves significant emissions unaccounted for, obscuring Canada’s true climate impact. Around 114 million metric tonnes of emissions was excluded per year from its inventory between 2005 and 2021 – equivalent to around half the total carbon dioxide emissions from gas in Canada in 2023.5This is compounded by the fact that Canada classifies removals from mature forests as human-caused. In 2023, a year of record-breaking wildfires, natural disturbances released an estimated 640 million metric tonnes of carbon from Canada’s forests, which is more than Canada’s carbon dioxide emissions from fossil fuels in 2022.

Managed land can lead to overestimates of climate progress 

Flexible guidelines also mean that there is variation in what constitutes managed and unmanaged land. Under the Kyoto Protocol adopted in 1997, countries agreed to count greenhouse gas emissions and removals from land activities towards their climate targets only if they result from direct human actions. However, the IPCC later noted that as human activities and environmental changes are closely linked, they are not practical to separate in greenhouse gas inventories – for example, forest loss from both logging and climate-induced drought. Therefore, ‘managed land’ was introduced as a proxy for human effects in NDC guidelines, with all greenhouse gas fluxes occurring on managed land being counted regardless of whether they are driven by humans or the environment. This is not a feature of the IPCC’s models that are used for estimating carbon fluxes, which clearly distinguish between emissions from managed and unmanaged forests. 

This means that countries can classify natural forests as managed land in their NGHGIs, enabling them to report natural carbon removal as emissions reductions. Including natural land as managed land can also give a misleading picture of a country’s actual climate efforts by overestimating carbon removals and making progress seem greater than it is. This is further aggravated by the fact that some countries – particularly those that are afforded flexibility in emissions accounting – also report implausibly high forest sinks, have incomplete assessments or have inconsistent estimates across reports. Some forest-dense countries are claiming credit for the carbon that their unmanaged forests are sequestering, using this as a means to justify fossil fuel extraction while also making net-zero claims.

Land-based removal plans are unrealistic

The lack of stringent accounting guidelines has led to a significant over-allocation of land for carbon removal in NDC pledges, beyond what is technically feasible or safe. The Land Gap Report calculated that there is about 1 billion hectares of land for land-based carbon removal included in NDC pledges to 2060 – equivalent to around two-thirds of the world’s arable land and a land area bigger than China. Such large-scale commitments would be impossible without catastrophic impacts, including the displacement of food production and threats to biodiversity. 

Pledges for land-based removal in NDCs rely heavily on planting new forests or plantations, with about half of the land proposed for carbon removal in NDCs requiring changes in present land use. Land-use change is already the biggest driver of biodiversity loss, which is essential for ecosystem resilience and the provision of ecosystem services such as food and water security and carbon sequestration.6Agricultural land is already under significant pressure from rising global food demand, expanding populations and the need to balance land use with biodiversity conservation and climate mitigation efforts. A 2022 analysis estimated that afforestation and bioenergy production could place an additional 41.9 million people at risk of hunger by 2050 due to higher food prices and displacement of agricultural land

In addition to the risks around increased competition for land use, estimates suggest that the ‘safe limit’ for expanding agriculture has already been passed, resulting in ecosystem degradation. Figure 1 shows that global cropland already exceeds the planetary boundary for sustainable land use, with land-use changes in pledges and current and projected BECCS projects adding nearly an extra two-thirds to the current land-use change area. There is very little land left that can be used for carbon dioxide removal without complex trade-offs. To be genuinely effective, carbon removals plans need to factor in ecological limits and support biodiversity.

Figure 1. Land for mitigation crosses planetary boundary thresholds
Source: The Land Gap Report, 2022.

Even if the estimates of removal potential from land in NDCs were technically feasible, a 2023 analysis calculated that current NDCs are insufficient for meeting Paris Agreement targets – actions outlined in NDCs are due to result in warming of 2.5-2.9°C by 2100.

Limitations in IPCC models of future land carbon removal 

While NDCs focus on near-term actions to reduce greenhouse gas emissions, Integrated Assessment Models (IAMs) used by the IPCC project long-term scenarios for achieving climate goals. IAMs assess the interactions between climate, energy, land use and economic systems to understand the long-term implications of different policy choices and emissions trajectories, offering different pathways that illustrate how various strategies can achieve climate targets. IPCC pathways offer a framework for countries to set their emissions reduction targets and to align their NDCs to demonstrate their commitment to international climate agreements.

However, recent research argues that the methodologies in IPCC models are over-relying on land-based removal by building in assumptions about land use that are unrealistic. The models do not reflect real-world conditions such as land availability, lack nuance by failing to capture the complexities of human systems and ecosystems, and expose vulnerable communities to avoidable risks. As IPCC reports are the primary mechanism informing the UNFCCC, inappropriate models have the potential to lead to misguided policies and ineffective climate action, ultimately hindering efforts to reduce greenhouse gas emissions and meet international climate goals.

Hidden assumptions mean models over-rely on land

A key challenge with the representation of land-based carbon removal in IAMs is the assumption that significant emissions generated in the near term will be offset in the distant future through decades of land-based removal. 

Because of their emphasis on cost-effectiveness, least-cost pathways and supply-side technologies, IAMs often assume that large-scale BECCS and afforestation projects can be implemented easily, without considering competing demands for land. This leads to overestimations of the amount of land available for future carbon removal in the LULUCF sector. To demonstrate this, a 2018 study assessed the rate at which land uses change in IAMs and found that in scenarios limiting warming to 2°C by 2100, cropland for BECCS is projected to expand by 8.8 million hectares per year. This expansion rate is more than three times as fast as the historical expansion of soybean, which is currently the fastest-growing commodity crop and a significant driver of deforestation in the Amazon. 

IAMs also have idealised assumptions that do not fully consider the technical, social and economic barriers to scaling up such efforts, such as land tenure issues, governance challenges, the potential for conflict over land use​ and human rights issues, including rights to food, water and a healthy environment. 

IAMs are built on assumptions of ‘empty land’ that do not consider nomadic or Indigenous lifestyles or non-forest ecosystems, such as savannas, and also broadly assume that forests can be converted to cropland for bioenergy. BECCS only features in the NDCs of seven countries, totalling 80 million hectares of land, but it is much more prominent in modelled IPCC pathways, with a median land demand of 199 million hectares (ranging from 56 million to 482 million hectares) in 1.5°C-consistent pathways. However, given such a significant land demand for BECCS from a small number of countries in current NDCs, a land demand of 199 million hectares in future pathways is likely to be an underestimate if BECCS becomes as widespread as in modelled pathways.

The models have also been criticised by researchers for being opaque, with specific value judgments about the future buried in the mathematics of the model. By assuming that the financial costs of mitigation technologies will fall in the future – through applying a high discount rate in the model – solutions like BECCS, which has not yet been proven to work at scale, can appear more cost-effective than proven, readily implementable actions. As BECCS is considered ‘carbon neutral’ in the models, many IAMs also favour large-scale BECCS over renewable technologies to meet the requirements of one of the more ambitious climate pathways that assumes significant reductions in greenhouse gas emissions.7The RCP 2.6 emissions pathway in the IPCC’s Sixth Assessment Report.

A 2024 analysis found that a high discount rate in IAM models favours high overshoot scenarios – where global average temperatures temporarily exceed a warming target before dropping back down to, or below, the target in the future – rather than scenarios that would mitigate long-term warming effects. This is because of the short timescale over which economic adaptation is assessed in the models. These high overshoot scenarios result in a heavy reliance on land-based carbon dioxide removal in the future as emissions are not reduced fast enough to limit warming. Overshoot is estimated to be cheaper than longer-term solutions and is therefore favoured by the models. However, overshoot comes with various risks and uncertainties, such as species extinction and ecosystem collapse, and has potentially irreversible consequences. Overshoot also raises moral concerns, as climate-related impacts disproportionately affect vulnerable populations, especially in low-income countries.

Reliance on land carbon removal raises sustainability risks

A recent analysis proposed thresholds for land-based sequestration that account for social and ecological risks, thereby developing realistic and sustainable estimates for land-based CDR while accounting for environmental and resource limits (Table 1).​ The analysis estimates that the sustainable potential of LULUCF measures for carbon removal, including limited reforestation, forest restoration, reduced forest harvest, agroforestry and silvopasture, and BECCS is  3.3 billion-3.8 billion tonnes per year.8Values obtained from Supplementary Table S1 in the report.

The study finds that at high sustainability risk – the point at which multiple ecological and social sustainability limits are likely to be overstepped with potentially irreversible consequences – the value is 6.4 billion tonnes per year. These estimates of sustainable – and hence feasible – removal potential are more conservative than the average estimates in the IPCC’s Sixth Assessment Report – 15.6 billion metric tonnes of carbon dioxide per year between 2020 and 2050 for BECCS, forest and ecosystem protection, restoration and management, and agroforestry, as well as the Emissions Gap Report which included estimates of 5.9 billion tonnes per year by 2030 and 8.4 billion tonnes by 2035 for forestry-related land management,9Values obtained from Table 6.2: Sectoral mitigation potentials in 2030 and 2035. and the State of CDR Report at 7 billion-9 billion metric tonnes by 2050 from forestry-related removal, BECCS, ecosystem restoration and novel technologies such as direct air capture. Compared to IPCC estimates, a low sustainability risk scenario potentially reduces land available for carbon removal by around 79%.10This is a rough calculation assuming a direct comparison between land-use footprint in the IPCC technical mitigation potential and the analysis in Deprez et al. (2024) and was calculated as the difference between the IPCC estimates of 15.6 billion metric tonnes and the lower sustainability risk estimate of 3.3 billion tonnes.

Overall, the greatest risks are linked to scenarios with slower emission reductions and higher reliance on future carbon removal technologies. This highlights the need to reduce emissions quickly and significantly and not rely on future carbon removals – including from land – in order to avoid the worst outcomes.

Table 1. Sustainability risks for land-based carbon dioxide removal for the five IPCC Illustrative Mitigation Pathways compatible with the Paris Agreement.
Data source: Sustainability limits needed for CO2 removal, 2024.  
A/R refers to afforestation/reforestation. BECCS & A/R larger footprint assumes a low capture rate and conversion efficiency, while BECCS & A/R medium footprint assumes a medium capture rate and conversion efficiency.
Models do not account for land’s declining ability to store carbon

As IAMs are global in scale, their assumptions are simplified and generalised, and therefore they can miss key local dynamics, leading to ill-suited projections at the regional level​.11The IPCC recommends that these models are interpreted in the context of their assumptions. IAMs often oversimplify ecosystems, which do not always behave linearly in response to human activities or climate change. For instance, land-use changes can trigger feedback loops that are difficult to capture accurately in simplified models. A 2024 analysis found that IAMs tend to underestimate the risks associated with the interaction between wildfire disturbances and climate change, particularly regarding their impact on the ability of forests to sequester carbon, risking an overly-optimistic estimate of how much carbon forests can remove and store, and inaccurate predictions of future emissions​.

This is significant because land and ocean sinks are increasingly absorbing less carbon with rising temperatures. In higher emissions scenarios, the interaction between climate change and the carbon cycle becomes more uncertain due to the risk of positive feedback loops – such as forest fires and permafrost thaw – amplifying climate change impacts. These types of ecosystem responses are not fully integrated into models simply because of their sheer complexity. While models have tended to predict a slow erosion of natural carbon sinks over the next 100 years or so, other estimates suggest that the impact from feedback loops is happening much sooner than anticipated.

  • 1
    Each new NDC submitted needs to be more ambitious than the last.
  • 2
    LULUCF excludes non-carbon-dioxide agricultural emissions, such as methane from livestock.
  • 3
    One outcome is that estimates of land-use change due to afforestation or reforestation are in close agreement between NGHGIs and IPCC models, but differ for managed forests.
  • 4
    The Canadian government does not have a database for the net carbon flux in unmanaged lands in the country, making it difficult to track carbon emissions and evaluate whether Canada’s landmass is sequestering enough carbon to offset its emissions.
  • 5
    This is compounded by the fact that Canada classifies removals from mature forests as human-caused.
  • 6
    Agricultural land is already under significant pressure from rising global food demand, expanding populations and the need to balance land use with biodiversity conservation and climate mitigation efforts. A 2022 analysis estimated that afforestation and bioenergy production could place an additional 41.9 million people at risk of hunger by 2050 due to higher food prices and displacement of agricultural land
  • 7
    The RCP 2.6 emissions pathway in the IPCC’s Sixth Assessment Report.
  • 8
    Values obtained from Supplementary Table S1 in the report.
  • 9
    Values obtained from Table 6.2: Sectoral mitigation potentials in 2030 and 2035.
  • 10
    This is a rough calculation assuming a direct comparison between land-use footprint in the IPCC technical mitigation potential and the analysis in Deprez et al. (2024) and was calculated as the difference between the IPCC estimates of 15.6 billion metric tonnes and the lower sustainability risk estimate of 3.3 billion tonnes.
  • 11
    The IPCC recommends that these models are interpreted in the context of their assumptions.

Climate change is driving natural systems beyond their limits

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This article is also available in Spanish.

Key points:

  • Emissions of greenhouse gases in the post-industrial era have significantly altered the planet’s climate, resulting in extreme weather anomalies across the globe.  
  • While extreme events such as droughts, storms, heat and unpredictable precipitation are natural phenomena, the increased severity and magnitude with which they are occurring under climate change exacerbates their impacts on humans and natural systems.
  • Changes in climate and land use are making animals’ and plants’ habitats unlivable, forcing them to migrate or adapt, or otherwise become extinct. This has knock-on effects for human livelihoods.
  • Natural systems face pressure from both climate effects, such as heat, and human effects, such as land-use change, with the combination of these stressors intensifying challenges.
  • Environmental changes in one system are triggering reactions in other systems, with cascading effects that threaten the stability of the planet’s climate systems. 
  • Scientists are increasingly worried that climate change is edging natural systems closer to dangerous positive feedback loops that fuel more extreme weather and environmental degradation, in turn accelerating the pace of global warming. 
  • Every increment of warming increases the chance of dangerous positive feedback loops, the effects of which – including the loss of crucial global carbon sinks and weather-modulating ecosystems – are often irreversible.
  • Atmospheric concentrations of greenhouse gases have reached unprecedented levels in recent years, and deforestation and land degradation continue to erode the capacity of the land to absorb carbon dioxide from the atmosphere. 
  • To reduce detrimental warming to humans and nature and meet Paris Agreement targets of limiting warming to 2°C or 1.5°C with little or no ‘overshoot’ – where temperatures temporarily exceed the target before dropping back – “rapid and deep, and in most cases immediate” reductions in greenhouse gas emissions will be needed across all sectors.

Climate change is intensifying weather anomalies

Since the discovery that burning carbon-rich materials such as coal, oil and natural gas can generate heat to power industrial activities, humanity has released billions of tonnes of carbon that had been stored in the Earth for millions of years into the atmosphere. This massive and continuous release of carbon dioxide and other greenhouse gases, including methane, has significantly altered the planet’s climate. Since the onset of the Industrial Revolution, the Earth’s average temperature has risen by approximately 1.2-1.3°C – driven largely by the continuous and unchecked accumulation of these emissions.1The range of 1.2-1.3°C represents a five-year average.

The speed of global warming has ramped up considerably over the last three decades, and particularly since 2015, attributed to increased fossil fuel emissions, deforestation and changes in land use. Despite pledges made to curb emissions in the Paris Agreement, where most countries worldwide agreed to limit “the increase in the global average temperature to well below 2°C above pre-industrial levels” and to pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels” by the end of the century, the last 10 years have been the hottest on record. 2023 is officially the hottest year on record since record-taking began. 

This planetary warming is intensifying weather anomalies across the globe, resulting in more frequent and severe storms, heatwaves and droughts, and unpredictable precipitation patterns. While droughts, storms, heat and extreme precipitation are natural phenomena, the increased severity and magnitude with which they are occurring under climate change exacerbates their impacts on humans and ecosystems (Figure 1). 

Extreme heatwaves are now occurring at almost five times the frequency they were occurring during pre-industrial times and are anticipated to further increase in frequency by 8.6 times at 1.5°C of warming, 13.6 times at 2°C of warming, and 27.4 times at 3°C of warming. Every increment of warming amplifies the climate risks to ecosystems and humans. 

Paris Agreement targets 

The 1.5°C target, endorsed by the Intergovernmental Panel on Climate Change (IPCC), marks a crucial threshold beyond which the impacts of global warming become increasingly severe for both humans and the environment. This target was determined based on the risks posed by increasing temperatures on a range of factors, including food security, extreme weather events, health, biodiversity loss, water supply and economic growth. 

February 2023 to January 2024 marked the first 12-month period in human history where average global temperature rise exceeded 1.5°C. Although breaching the Paris Agreement target would require average annual temperatures to stay above 1.5°C for at least 20 consecutive years, the fact that we are already seeing consecutive months exceed this threshold suggests that we are approaching this critical point.2The point where 1.5°C of warming is breached is measured as the midpoint of the first 20-year period where global average temperatures are 1.5°C higher than the pre-industrial average.

Even though the 1.5°C target has not yet been breached, we are already experiencing the consequences of global warming. Though substantially less risky than higher global warming levels, the target of 1.5°C should not be viewed as a definitive ‘safe’ limit – there is no universally ‘safe’ level of global warming. What is considered an acceptable level of warming will be highly subjective. For example, extreme heat in 2024 alone has had tragic consequences for people and nature: in Saudi Arabia, during the Hajj pilgrimage to Mecca, 1,300 people collapsed and died as temperatures soared in June, while almost 40 monkeys drowned in a well in India in a desperate effort to reach water as lakes have dried up the same month. 

Current policies place us on a trajectory to reach 2.7°C of warming by 2100. The expected impacts would not increase linearly, with certain effects becoming disproportionately severe. For example, the chance of having a major heatwave increases to 30% under 1.5°C of warming, but more than doubles to 80% at 3°C. At local levels, the impacts of a warmer world are also non-linear: as the global temperature reflects an average from across the world, actual temperatures in specific locations vary significantly, from much lower to much higher than the global average. 

This variation means that the impacts of warming are unequally distributed – ​​actual temperatures in specific regions can vary greatly – some places may warm much faster or slower than the global mean. For example, average July temperatures in 2023 for parts of northern and eastern Canada – which experienced record-breaking forest fires that year – were up to 7°C higher than the 30-year average. 

Fig. 1: Risks to land and ocean systems with increasing levels of global warming
Source: Figure SPM.3, IPCC Sixth Assessment Report, 2022. Circles from least to most indicate increasing levels of confidence. Colours from palest to darkest indicate increasing risk. 

Climate and land-use changes are critically altering ecosystems and affecting species in a number of ways, resulting in biodiversity loss (Fig. 1). Estimates suggest that wildlife populations have declined by 69% over the past five decades due to human impacts. Future climate change could cause abrupt and irreversible species loss this century, affecting marine ecosystems as early as 2030 and land ecosystems around mid-century. 

Reduced biodiversity weakens ecosystem resilience to climate impacts and also reduces ecosystem services – i.e. the benefits that humans derive from natural ecosystems – such as food security, climate regulation and carbon sequestration. Though difficult to quantify because of the innate complexity of natural systems and their interactions, ecosystem services worldwide are estimated to be worth USD 150 trillion a year – or twice global GDP in 2021, and at least 1.5 times 2023 GDP.

The relationship between climate and biodiversity is deeply intertwined  

The impacts of climate change on natural systems are complex and interconnected, making them difficult to predict and manage. Ecosystems face pressure from both climate effects, such as heat, and human effects, such as land-use change, with the combination of these stressors intensifying challenges for natural systems. Climate change is driving species to shift their geographic ranges as they seek more suitable habitats in response to changing temperatures, altered precipitation patterns and disruptions to their ecosystems. 

As temperatures rise, marine and land species are moving poleward or to higher elevations to find the conditions they need to survive, or otherwise risk extinction. Shifts in species’ distributions can lead to new interactions between species and their environments, with potential knock-on effects for human livelihoods. 

Marine migrations and mortality: lobsters, sardines, cod and anchovies

For example, climate change-driven increases in ocean temperatures are pushing American lobsters northward along the US coast, disrupting local fishing industries. Warmer waters along the coast of Northwest Africa are driving sardines northwards, presenting a risk to millions of people in the region that rely on these fish for food security. On the west coast of South America, warmer ocean temperatures are shifting anchovy populations, thereby threatening a globally important commercial fish industry. In these situations, fishing pressure under climate change could exacerbate the stress on fish populations that are already struggling to adapt to new environments, potentially leading to overexploitation and further declines in fish stocks. 

For extreme events with a sudden onset, such as heatwaves, some species may not be able to migrate or adapt quickly enough as they are pushed beyond their thermal tolerance limits, i.e. the temperature range within which a species can survive and function. Marine heatwaves in 2014-16 and 2019 in Alaska drastically disrupted Pacific cod populations, resulting in the closing of the fishery – Alaska’s second-largest commercial groundfish fishery – in 2020. 

In the Mediterranean Sea, climate change is increasing the frequency and intensity of marine heatwaves, leading to widespread mass mortality events of marine organisms. From 2015 to 2019, the Mediterranean Sea experienced five consecutive years of mass mortality events, affecting a vast range of marine habitats and species, posing a severe threat to the functioning of its ecosystems. 

Coral bleaching: too hot to recover

One of the most striking examples of climate change-induced mass mortality is warm-water coral reefs, which are increasingly facing mass mortality from human-caused marine heatwaves (Figure 1). Between 2009 and 2018, around 14% of corals from the world’s reefs had been lost, an amount larger than Australia’s coral reefs, largely due to bleaching, where corals expel the symbiotic algae that they depend on for existence in response to high water temperature, ultimately resulting in death if the warm water conditions persist. 

Though corals can recover if water temperatures cool quickly enough, the increasing frequency of  heatwaves due to climate change means that the corals’ windows for recovery between heatwave events are getting smaller, potentially leading to extinction. At 1.5°C of warming, estimates suggest 99% of coral reefs could be lost, with no coral reefs existing at 2°C. 

For humans, this means the loss of critical ecosystem services, such as coastal protection, food resources and recreation. Coral reefs reduce wave energy by up to 97%, safeguarding 5.3 million people and USD 109 billion in GDP per decade. Reef tourism is valued at USD 35.8 billion a year,3In 2017. while reef-associated fisheries are valued at USD 6.8 billion.4In 2011.  

Heat on land: mass mortality of flying-foxes, birds and howler monkeys 

On land, mass mortality events from heatwaves have been recorded in flying-foxes – bats that eat fruits and nectar. Flying-foxes play a crucial role in ecosystems by pollinating plants and dispersing seeds over large distances in their native habitats across South and Southeast Asia, Australia and East Africa. This helps maintain plant biodiversity and regenerate forests. They are also critical pollinators for commercially valuable foods, such as durian fruit. Despite their mobility, flying-foxes  are extremely sensitive to heat stress: during the 2019-2020 summer in Australia – one of the hottest on record, made worse by climate change – at least 72,175 flying-foxes died from heat stress. 

Mass mortality events on land have also been recorded elsewhere: an extreme heat event in South Africa in 2021 killed more than 100 wild birds and bats. Heatwaves in Mexico in 2024 caused the death of over 200 howler monkeys in the wild. Howler monkeys are important seed dispersers, particularly in forests disturbed by humans where they help to restore degraded habitats. 

Drought: mass animal mortality induced by complex, additive effects

Prolonged dry spells are becoming more common in South America: over the 10 years between 2005 and 2015, three once-in-a-century droughts – or megadroughts – occurred in the region. Severe drought in Colombia in 2014 is reported to have caused the mortality of at least 20,000 animals, including wild pigs, deer, crocodiles and tortoises. The interplay of land-use change – particularly deforestation – and human-caused climate change is intensifying the impacts of the drought: deforestation in Brazil and Bolivia has aggravated drying in Colombia by changing the patterns of moisture cycling by forests across the region.  

Declining pollination: a threat to food security

Pollination is a critical ecosystem service for humans, with the annual contribution of pollinators to global agricultural production and food security estimated at more than USD 500 million. Changes in climate are also disrupting the finely tuned relationships between insect pollinators and the plants they pollinate by altering the timing of flowering and pollinator activity. This creates a mismatch that can reduce pollination efficiency, with impacts on food security and prices. 

Bumblebees in Europe and North America are declining due to climate change, among other factors. This decline is threatening essential pollination services and could lead to an ‘extinction vortex’, where the loss of bumblebees negatively impacts the plants they pollinate, further endangering both species. Further studies indicate that bumblebees will continue to face declines with climate change. More widely, a study on 38 globally distributed insects projects that up to two-thirds could become extinct this century. According to the IPCC, three times the number of insects will lose more than half of their climatically suitable ranges at 2°C of warming compared to at 1.5°C. 

Dangerous feedback loops that perpetuate warming 

Environmental changes in one system may trigger reactions in other systems. For example, climate change is increasing the likelihood of wildfires by creating hotter, drier conditions and extending the fire season, all of which make ecosystems more vulnerable to burning (Fig. 2). Forests, which are estimated to cool the earth by 1°C, play a crucial role in global carbon storage and are increasingly threatened by wildfires. 

Climate-induced drying is transforming forests into highly flammable tinderboxes, increasing their vulnerability to wildfires. As prolonged droughts and elevated temperatures reduce soil moisture and dry out vegetation, forests are becoming less efficient at sequestering carbon and more prone to fires. These fires not only devastate vast areas of forest, thereby reducing their ability to absorb carbon, but also release stored carbon back into the atmosphere, further amplifying global warming. This creates a dangerous positive feedback loop, where rising temperatures fuel more extreme weather and environmental degradation, which in turn accelerates the pace of climate change.

Fig. 2: Illustration of a forest fire feedback loop
Source: World Resources Institute, 2020.

If the feedback loop is not stopped, the system could reach a critical threshold where a small change can trigger a significant and potentially irreversible shift in the system’s behavior or state, called a ‘tipping point’. Once a tipping point is reached, the system may undergo rapid changes that are difficult or impossible to reverse, even if the original trigger is reduced or removed (see fig. 3).  

Fig. 3. Visualisation of a tipping point
Source: Rate-induced tipping in natural and human systems, 2023. 

Figure 3 represents a landscape where the trough shows the stable ‘base state’ or natural condition of the system, the ball shows the system’s current state and the vertical red line shows the threshold. If the  ball, which represents the system, is to the left of this threshold, it rolls into the trough and returns to its stable natural state. If the ball rolls over the hill to the right and crosses the threshold, it rolls away towards a new state.

Tipping points can occur either quickly or slowly depending on the system. Fast-onset tipping points happen within years or decades after crossing a critical threshold. For example, the transformation of forest into savanna due to wildfires and drought. Slow-onset tipping points develop over much longer timescales, such as centuries. Here, a system might exceed a critical threshold without immediately transitioning into an alternative stable state, but the change eventually becomes unavoidable over time. An example of a slow-onset tipping point is the thawing of permafrost or ice sheets.

Runaway wildfires in Canada

Though wildfires are natural phenomena, they are becoming larger and more frequent – fires are burning almost double the amount of forest that were burning two decades ago. Canada experienced devastating forest wildfires in both 2023 and 2024, with 2023’s extreme wildfires found to have been made more than twice as likely due to climate change. The 2023 forest fires are believed to have released around 640 million tonnes of carbon, or about the same annual emissions from fossil fuels in a large industrialised nation.

Drought, fire and beetles in the US

A warming climate is causing more tree mortality in the western US from increased fire, drought and insect outbreaks. Warm conditions during the 2012-14 drought in California – aggravated by human-caused warming – not only reduced tree resilience but also increased populations of bark beetles, which infested ponderosa pine trees and increased their mortality by almost 30%. This highlights the intricate interplay between climate and ecosystems and how climate-induced changes can disrupt ecosystem balance and have cascading effects. It is estimated that every 1°C increase in local average temperature increases ponderosa pine mortality by 35-40% due to the additive effects of climate and beetles.   

Fire in the Brazilian Pantanal

Wildfires in 2024 in South America’s Pantanal Wetland – the world’s largest tropical wetland and one of the most biodiverse regions on earth – have burnt more than 13% of the biome. The fires were fuelled by climate change, estimated to have made these fires 40% more intense and 4-5 times more likely. If global warming reaches 2°C, fire conditions like these in the region will become twice as likely. In addition to threatening species survival and human livelihoods, the cascading effects of disruptions such as these threaten the stability of the planet’s climate systems.

Deforestation, fire and drought in the Amazon

Scientists are increasingly worried that the effects of drought, wildfires and deforestation in the Amazon – the earth’s largest rainforest – may cause it to enter a dangerous positive feedback loop, potentially leading to a sudden tipping point, transforming into an alternative state such as a savanna. 

This change would result in the irreversible loss of a major carbon sink – as once a certain level of damage is done, the forest will not be able to regenerate and recover – potentially releasing up to 90 billion tonnes of carbon dioxide, more than double annual emissions from fossil fuels. 

In some parts of the Amazon, particularly in the eastern region where deforestation rates are highest, the forest is already releasing more carbon than it can absorb. An Amazon tipping point would also mean the loss of a critical modulator of regional climate, with every country in South America, apart from Chile which is shielded by the Andes, benefitting from the moisture generated by the Amazon.  

Alarmingly, the Amazon has already lost up to 15% to 17% of its forest area. Scientists estimate that the Amazon could reach a tipping point once 20-25% of native forest is lost. Other estimates suggest that a tipping point could be reached by 2050, corroborated by another analysis that suggests that the region could experience severe ecological disruption by mid-century, compromising the capacity of the forest to store carbon.

Glacier melt in the Andes 

Glaciers gradually form as snow accumulates and compacts over centuries. They typically grow during winter and melt in warmer seasons, with the meltwater providing a water source that is replenished during glacier growth. However, rising global temperatures are causing glaciers to shrink faster than they can regenerate. As glaciers retreat, the meltwater volume increases until reaching a tipping point, beyond which it declines until it stops as the glacier eventually disappears. 

Tropical glaciers in the Peruvian Andes are highly sensitive to climate change. Between 2000 and 2016, the area covered by glaciers in Peruvian Andes shrank by almost a third, attributed to a combination of climate change and the intense El Niño of 2015/16.5El Niño events are becoming more intense as a result of climate change. Meltwater from glaciers is a critical resource for drinking, irrigation and hydroelectric power and therefore has wide-ranging consequences for both urban and rural populations in the region. 

Permafrost and ice sheet melt in the Arctic, Greenland and the Antarctic

The Arctic is warming almost four times faster than the global average. This is leading to the melting of permafrost – a layer of soil rich in organic materials that has been frozen for many years – potentially causing a dangerous positive feedback loop. As permafrost thaws, microbial activity causes the significant release of greenhouse gases, including carbon dioxide and methane, which have been trapped in the frozen ground for millennia. 

The release of these gases contributes to further warming of the atmosphere, which in turn accelerates the thawing of permafrost. This cycle can lead to increasingly rapid permafrost degradation, amplifying global warming and exacerbating climate impacts worldwide – it is estimated that Arctic permafrost holds up to 1,600 billion tonnes of carbon, about twice the amount of carbon present in the atmosphere today. 

Of particular concern is the release of methane from permafrost, which is a potent greenhouse gas with a global warming potential that is 28-36 times higher than carbon dioxide.6This refers to the amount of heat a greenhouse gas traps relative to carbon dioxide, evaluated over a 100-year period in this example. At just 1.5°C of warming, there is high confidence that the risk of permafrost degradation is ‘high’, increasing to ‘very high’ at just over 2.0°C of warming. Permafrost thaw also comes with an additional risk: it releases pathogens that may pose significant health risks to humans and animals, as was the case with an outbreak of anthrax disease studied in 2020. 

The Arctic is also experiencing a reduction in sea ice extent due to rising global temperatures. This loss of sea ice contributes to a dangerous feedback loop: ice reflects sunlight, but as it melts, the darker ocean absorbs more heat, thereby accelerating warming. Scientists estimate that an Arctic sea ice tipping point could be imminent – at between 1°C and 3°C of global warming. Similar estimates have been made for the Greenland ice sheet and West Antarctic ice sheet. 

The collapse of these ice sheets will increase sea levels globally, devastating coastal areas in the absence of concerted adaptation efforts. With anticipated warming this century, the ice sheets are expected to continue melting, but as these sheets grow much slower than they melt, this could result in a lag response – meaning they will continue to melt even once temperatures stabilise. Their melting may not be reversible this century and we are likely to still be locked into several meters of sea level rise.

The collapse of a critical Atlantic Ocean current 

Another example of a crucial tipping point is the collapse of the Atlantic Meridional Overturning Circulation (AMOC) – a critical ocean current system that modulates global climate by transporting heat, freshwater and carbon. If the AMOC slows down and collapses, it would result in an irreversible change to global climate, including disrupting rainfall patterns in the Amazon, with catastrophic consequences for global carbon cycling as well as agricultural production and food security from decreased ocean productivity and changes in weather patterns. According to climate scientist Tim Lenton, a collapse would cause changes to the earth’s climate that would be “so abrupt and severe that they would be near impossible to adapt to in some locations”. 

The AMOC has weakened since industrial times – with a significant contribution from human-caused warming – and is likely to continue weakening this century. However, it is debated how soon a complete collapse could occur. One analysis estimates that it is concerningly close – by 2057 – with another analysis also suggesting that the AMOC is on course for reaching a tipping point in a century’s time or potentially even sooner.  

Overshooting Paris Agreement targets

The term ‘temperature overshoot’ is used by the IPCC to describe scenarios where global warming temporarily surpasses a target level, typically 1.5°C to 2°C, before eventually declining back to that level. Temperature overshoot scenarios are common in climate models: according to the IPCC’s “Global Warming of 1.5°C” report, 90% of the pathways that aim to limit warming to 1.5°C by 2100 involve a period of overshoot. 

Scientists warn that temperature overshoot poses a risk to species through prolonged exposure to temperatures beyond their historical tolerance limits – that is, the environmental limits within which they have adapted over many years. This extended exposure can lead to increased stress, reduced resilience, and, in some cases, irreversible damage to ecosystems and extinction of species – even once global temperatures begin to decline back to a target temperature following a peak in warming during an overshoot. The risks are especially high for tropical ecosystems, such as the Amazon and the Pantanal, and tropical coral reefs, where species are particularly sensitive to temperature changes. 

Achieving a 1.5°C limit with minimal or no overshoot requires rapid and significant reductions in emissions, with limited carbon dioxide removal (CDR), such as reforestation or bioenergy with carbon capture and storage (BECCS). On the contrary, pathways that delay emissions reductions are more likely to overshoot the target, necessitating greater reliance on large-scale CDR to lower global temperatures by the century’s end – which comes with various risks and uncertainties.  

The IPCC warns that climate-related risks are higher if global warming overshoots 1.5°C compared to if warming gradually stabilises at 1.5°C. The longer emissions cuts are postponed, the more we risk exposing ecosystems and human populations to severe climate impacts over the coming decades, sometimes with irreversible consequences.

Solutions are available to limit catastrophic warming 

Limiting detrimental warming to humans and nature to meet Paris Agreement targets of keeping warming to 1.5°C with little or no overshoot, or to 2°C, requires “rapid and deep, and in most cases immediate” reductions in greenhouse gas emissions in all sectors. 

Energy-related carbon dioxide emissions reached unprecedented levels in 2023, and atmospheric carbon dioxide concentrations in recent years were at their highest in 4.5 million years. Methane concentrations in the atmosphere have been rising “dangerously fast” since around 2007, and have reached record levels in recent years. As the earth continues to warm, the ocean and land will become less effective sinks for slowing the rate of increase of greenhouse gases in the atmosphere, undermining the planet’s natural ability to mitigate climate impacts.

Deforestation from land-use change – primarily from agriculture – and rising temperatures means that forests are losing their capacity to sequester carbon – an ecosystem service valued at up to USD 135 trillion. If uncurtailed, deforestation and land degradation will continue to release carbon dioxide and erode the capacity of the land to absorb carbon dioxide from the atmosphere. At the same time, land-use change, including deforestation, accounts for around 10% of global greenhouse gas emissions,7In 2010. making it a significant contributor to climate change. 

The most efficient and affordable way to cut emissions is by reducing dependence on fossil fuels and transitioning to renewable electricity. To meet the 1.5°C target, the IPCC recommends that coal usage must be eliminated, and oil and gas consumption reduced by 60% and 70%, respectively, by 2050.8Compared to 2019 values. Increased electrification with nearly all power from zero or low-carbon sources is essential. 

Reducing emissions from methane, a short-lived gas with a high global warming potential, is one of the quickest and most effective ways to slow global warming. Addressing methane sources such as pipeline leaks and abandoned oil and gas wells, and introducing technologies for mitigating livestock methane, could cut human-caused methane emissions by up to 45% by 2030. This could prevent nearly 0.3°C of warming by the 2040s, leading to significant health benefits and savings. To keep warming below 1.5°C, the IPCC recommends a 34% reduction in methane by 2030. Existing technology can reduce methane emissions from fossil fuel operations – which contribute around 40% of human-caused methane – by 70%, according to the International Energy Agency (IEA). 

If countries and companies do not reduce their fossil fuel production, they risk increasing the costs of achieving a just and equitable energy transition as well as diminishing returns on investments and USD 1.4 trillion in stranded assets. 

Renewable power is becoming more and more accessible: costs from wind and solar have been falling since 2010, reaching record-low levels in recent years and making them increasingly competitive with fossil fuels. In 2022, 85% of added global utility-scale wind and solar capacity was more affordable than fossil fuel alternatives. In 2023, additions of renewable energy – particularly solar photovoltaic – grew at the fastest rate in the past two decades, by almost 50% compared to 2022. To meet the 1.5°C target, rapid renewables deployment of around 1,000 GW per year until 2030 will be necessary. 

Restoring degraded lands, preventing further deforestation and planting forests can significantly enhance carbon sequestration, improve resilience to climate impacts and help stabilise the global climate​. For example, forests managed and protected by Indigenous People in the Amazon between 2001 and 2021 removed 340 million tonnes of carbon dioxide from the atmosphere each year – more than the fossil fuel emissions of the UK in 2022. Forest restoration and protection are recognised by the IPCC as key to limiting global warming to 1.5ºC or well below 2ºC and come with various co-benefits, including supporting biodiversity, improving air and water quality, flood control and reversal of land degradation, if managed properly.

  • 1
    The range of 1.2-1.3°C represents a five-year average.
  • 2
    The point where 1.5°C of warming is breached is measured as the midpoint of the first 20-year period where global average temperatures are 1.5°C higher than the pre-industrial average.
  • 3
    In 2017.
  • 4
    In 2011.
  • 5
    El Niño events are becoming more intense as a result of climate change.
  • 6
    This refers to the amount of heat a greenhouse gas traps relative to carbon dioxide, evaluated over a 100-year period in this example.
  • 7
    In 2010.
  • 8
    Compared to 2019 values.

Finding economic value in nature beyond carbon

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Key points:

  • Rates of biodiversity loss and nature degradation are alarming, with regions around the world at risk of long-term economic instability, worsened climate change and weakened natural systems.
  • Though hard to quantify because of the complexity of natural systems, ecosystem services – the benefits humans receive from nature, such as food and climate regulation – are estimated to be worth more than USD 150 trillion a year, or around one and a half times global GDP. 
  • Biodiversity loss is currently costing the global economy more than USD 5 trillion a year. USD 5 trillion is roughly the same amount it would cost Europe to transition to renewable energy by 2050.
  • Economies around the world are highly dependent on nature. China, the EU and the US have the highest absolute GDP exposed to nature loss – a combined USD 7.2 trillion.
  • Conservative estimates suggest that nature loss could cost the global economy at least USD 479 billion per year by 2050.
  • The negative consequences or costs associated with the destruction of nature can be greater than any economic benefits or value added from activities causing the destruction.  
  • The destruction of nature in one region can ripple across natural systems, with far-reaching consequences beyond local borders. For example, deforestation causes droughts and elevates temperatures far beyond the site of deforestation, threatening food security and economies in other regions.  
  • Nature adds ‘free’ value to society by providing essential ecosystem services that support life and economic activity without direct costs. For example, conserving  natural habitats near farms boosts production.
  • Fortunately, estimates suggest that conserving biodiversity and ecosystems is much more affordable than destroying them.
  • Restoring and preserving biodiversity is substantially less expensive than building a net-zero emissions energy system – the required annual investment in biodiversity is only 15% of that needed for energy system transition.
  • The funding gap for biodiversity conservation is approximately USD 830 billion per year, comparable to the size of the global tobacco market. 

Human societies are fundamentally dependent on nature 

Nature provides a host of valuable ‘ecosystem services’ – the benefits humans receive from natural ecosystems, such as food, medicine, resources, clean air, climate regulation, climate change mitigation and disease control. These services are essential for sustaining life. 

Biodiversity – the variety of species, genes and ecosystems on earth – is key to supporting nature’s ecosystem services and the value they bring. Biodiversity helps maintain ecosystem balance by supporting species interactions that regulate nutrient cycling, water filtration and climate regulation. It ensures resilience to environmental changes, since diverse ecosystems are better able to recover from disturbances such as extreme weather events. Biodiversity is also important for preserving the genetic diversity that is crucial for the adaptation and evolution of species.

Rates of biodiversity loss and nature degradation are alarming – 50% of natural ecosystems are in decline, over 85% of wetlands are lost, and 25% of species are at risk of extinction. More than three-quarters of essential ecosystem services have decreased over the past 50 years. Additionally, there has been a significant decline in per person ‘natural capital’ – the world’s stocks of natural assets. The stock of natural capital per person declined by almost 40% between 1992 and 2014, while produced capital per person doubled over the same period.

Nature-related risks like deforestation, habitat destruction and resource depletion can lead to long-term economic instability, worsened climate change and weakened natural systems resilience. For example, the diversion of rivers for cotton farming has depleted the Aral Sea in Central Asia, causing an economic crisis as well as increased local and regional temperature extremes due to the impact on the sea’s climate regulating function. 

Nature-related risks are interconnected, meaning that a disruption in one area can amplify risks in other areas. For example, moisture from the Amazon helps generate rainfall in the region and in surrounding areas. Deforestation reduces this function, causing drought in neighbouring regions and impacting agriculture, water availability and overall climate stability across most of South America.
Five human-caused drivers are responsible for 90% of nature loss over the last 50 years: land- and sea-use change, climate change, natural resource use and exploitation, pollution and alien invasive species.

It pays to protect nature

Financial value of nature 

Though hard to quantify because of the complexity of natural systems, ecosystem services globally are estimated to be valued at more than USD 150 trillion a year, or at least one and a half times global GDP in 2023. The ocean economy alone has a value of up to USD 3 trillion a year, or 3% of global GDP. 

The knock-on effects of current biodiversity loss are costing the global economy more than USD 5 trillion a year. USD 5 trillion is roughly the same amount of investment needed for Europe to transition to renewable energy by 2050. Conservative estimates suggest that a collapse of essential ecosystem services, including pollination, marine fisheries and timber provision in native forests, could result in annual losses to global GDP of USD 2.7 trillion by 2030.1This model includes various tipping points, which are changes in an ecosystem that push it into an entirely different state, such as the transition of forests into savanna due to land degradation and climate change, with potentially catastrophic changes for global climate regulation. The model baseline is a scenario where these services do not collapse. Similarly, biodiversity loss is believed to be costing the global economy 10% of its output every year.   

The global economic costs of eroded ecosystem services between 1997 and 2011 alone resulted in up to USD 20 trillion in annual losses to the value of these services due to land-use change, and as much as USD 11 trillion in losses due to land degradation. 

A World Economic Forum (WEF) analysis suggests that USD 44 trillion of economic value generation – just under half the GDP of the world – is moderately or highly dependent on nature and its services and is therefore highly vulnerable to nature loss. Construction, agriculture, and food and beverages are the three largest sectors that are highly dependent on nature, the report said. These sectors generate a total of USD 8 trillion in gross value added (GVA) – about twice the size of the German economy.

Analysis of industry-wide GVA at national or regional levels reveals the extent to which economies depend on nature. In some of the world’s fastest-growing economies, such as India and Indonesia, around one-third of GDP is linked to nature-dependent sectors, while Africa generates 23% of its GDP from these sectors. Globally, larger economies including China, the EU and the US have the highest absolute GDP exposure to nature loss – a combined USD 7.2 trillion.

Cost of nature destruction exceeds value of exploiting it

The negative consequences or costs associated with the destruction of nature are in many cases greater than any economic benefits or value added from the activities causing the destruction. For example, deforestation for palm oil production was a key driver of fires in Indonesia in 2015, which on some days released more carbon emissions than the entire US economy. These fires cost the economy USD 16 billion – more than the value added from Indonesia’s palm oil exports in 2014 (USD 8 billion), and more than the entire value of the country’s palm oil production in 2014 (USD 12 billion). 

In Europe, fertiliser runoff is one of the most pressing environmental challenges, with nitrogen pollution from agricultural runoff estimated to cost the EU between EUR 70 billion and EUR 320 billion annually. This is more than double the estimated value that fertilisers add to EU farm income.      

Commodity supply and demand can trigger different environmental impacts in different regions, where extraction might lead to deforestation in one area while consumption worsens pollution in another. In the Netherlands, much of the feed for intensive livestock systems comes from soy, predominantly sourced from Brazil, including from regions linked to deforestation. 

Demand for soy puts immense pressure on the Amazon’s ecosystems, driving deforestation, which leads to biodiversity loss and a reduction in the forest’s ability to capture and store carbon. This not only disrupts local ecosystems but has global consequences, as the loss of the carbon-sequestering capacity of forests accelerates climate change, while the degradation of biodiversity undermines global ecosystem stability. The environmental and health impacts of livestock farming in the Netherlands are estimated to cost EUR 9 billion a year – making the damage by the sector three times higher than its added value. This estimate does not account for environmental impacts outside of the Netherlands.

Costs of inaction

Highly conservative estimates suggest that a reduction in six essential ecosystem services – namely pollination, coastal protection, water yield, timber, fisheries and carbon sequestration – could cost the global economy at least USD 479 billion per year by 2050, or cumulatively almost USD 10 trillion,2Between 2011 and 2050. with a 0.67% drop in global GDP every year.3This is under a ‘Business-as-Usual’ scenario, which is a high-emissions scenario aligned with the RCP8.5 pathway used in the IPCC’s Sixth Assessment Report. The economic model does not include impacts from tipping points, such as the collapse of rainforests or pollination. Land degradation, desertification and drought are anticipated to cost the global economy USD 23 trillion by 2050. 

Global GDP could contract by USD 2.7 trillion as early as 2030 if the timber, pollination and fisheries industries partially collapse as a result of environmental destruction.4As the analysis only considered a narrow set of risks, the authors of the report warn that this estimate should be viewed as a lower bound. Credit rating firm Moody’s also identifies eight sectors, including protein and agriculture, with ‘high’ or ‘very high’ inherent exposure to natural capital and with almost USD 1.6 trillion in rated debt. Increasing environmental pressures will erode the capacity of these sectors to pay their debts.

Companies involved in nature destruction face increasing financial risks. For instance, a palm oil company was fined USD 18.5 million for fires that destroyed forested land on its concession in Borneo in 2015. Similarly, the world’s largest meat company JBS received USD 7.7 million in fines in 2017 for sourcing cattle from deforested areas in the Amazon. 

New regulations and shifts in demand as societies respond to climate change could mean that 40 of the world’s largest food and agricultural firms, together worth more than USD 2 trillion, lose up to 26% of their value by 2030. This equates to a loss to financial institutions connected to these firms of USD 150 billion – comparable to the value of financial institution losses following the 2008 financial crisis. A 2023 report found that the total financial impact of deforestation for 1,043 companies that disclosed their deforestation risks in 2022 is nearly USD 80 billion, emphasising the need for urgent and effective management of deforestation risks.

Nature has value beyond carbon

Natural systems, such as forests, are often valued primarily for their role in carbon capture and storage – global forests are estimated to be worth at least USD 150 trillion, almost twice the value of global stock markets and over 10 times the worth of all the gold on Earth. While carbon sequestration accounts for a substantial portion of this value, forests are invaluable beyond this.

Global human health is intricately tied to tropical rainforests, which host an immense variety of plant species, many with medicinal properties. Between the 1940s and 2006, almost half of anti-cancer pharmaceutical drugs originated from products of natural origin. 

It is estimated that every new pharmaceutical drug discovered in tropical forests is worth USD 194 million to a pharmaceutical company and USD 927 million to society as a whole. With almost 90% of pharmaceutical drugs originating from tropical forests still yet to be discovered, the total value to society could be as much as USD 303 billion.5Values have been adjusted from 1995 values to 2024 values based on the Consumer Price Index and have not taken into account any industry-specific changes such as changes in market dynamics or production costs.

In the cosmetics sector, the supply of shea butter, used in various topical products, comes from a tree that is threatened by deforestation and pollinator loss.

The value of nature extends beyond the extraction of goods. Mangrove forests, which are valued for their vast carbon sequestration ability, also offer significant economic benefits from flood protection, including for the US, China, India and Mexico. It is estimated that mangroves reduce damage to property from floods by more than USD 65 billion per year and protect more than 15 million people.

The costs of nature destruction transcend borders 

The destruction of nature in one region can ripple across natural systems, with far-reaching consequences beyond local borders. Deforestation in the Amazon, Congo and Southeast Asia has been linked to significant reductions in both local and regional rainfall. This can negatively impact agriculture and hydropower generation, posing threats to food security and energy generation beyond local borders.  

Deforestation in Brazil and Bolivia has altered regional rainfall patterns, exacerbating droughts in neighbouring regions. In Colombia, the 2015-2016 megadrought was intensified by these disruptions in moisture recycling. This drought caused a national energy crisis as hydropower – responsible for over 70% of Colombia’s energy – became unreliable due to plummeting river water levels. As a result, energy prices soared nearly tenfold, showcasing how environmental damage in one country can exacerbate economic consequences in another. 

The impacts of deforestation go beyond drought. In Southeast Asia, logging and the conversion of forests to palm oil plantations causes soil erosion and results in increased soil sediment in rivers. This sediment is carried downstream and is eventually released into the ocean where it settles on coral reefs, threatening their survival. An estimated 41% of coral reefs globally are impacted by sediment export. 

Coral reefs provide a wealth of ecosystem services, such as coastal protection, food and recreation. By reducing wave energy by up to 97%, they protect up to 5.3 million people on coastlines and USD 109 billion in GDP per decade from flooding and erosion impacts. Coral reefs are an important food source, with global reef-associated fisheries valued at USD 6.8 billion.6 In 2010. Additionally, coral reef tourism is valued at USD 36 billion a year, which is more than 9% of total coastal tourism value in the world’s coral reef countries. 

Forests keep people and the atmosphere cool both locally and regionally by providing shade and releasing water vapour, acting as a natural air conditioner and alleviating heat illness. In the Amazon, deforestation can increase temperatures by up to 4.4°C7Note that absolute temperature change can be expressed in Kelvin (K). A change of 1°C is equal to a change of 1 K. as far as 100 km away. Similar estimates have been made for other forested regions around the world. 

Pollution, such as fertiliser and animal waste runoff from unsustainable farming, can have widespread impacts on nature. Runoff from agricultural fields flows into water bodies, leading to excessive nutrient levels, which depletes oxygen in water and harms aquatic life. The Gulf of Mexico’s dead zone – an area of low to no oxygen that can kill marine life – occurs every summer and is mostly caused by nutrient runoff from excessive fertiliser application and livestock on Midwestern US farms, carried to the gulf via the Mississippi River and its tributaries. In August 2024, the dead zone reached approximately 6,705 square miles – an area almost the size of Kuwait – potentially making 4 million acres of habitat unavailable to marine species. 

The yearly costs of the dead zone to fisheries and the marine environment were estimated at up to USD 2.4 billion between 1980 and 2017. Studies have found that the dead zone reduces the size of large shrimps relative to small shrimps, with prices for large shrimps driven up as a consequence, impacting consumers, fishers and seafood markets.

Pollinators ensure our food security 

The agriculture and food and beverage sectors are highly dependent on pollination – a critical ecosystem service of immense economic value that is essential for human well-being through its impact on agricultural production and food security. Pollinators impact about 35% of global crop production by volume, with 87 out of 115 major crops worldwide depending on pollination by animals, such as insects, birds and bats, to some extent. The contribution of pollinators to global agricultural production and food security is estimated at USD 235 billion to USD 577 billion annually. In the UK alone, the value of pollination services from nature is GBP 430 million.8In 2011.

Pollinators are facing a significant threat from habitat loss, pesticide use and land-use changes. More than 40% of insect pollinators worldwide are facing extinction. In the short-term, the costs of a ‘pollinator collapse’ are valued at a mid-point range of USD 1 trillion or around 1-2% of global GDP. 

Native bumblebees in North America are critical pollinators of blueberries. The value of fresh cultivated and wild blueberry exports from the US in 2023 exceeded USD 127 million, with key export markets in Canada, Taiwan, Japan and South Korea. Yet bumblebees are in decline in North America due to habitat loss, pesticide use and climate change, posing a threat to blueberry production.

Pollinator loss is anticipated to continue on an upward trend in the future, with projections indicating that pollinator decline could cause annual crop production losses of more than USD 50 million for the US, around USD 125 million for Brazil, and around USD 225 million for China by 2050.

Nature adds ‘free’ value 

Nature adds ‘free’ value to society by providing essential ecosystem services that support life and economic activity without direct costs. These services are often overlooked in economic calculations, yet they are fundamental to human well-being and environmental sustainability. The destruction of these natural systems can lead to significant financial costs in the long run as humans are forced to replace or mitigate these services.

In Northern California, wild bee species were found to significantly increase tomato production both in terms of size and numbers. Tomatoes are able to self-pollinate, meaning they don’t rely on pollinators to produce fruit, but this example demonstrates the added value from pollination services in nature. 

In Costa Rica, pollinators from forests increased coffee yields by 20% within 1 km of forests and improved coffee quality by reducing poor-quality berries by 27%. The study estimated that pollination services from two forest patches generated around USD 62,000 per year for a single coffee farm, representing approximately 7% of its total income. For both the coffee and tomato examples, simply being in close proximity to forested or natural habitats benefitted production on farms.

The natural flood control function of wetlands offers another example. During Hurricane Sandy in 2012, which devastated the Caribbean and east coast of the US, wetlands are estimated to have saved more than USD 625 million in avoided flood damage.

Solutions and distractions

Conserving biodiversity and ecosystems is estimated to be much more affordable than destroying them. By 2030, an estimated USD 996 billion9In 2021 USD. annually will be required to sustainably manage biodiversity and maintain ecosystem integrity. This represents less than 1% (0.7-0.9%) of global GDP in 2023. It is also substantially less than the amount spent annually on subsidies that accelerate the production or use of natural resources or that undermine ecosystems, which are estimated at USD 1.8 trillion to USD 6 trillion – or around 6% of global GDP. Nature-smart policy interventions, which already have demonstrated success and could achieve further impact and value, can substantially reduce the risk of ecosystem services collapse by 2030, with economic gains of up to USD 150 billion.

Protecting and restoring biodiversity is crucial to achieving net-zero goals – it enhances ecosystem resilience, supports agricultural systems and increases carbon sequestration. At the same time, estimates suggest that restoring and preserving biodiversity is substantially less expensive than building a net-zero emissions system – the annual funding needed to protect and preserve biodiversity is only 15% of the investment needed to transition to a net-zero emissions energy system.

Biodiverse ecosystems like forests, wetlands and grasslands store significant amounts of carbon, helping to offset emissions. They also provide critical services such as regulating the water cycle, supporting pollination and improving soil health, all of which are necessary for sustainable agriculture and climate resilience. It is estimated that a transition to deforestation-free operations, entailing a 75% reduction in deforestation rates by 2025 and the restoration of 300 million hectares of forests, could result in an economic gain of USD 895 billion by 2030 through a reduction in annual environmental costs of USD 440 billion.

Closing the funding gap

The funding gap for biodiversity conservation is approximately USD 830 billion per year, comparable to the size of the global tobacco market in 2022. About 73% of the funding is needed to manage productive landscapes and seascapes, with a significant focus on transitioning agriculture to sustainable practices. 

There are various financial mechanisms for closing this funding gap for biodiversity conservation. Public finance presently plays a significant role, with government budgets and tax policies supporting biodiversity projects. It is estimated that 80% of biodiversity financial flows – around USD 133 billion per year10Value is from a 2022 report. – are from domestic and international public finance.

The private sector contributes around USD 29 billion per year to biodiversity through various sustainable debt products. The largest contributor is payments-for-ecosystem services, where financial incentives are given to landowners or resource managers to adopt practices that conserve or enhance ecosystem services that derive value from nature. These schemes contribute around USD 9.8 billion a year. However, they are often vaguely defined and suffer from issues such as payment volatility and high project costs. 

Debt-for-nature swaps allow countries to cancel portions of their foreign debt in exchange for committing to fund local conservation projects. Estimates suggest that as much as a third of the USD 2.2 trillion of developing country debt could be eligible for debt-for-nature swaps. However, the impact of this on debt levels has been very small: between 1987 and 2023, these swaps offset only ​​around 0.11% of debt payments by low- and middle-income countries. Critics also argue that these swaps sometimes commodify nature and could undermine the sovereignty of local communities if not properly managed.Carbon offsets and credits aim to compensate for greenhouse gas emissions and environmental impacts by investing in projects that reduce or remove carbon from the atmosphere, such as reforestation or afforestation. However, they have been criticised for allowing companies to continue emitting carbon while relying on offset projects that may not always deliver long-term or verifiable climate benefits.

  • 1
    This model includes various tipping points, which are changes in an ecosystem that push it into an entirely different state, such as the transition of forests into savanna due to land degradation and climate change, with potentially catastrophic changes for global climate regulation. The model baseline is a scenario where these services do not collapse.
  • 2
    Between 2011 and 2050.
  • 3
    This is under a ‘Business-as-Usual’ scenario, which is a high-emissions scenario aligned with the RCP8.5 pathway used in the IPCC’s Sixth Assessment Report. The economic model does not include impacts from tipping points, such as the collapse of rainforests or pollination.
  • 4
    As the analysis only considered a narrow set of risks, the authors of the report warn that this estimate should be viewed as a lower bound.
  • 5
    Values have been adjusted from 1995 values to 2024 values based on the Consumer Price Index and have not taken into account any industry-specific changes such as changes in market dynamics or production costs.
  • 6
     In 2010.
  • 7
    Note that absolute temperature change can be expressed in Kelvin (K). A change of 1°C is equal to a change of 1 K.
  • 8
    In 2011.
  • 9
    In 2021 USD.
  • 10
    Value is from a 2022 report.

What to expect from La Niña 

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Key points:

  • La Niña is a natural, reoccurring climate phenomenon whereby cold, deep water moves to the ocean surface and cools the central and eastern Pacific Ocean, and warmer water moves to the western Pacific Ocean.
  • There is an 85% chance of a transition from the current El Niño state to neutral conditions between April and June this year, and a 60% chance of La Niña developing by June to August.
  • La Niña strongly influences rainfall and weather patterns in various regions of the world and has been responsible for catastrophic droughts and floods, which have severely threatened agricultural production and food security, and caused major economic losses.
  • La Niña episodes usually last nine to 12 months, but may last for years. The frequency of multi-year La Niña’s has risen in the past several decades, and the longer duration increases risks from weather extremes. The previous La Niña, which lasted from 2020-2023, had devastating consequences for several regions of the world.
  • Human-caused climate change is at least partly responsible for increases in the variability and frequency of extreme La Niña events.
  • Some regional trends that can be associated with La Niña include:
    • Drier than usual conditions in Ethiopia, Somalia, northwestern and eastern Kenya, northeastern Tanzania, southern and southeastern US, southern Brazil, Uruguay, northern Argentina and southern Bolivia, potentially leading to drought and crop failures.
    • Wetter than usual conditions in eastern South Africa, Mozambique, Zimbabwe, Botswana, northern and eastern Australia, southeast Asia, India, northern Brazil, Colombia and Venezuela, with potential for flooding.
    • Increased Atlantic hurricane activity, with potentially severe consequences for the southeast coast of North America.

The El Niño-Southern Oscillation cycle

The El Niño-Southern Oscillation (ENSO) cycle – entailing periodic fluctuations in sea surface temperature and atmospheric pressure over the tropical Pacific Ocean – is a natural, reoccurring climate phenomenon that strongly influences rainfall and weather patterns in various regions of the world. La Niña is the cool phase of the ENSO cycle, while El Niño is the warm phase, with a neutral period following these phases.

During La Niña, trade winds – the east-to-west winds that blow along the earth’s equator – intensify, which causes cold, deep water to move to the ocean surface and cool the central and eastern Pacific Ocean, and warmer water to be pushed to the western Pacific. During El Niño, roughly the opposite happens, with weakened trade winds causing central and eastern Pacific ocean water to warm up.

El Niño and La Niña episodes usually last nine to 12 months, but may last for years. While the transitions among various phases occur irregularly, the cycling between the warm and cool phases takes place every two to seven years and brings about predictable changes to ocean temperatures, wind and rainfall patterns.1A cold phase does not always immediately follow a warm phase, and vice versa. In many cases, a cool phase follows from a cool phase, with a varying number of neutral condition months in between. ENSO events are described as Eastern Pacific (EP) or Central Pacific (CP) events depending on where the maximum warming or cooling is located.2CP events may also be referred to as ENSO ‘Modoki’. Some impacts of EP and CP events differ. For example, CP El Niño events are associated with more severe droughts in Australia than EP events. There has been an increase in the frequency of CP events in the last four decades.

Based on changes in sea surface temperatures and atmospheric conditions in the tropical Pacific, the National Atmospheric and Oceanic Administration is confident that there is an 85% chance of a transition from the current El Niño state to neutral conditions between April and June this year, with a 60% chance of La Niña developing by June to August. Long-range models predict an EP La Niña event this year.

How are La Niña and El Niño predicted?

Scientists use a combination of climate models and observational data, such as sea surface temperature and trade wind strength data from satellites and ocean buoys, to predict the onset of ENSO events several months in advance. Models can forecast La Niña events up to two years’ in advance if the La Niña follows a strong El Niño rather than any other state.3There have been significant improvements in models’ ability to forecast ENSO events, but these models still face some challenges – for example, they generally overestimate La Niña and El NIño strength.

La Niña and El Niño events are characterised as weak to strong based on the sea surface temperature anomaly – the deviation from the average or baseline – with cooling or warming of 1.5°C or more considered strong. Figure 1 shows the values of the Nino-3.4 index – a measurement of sea surface temperatures in the equatorial Pacific Ocean – from 1950 to 2024. The grey dashed line shows when the sea surface temperature anomaly meets the requirement for an El Niño or La Niña event, generally defined as an anomaly of 0.5°C or more. The red dashed line shows strong La Niña and El Niño events. However, multi-year events that do not exceed this threshold can also have severe consequences, leading to increased risks from droughts, floods and weather extremes due to their long duration – as observed with the 2020-2023 ‘triple-dip’ La Niña. The grey solid line is the global land-ocean temperature index and shows the change in the global surface temperature from 1950 to 2023.

Fig. 1: Sea surface temperature anomalies in the equatorial Pacific and global land-ocean temperature index from 1950-2024
Data source for Niño-3.4 index: US National Weather Service. Data are three-month running averages with a centered baseline. Data source for global land-ocean temperature index: NASA’s Goddard Institute for Space Studies. Values are annual means in reference to a 1951 to 1980 baseline.

By forecasting when El Niño or La Niña will occur, better predictions can be made about possible extreme weather events, helping people to prepare for and mitigate against potential damage associated with these events.

Multi-year La Niña’s are becoming more common

The frequency of multi-year La Niña’s has increased – five of the 10 multi-year La Niña’s over the last 100 years happened in the last 25 years. Multi-year La Niña events have longer-lasting impacts compared to single-year events, such as prolonged above-average rainfall over Australia, Indonesia, tropical South America and southern Africa, and below-average rainfall over the southern United States, Equatorial Africa, India and southeast China.

A study found that multi-year La Niña events are more likely to follow a ‘super El Niño’, which is a particularly strong El Niño – such as the current El Niño, or a CP El Niño. The previous ‘triple-dip’ La Niña event – which lasted from 2020 to 2023 – was a scientific anomaly because it did not match the conventional scientific theories of how prolonged La Nina events develop. Experts reported that it was one of the strongest La Niña events in the past half century. The impacts of this triple-dip La Niña were devastating and included severe flooding in northern Australia, extreme drought in the Horn of Africa – creating one of the worst food security crises in the region for decades, widespread drought in the southwest US, record-breaking hurricane activity, one of the worst droughts on record in South America and heavy rainfall and flooding in Pakistan and northwestern India, with around 15% of the population of Pakistan negatively impacted by the rainfall.4Climate is complex and influenced by multiple processes. For instance, the extreme rainfall in Pakistan was also attributed to human-caused climate change.

La Niña and the Indian Ocean Dipole

The Indian Ocean Dipole (IOD), which is thought of as the Indian Ocean counterpart of El Niño and La Niña, refers to sea surface temperature anomalies in the Indian Ocean that show a ‘dipole pattern’. When the western Indian Ocean is cooler than usual and the eastern Indian Ocean is warmer than usual, this is referred to as a negative IOD. When the eastern Indian Ocean is cooler and the western Indian Ocean is warmer than usual, this is referred to as a positive IOD. Though independent of La Niña, the IOD is frequently triggered by ENSO events, with negative IOD events typically accompanying La Niña events. Negative IOD events have been linked to extreme rainfall in Indonesia and Australia, and drought in East Africa. Stronger negative IOD events have also been found to make La Niña stronger, and CP La Niña events are also typically linked to stronger IOD events. However, the relationship between ENSO and the IOD is complex due to the diversity and substantial variation in regional feedbacks of ENSO.

Influence of human-caused warming

While ENSO events are natural phenomena, they are occurring against a background state of a warming world, which likely influences their characteristics and impacts. Some changes in ENSO characteristics have been observed over the last few decades, including an increase in the frequency of extreme events and an increase in the variability of events. Similarly, one analysis projects that extremely positive IOD events – linked to drought and wildfires in Indonesia and Australia and flooding in East Africa – will become almost three times more frequent in the 21st century due to climate change. As ENSO is naturally a highly variable phenomenon, determining with certainty whether its characteristics are changing as a result of human-caused climate change is complex – especially as sea surface temperature records have only been available since the 1950s. However, the scientific consensus is that human-caused climate change is at least partly responsible for changes in ENSO variability. Climate change may also be making it less easy to predict extreme El Niño and La Niña events, making it more difficult for people to prepare for potential negative impacts.

Cooler conditions under La Niña do not offset global warming

Though La Niña does cause a decrease of around one tenth of a degree Celcius in the earth’s average surface temperature, this cooling is temporary and is only a fraction of the total average warming of the earth by human-produced greenhouse gases – since industrial times the earth’s average temperature has risen about 1.36°C. To put this number into context, average global temperatures during recent La Niña years have been higher than the average temperatures during El Niño years in past decades, highlighting how much the planet has warmed over the last century (Figure 1). In fact, recent La Niña years have been in the top 10 hottest years ever. Despite the decreased average global temperatures under the upcoming La Niña, 2024 will still likely be one of the top five hottest years on record.

Potential regional impacts of La Niña

As weather patterns around the world are influenced by multiple climate drivers, experts warn against concluding what the impacts of an event will be based on one climate driver alone. However, as La Niña brings about predictable changes to ocean temperatures, wind and rainfall patterns, some general trends can be anticipated (Figure 2).

Fig. 2: Regional impacts of La Niña on rainfall and temperature
Source: National Oceanic and Atmospheric Administration, 2016.
Africa

La Niña is typically associated with drier conditions over December-January in East Africa, including in Ethiopia, Somalia, northwestern and eastern Kenya, and northeastern Tanzania, with implications for crops harvested in February and March and negative effects on livestock. In South Sudan, above-average rainfall could be expected, which might increase crop yields or cause flooding.

La Niña is associated with above-average summer rainfall in eastern South Africa, Mozambique, Zimbabwe and Botswana. In terms of agricultural productivity, South Africa tends to see higher yields of maize, sorghum and wheat, whereas Zimbabwe tends to experience increased maize and soybean yields.

Oceania

In Australia, CP El Niño events tend to bring above-average rainfall to the northern and eastern regions and is linked to severe flooding.

North America

The increase in cold water in the Pacific during La Niña pushes the polar jet stream – a fast air current in the polar region of the Northern Hemisphere – northwards, which tends to cause drier winter and spring conditions in the southern and southeastern US and heavy rains and stormy weather in Alaska, western and central Canada, and the northern US.

Generally, the effects of La Niña in the northern hemisphere are most felt during winter, as it brings colder and wetter winters. There is also an increase in the frequency and strength of Atlantic hurricanes.

The arrival of La Niña around September could benefit maize production in the corn belt of the US but could also reduce water levels in Midwest rivers, with implications for grazing pastures.

Asia

Southeast Asia, including Indonesia, Malaysia and the Philippines, experiences above-average rainfall during CP La Niña events, potentially causing severe flooding. However, rice and palm oil production in the region could be boosted. Due to increased rainfall and cooler conditions, La Niña tends to have a net positive impact on grain yields in China.

In India, La Niña will likely cause above-average monsoon rainfall from July to September and may result in decreased production of pulses, sugarcane and wheat in the Indo-Gangetic Plains, but could increase rice production.

South America

Southern Brazil, Uruguay, northern Argentina and southern Bolivia tend to experience below-average rainfall, potentially leading to drought. Crops such as soybean and maize could be negatively impacted. Northern Brazil, Colombia, Venezuela, and parts of Ecuador and Peru typically experience wetter conditions, with potential for flooding.

Unpacking 2023’s unprecedented heat  

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Key Points:

  • Scientists predict that 2023 will be the hottest year to date, with record-high temperatures observed on land and in the sea.
  • June, July, August, September and October this year were the hottest months since records began in the mid-1800s.
  • These temperature extremes are occurring against a backdrop of a planet that has already warmed to unprecedented levels. Every fraction of a degree of warming at the global level increases the odds of additional and often extreme climate impacts, such as heatwaves and severe rainfall.
  • The long-term build-up of greenhouse gases in the atmosphere from burning fossil fuels is the main factor driving increases in earth’s temperature.
  • The speed at which the earth is warming is accelerating at unprecedented levels, and record high greenhouse gas emissions are primarily to blame.
  • Other natural and human-caused factors are acting on top of a high baseline global temperature, edging us towards record-breaking heat at increasingly fast rates as the warming trajectory of the planet continues upwards. Those factors include:
    • A developing El Niño
    • Natural and human-caused variability in Atlantic sea surface temperatures
    • An unusual volcanic eruption
    • Reduced Saharan dust and particulate emissions
    • Reduced sulphur emissions from shipping fuels
    • Record low sea ice levels
    • The 11-year solar cycle
  • Overshooting the Paris Agreement goal of limiting warming to 1.5°C – even temporarily – could have devastating impacts by catalysing large and often irreversible changes to climate systems.
  • At current emissions rates, we may only have six years left until we blow our remaining carbon budget to keep warming below 1.5°C.
  • The impacts of climate change will only worsen until we stop putting more greenhouse gases into the atmosphere than can be removed by the planet.

Temperature extremes in a warming world

Record heat in 2023

June, July, August, September and October this year were unambiguously the hottest months since records began in the mid-1800s, according to data from tens of thousands of meteorological stations across the world.1Scientists are confident that this is the warmest decade in the last 125,000 years. Scientists are now confident that 2023 will be the hottest year on record to date, despite initial predictions that it could be the fourth-hottest year.

September’s heat was particularly unusual, with the highest temperature anomaly – an indication of how divergent temperatures are from the long-term average – ever recorded for any month. One climate scientist described this unprecedented 0.5°C anomaly, which made September around 1.8°C hotter than pre-industrial levels, as “absolutely gobsmackingly bananas”.2Depending on the dataset used, the level of warming may be 1.7°C or 1.8°C. The impacts of this year’s heat were felt across the world: Africa, Europe, North America, South America and Antarctica all had their hottest September on record. Alongside higher land temperatures, sea surface temperatures have been at record high levels since April this year.

The average temperature for 2023 will very likely be more than 1.5°C above pre-industrial levels. A breach of the Paris Agreement goal would require temperatures to be sustained above 1.5°C for at least 20 years, so this does not mean we have blown our chance. However, the fact that we are increasingly seeing average monthly temperatures above this goal signals that we are getting closer.3The Paris Agreement – a legally binding international treaty on climate change – set a goal to limit “the increase in the global average temperature to well below 2°C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels.”

Global warming fuels extremes

Temperature extremes such as those recorded this year are occurring in a planet that has already warmed to unprecedented levels – the past eight years were the warmest on record. The speed of this warming has accelerated over the last decade, reaching an unprecedented rate of more than 0.2°C over 2013–2022. Scientists attribute this to record-high greenhouse gas emissions and reduced aerosols – particles in the atmosphere that scatter or absorb the sun’s radiation. Every fraction of a degree of warming at the global level increases the odds of additional, and often extreme, impacts at regional and local levels. With the increased build-up of greenhouse gases in the atmosphere, heatwaves are becoming hotter and more frequent. As emphasised by climate scientist Sarah Perkins-Kirkpatrick, “It only takes a small change in average temperature for the frequency of extremes to completely blow out, which is what we’ve seen in the Northern Hemisphere recently”.

The global temperature is an average taken from across the world, with actual temperatures at different locations ranging from much lower to much higher, meaning the impacts of warming are unequally distributed. For example, average July temperatures in some parts of northern Canada this year were more than 7°C above the 30-year average.4Parts of northern Canada fall within the Arctic, which has been warming at four times the rate of the global average over the last four decades. This extreme heat, combined with unusually dry conditions, fuelled unprecedented wildfires in the region, highlighting how temporary spikes in temperature combined with longer-term elevated warming can have devastating consequences.5The extent of burned area by the end of July was twice as high as the previous record for the whole of 1995. “Summer 2023’s record-setting temperatures aren’t just a set of numbers – they result in dire real-world consequences,” said NASA Administrator Bill Nelson.

Events such as wildfires may have knock-on effects that fuel further warming: the fires in Canada this year have released record-high carbon emissions, risking the creation of a self-perpetuating cycle that speeds up warming, known as a positive feedback loop.6More than double the wildfire emissions of a previous record-high year. Warmer, drier conditions as a result of climate change create the conditions for wildfires, and wildfires further fuel climate change by releasing stored carbon and reducing the carbon sink capacity of forests as they burn down, which then creates warmer and drier conditions, ultimately locking us into more warming.

Climate is complex

While the overall warming trend does not come as a surprise to scientists and matches projections by climate models, the extent to which temperature records have been broken this year – particularly the 0.5°C September anomaly – is remarkable. This is because temperature records are typically broken by margins of 0.1 or 0.2°C. To better understand this anomaly, scientists scrutinised over 150 outputs from climate models to work out the chances of a 0.5°C September anomaly. They found that the chance is very low – roughly 1 in 10,000 in any given September.

Some models may not be fully capturing certain processes that add to warming. Recent developments in policy, leading to reduced pollution for example, have occurred faster and in different places than previously anticipated. Similarly, the impacts of natural processes – which are infinitely complex – can be difficult to predict: a volcanic eruption in the South Pacific last year was unusual in that it may have had a warming effect rather than a cooling effect due to an uncharacteristically low level of sulphur dioxide.

The Earth’s climate system is made up of complex dynamics and interactions among various natural and human-caused processes. Exact future temperatures are hard to predict, and will become harder as the world warms and weather becomes harder to forecast. However, we do know that rising heat will have catastrophic consequences, and we should do everything in our power to limit overall warming as soon as possible.

Interplay between long-term warming and natural variability

Air temperatures on earth have a natural degree of variability due to factors such as changes in solar radiation, ocean-atmosphere interactions and volcanic eruptions. This inherent variability means that even if there was no global warming, average global temperatures would not be identical from year to year. However, it is clear that global warming – fuelled by the long-term build-up of greenhouse gases in the atmosphere from burning fossil fuels – is driving the persistent upward trend in global average temperatures since industrial times, and that the natural variability of the climate system has had very little impact on this trend.

Contributors to temperature spikes

Though global warming is a gradual process that can’t solely explain the sharp uptick in temperatures observed this year, a number of other factors – such as an emerging El Niño, an unusual volcanic eruption in the South Pacific, and decreased sulphur dioxide emissions from shipping – are acting on top of a high baseline global temperature, edging us towards record-breaking heat at increasingly fast rates as the warming trajectory of the planet continues upwards (Figure 1).7Compared to the 1970-2014 period, climate models project global warming to be 40% faster in the period between 2015 and 2030. These other factors are responsible for the variability in temperatures – such as spikes in heat – witnessed at daily, monthly or yearly scales, but are not driving the persistent long-term warming trend. It just so happens that they are occurring all at once in an increasingly hot world. The exact contribution of these other factors to temperature spikes is highly variable and uncertain, with some playing very small roles.

Figure 1: Factors contributing to global temperature change over the last 10 years
Source: Berkeley Earth, August 2023 Temperature Update, 2023.
El Niño

El Niño is a natural climate phenomenon occurring every two to seven years whereby sea surface temperatures in the Pacific Ocean are warmer than average, causing short-term increases in global average temperatures as heat is pushed from the ocean into the atmosphere. El Niño events are often correlated with the hottest years on record. The previous hottest year on record, 2016, was during a “super El Niño event” – one of the three strongest in history. There is a growing scientific consensus that human-caused warming has, at least partly, made El Niño more variable and difficult to predict.
Some scientists have speculated that El Niño has been one of the main drivers of extreme heat this year, particularly as there was a rapid transition earlier this year from its cold counterpart La Niña, which has been in effect during the past three years.8The last La Niña event was a rare ’triple-dip’ event lasting three years, which was associated with various impacts and natural disasters around the world. Others are more cautious, pointing out that El Niño was only in its early phase at the onset of the record-breaking heat this year and that its biggest impacts are only anticipated in February to April next year. Temperatures typically respond around three months after El Niño peaks, which is only expected around the end of this year. There will likely be greater clarity on the role of El Niño in early 2024.

Warming oceans

Even before El Niño officially started this year, global average sea surface temperatures were already 0.1°C higher than the previous record, with marine heatwaves detected around the world. As the Pacific Ocean represents around half of the world’s ocean area – and El Niño originates in the Pacific – what happens in the Pacific will tend to have a significant impact on global sea temperatures.

Warming has also been exceptional in the North Atlantic Ocean, which in June was a record 0.5°C warmer than the long-term average, with localised extreme marine heatwaves of up to 5°C higher than average recorded. Natural variability in sea surface temperatures linked to the Atlantic Multidecadal Oscillation – a cyclical pattern of warm and cool sea surface temperatures – may partly explain these warmer temperatures. Research also shows that much of the heat stored in the subtropical North Atlantic is in deeper waters, with currents redistributing this heat to other regions of the ocean – believed to be a key driver of North Atlantic warming. At the same time, lower than average wind speeds in the northeastern Atlantic mean there is less mixing of colder ocean water from lower depths, causing sea surface temperatures to rise. Low winds also resulted in fewer dust particles – which scatter solar radiation back into the atmosphere before it can warm the ocean – being blown off the Sahara over the ocean. Similarly, reduced particulate pollution in North America and Europe, driven by policies on air quality, may have had a similar effect by reflecting less radiation.

It is important to remember that these processes – whether El Niño or reduced Saharan dust – are happening on top of an already warming ocean: more than 90% of global heat caused by greenhouse gas emissions has been absorbed by the ocean.9As oceans continue to warm, they will take up less heat from the atmosphere and cause global average surface temperatures to rise further. “Over the long term, we’re seeing more heat and warmer sea surface temperatures pretty much everywhere…[t]hat long-term trend is almost entirely attributable to human[s]”, said Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies. Unlike this long-term trend, changes in wind speeds or particulate pollution typically have very small impacts on longer-term temperature averages but do contribute to sudden spikes in temperature.

Low sea ice levels

Decades of warming has led to lower than average sea ice in Antarctica and the Arctic. Low sea ice levels may increase local warming, and at the same time, local warming may lower sea ice levels. Lower sea ice reinforces warming because less ice means less solar radiation reflected back into space and more radiation absorbed by the ocean, causing further warming and delaying sea ice growth. However, scientists are uncertain of the extent to which the lower sea ice influenced the warm conditions observed in Antarctica this year.

Volcanic eruption in the South Pacific

The lower sea ice and higher earth temperatures observed this year may have been influenced by the eruption of an undersea volcano in January 2022, which increased the amount of water vapour in the upper atmosphere, where it potentially acted as a powerful greenhouse gas and trapped heat. The additional warming caused by this eruption is not yet known, with some scientists speculating that its contribution is likely quite small, and others suggesting that more analysis is needed to fully understand the impacts.

Sulphur regulations

Researchers have suggested that regulations imposed on emissions of sulphur – a harmful air pollutant emitted by marine fuels – from shipping since 2020 could have also contributed to temperature spikes this year. This is because sulphur particles – which are harmful to human health – reflect radiation back into the atmosphere or block sunlight by forming ‘pollution clouds’, and their reduction has a warming effect. Estimates suggest that the cuts in particulate emissions from shipping regulations are equal to two additional years of human-caused greenhouse gas emissions at current rates. However, scientists caution that while a reduction in sulphur emissions may boost warming by around 0.045°C over the next few decades, it is unlikely to have any major influence on long-term global warming. 

As a counterbalance to temporary spikes in warming as aerosols are cleaned up, the Intergovernmental Panel on Climate Change (IPCC) recommends reducing human-caused methane emissions. While carbon dioxide remains in the atmosphere for a long time – up to 1,000 years – before breaking down, methane has a much shorter lifespan of around 12 years.10If we were to stop all methane emissions right now, global warming caused by methane would be halved in around 20 years. Methane also has more warming power as it absorbs more energy than carbon dioxide. This means that reductions in warming can be quickly achieved with methane emission cuts – reducing methane emissions from the energy sector alone could avoid up to 0.1°C of warming by mid-century.     

Solar fluctuations

Another natural phenomenon contributing to global temperatures is fluctuations in the output of the sun as part of the 11-year solar cycle. During this cycle, the average temperature of the earth increases by around 0.05°C. The current solar cycle is heading towards its peak, with the latest evidence suggesting that the sun’s activity has already reached levels not seen for 20 years. The current solar cycle is expected to peak between January and October 2024 – around the same time that the warming impacts of El Niño are expected to be greatest.

Overshooting 1.5°C of warming

The 2015 Paris Agreement aims to avoid “unleashing far more severe climate change impacts, including more frequent and severe droughts, heatwaves and rainfall”. The point in time where we breach 1.5°C of warming is getting dangerously close. Latest estimates show that we may only have six years left of emissions at current levels before our carbon budget runs out.

In the IPCC’s report on the impacts of 1.5°C of global warming, 90% of the emissions scenarios that limit warming to 1.5°C by 2100 include a period of ‘temperature overshoot’. Temperature overshoot describes when global average temperatures exceed 1.5°C (or 2°C) of warming before returning to that level at some point in the future. In most of the IPCC pathways – which describe different levels of greenhouse gas emissions for reaching a certain level of warming – global average temperatures exceed the target for at least one decade and up to several before dropping back down – achieved through the deployment of carbon dioxide removal.11Many pathways limiting warming to 1.5°C rely on the deployment of carbon dioxide removal technologies, which are ‘uncertain and entail clear risks’.

The magnitude – how much the specified level of warming is exceeded – and the duration – how long that level of warming is exceeded – differ across scenarios. Keeping the magnitude and duration of overshoot as low as possible is critical if we are to avoid the worst climate impacts to people and the planet. Every fraction of a degree of overshoot increases the severity, frequency and duration of climate impacts, such as heatwaves, as does whether we meet temperature targets early in the century or not. In addition, the closer we stick to 1.5°C, the better the economic outcome. Climate impacts from temperature overshoot will lead to higher mitigation costs and economic losses later in the century.12While higher initial investments are needed to keep temperatures down, this is outweighed by the economic benefits later in the century.

Tipping points

Scientists warn that overshooting 1.5°C – even temporarily – could have devastating and irreversible impacts. Numerous ‘tipping points’ could be crossed with just 1.5°C of warming. These are critical thresholds at which the global climate system tips into another state, triggering feedback loops and catalysing large and often irreversible changes to the climate.

One tipping point is the drying of the Amazon rainforest, caused by deforestation, fires and less rainfall, which could transform this critical carbon sink into a savanna. This would not only impact the millions of people and animals living in the region, but would result in billions of tonnes of carbon dioxide being released into the atmosphere – further fuelling global warming – as well as less rainfall and changes to global climate patterns. 

In addition to triggering tipping points, overshoot could temporarily push thousands of species beyond the range of temperatures at which they can survive. For some species, life may not fully recover after overshoot: even temporary overshoot could cause irreversible extinctions and lasting damage to tens of thousands of species, with knock-on effects for entire ecosystems. If we are to limit warming to 1.5°C with limited or no overshoot, deep, rapid and immediate reductions in emissions are essential.

Solutions

Cutting emissions

Emissions are at an all-time high and are rising, with atmospheric carbon dioxide levels higher than they have been for at least four million years. Continued warming means land and ocean carbon sinks will become increasingly less effective at slowing the accumulation of carbon dioxide in the atmosphere. If reductions in emissions are achieved now, there would still be a lag in the warming response of the earth.13If we stopped all greenhouse gas emissions today, there’s still a 42% chance that we would overshoot 1.5°C. However, pursuing strict mitigation measures to keep warming under 1.5°C with limited or no overshoot would substantially reduce climate risks over the next 20 years and allow societies and ecosystems to avoid the worst impacts of climate change. To do this, net carbon dioxide emissions would need to be reduced by 48% by 2030, according to the IPCC.

The fastest and cheapest way to deliver emissions cuts is to reduce our reliance on fossil fuels for energy and switch to renewable-powered electricity. To limit warming to 1.5°C with limited or no overshoot, the use of coal would need to be reduced by 100%, oil by 60% and gas by 70% by 2050.14This is assuming no carbon capture, storage and utilisation. There would need to be increased electrification of energy, with almost all electricity coming from zero-carbon or low-carbon sources. Since 2010, solar and wind power have become cost-competitive with fossil fuels globally – the current average levelised cost of solar photovoltaic is almost one-third less than the cheapest fossil fuel.15The levelised cost is the price at which electricity should be sold for the system to break even at the end of its lifetime. In 2022, electricity fuel costs of USD 520 billion were saved as a result of renewable capacity added since 2010. Rapid renewables deployment – around 1,000 GW per year until 2030 – will be critical for keeping warming to 1.5°C.

Reducing methane

One promising solution for rapidly reducing global warming involves cutting emissions of methane – which has contributed around one-third of global warming since pre-industrial times. Methane concentrations in the atmosphere have been rising dangerously quickly since around 2007, and have reached record levels in recent years. Due to its short lifespan, cutting methane emissions offers the “single fastest, most effective way to slow the rate of warming right now”. It is also one of the cheapest ways to reduce warming. By using cost-effective measures such as reducing leaks from pipelines, shutting down abandoned oil wells and reducing livestock numbers, human-caused methane emissions could be reduced by up to 45% by 2030, avoiding nearly 0.3°C of warming by the 2040s.16UNEP, Global Methane Assessment, 2021. Pg 8. https://www.unep.org/resources/report/global-methane-assessment-benefits-and-costs-mitigating-methane-emissions According to the IPCC, a reduction of 34% is needed by 2030, along with cuts to other greenhouse gas emissions, to achieve 1.5°C with limited to no overshoot without relying on carbon dioxide removal.

Agriculture, and particularly livestock farming, is the single largest source of methane emissions from human activity, and livestock emissions are expected to increase by up to 16% by 2030. Through reducing livestock numbers, improving livestock nutrition and breeding, and reducing food loss and waste, significant reductions in warming from methane can be achieved in the next few decades. According to the International Energy Agency, technology to reduce methane emissions from fossil fuel operations – which account for around 40% of methane emissions from human sources – already exists and could cut around 70% of emissions from this sector.

Carbon dioxide removal

Proposed solutions for reducing warming can be nature-based, such as planting trees which store carbon in their tissues, or growing crops, burning them for energy, and storing the released carbon. There are also technological solutions, such as machines that suck carbon dioxide from the atmosphere and store it long term, called direct air capture and storage. Collectively, these approaches are referred to as carbon dioxide removal (CDR).

There are major uncertainties with both nature-based and technological solutions: forests burn down, risking the release of stored carbon, and there is limited space for planting trees. Growing energy crops requires large areas of land, which could potentially endanger biodiversity through the conversion of natural land or threaten human food security by supplanting food crops. Machines for drawing carbon from the atmosphere are not yet fully developed and are expensive, and none of these solutions have been shown to work at the scale needed. The world’s largest direct air capture plant only saves us 3 seconds of emissions per year. Atmospheric physics and the changing nature of forests as carbon sinks are also not fully understood, but current evidence suggests that CDR may not compensate for emissions on a like-to-like basis. The reduction in atmospheric carbon dioxide achieved by deploying CDR may be less than 10% of the carbon dioxide released into the atmosphere from an equal amount of emissions.

Forest carbon offsets – under which companies or individuals can purchase credits for preserving a forest or planting a tree that is equal to the amount of carbon to be offset in order to achieve their net-zero pledges – have been shown to be ineffective and are marred by alleged greenwashing and dubious accounting methods.

The uncertainty around the effectiveness of these technologies offers a strong incentive for ramping up climate action in the near-term to reduce our reliance on them. However, because emission reductions have been so delayed, some amount of CDR will be necessary to meet 1.5°C, together with decarbonisation of energy and electricity, electrification, and deep emissions cuts, particularly of methane. In IPCC pathways that limit warming to 1.5°C with limited or no overshoot, CDR is only used in sectors for which no mitigation measure is available and to counterbalance historical emissions. The longer we delay emissions cuts, the more we will have to rely on unproven technologies to reduce warming and risk large-scale, irreversible impacts on society and nature.

Immediate, meaningful action now can bring benefits within our lifetime. Bold pledges and policies, stricter net-zero standards, and strengthened accountability are needed to deliver real and immediate emissions cuts.

The impacts of El Niño on a warming planet

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Key points:

  • El Niño is a natural climate phenomenon, typically lasting 9-12 months, that has been linked to crop failures, more frequent wildfires and concurrent droughts, increased flood risk, disruptions to fisheries, elevated civil conflict and increased disease risk in various regions
  • Present forecasts predict an 84% chance of at least a moderate El Niño and a ±56% chance of a strong El Niño for 2023-2024
  • The first year that we see average temperatures exceed 1.5°C could be during El Niño. While this would not mean that the Paris Agreement target has been transgressed, it is a reminder that we are getting closer to this threshold    
  • The frequency and severity of El Niño events increased in the latter part of the 20th century, and climate change is projected to further increase both, as well as making these events more difficult to predict
  • El Niño involves complex interplay among various atmospheric phenomena, making its impacts difficult to predict. However, it is associated with some general weather trends around the world, including:
    • Increased rainfall and flooding risk in East Africa, northern Mexico, the southern US, Peru and Ecuador  
    • Elevated fire risk in Indonesia, Australia and the Amazon 
    • Drought conditions in India, southern Africa, the Philippines, Indonesia, the Amazon and Australia  
    • Warm conditions in Canada and the northern US
  • Countries and ecosystems are already experiencing impacts from climate change, such as heatwaves, droughts and floods, and El Niño is likely to make these impacts worse.

El Niño

First described by Peruvian fishermen in the late nineteenth century as warm ocean waters around Christmas time that disrupt fishing conditions, El Niño is a natural climate phenomenon in which sea surface temperatures in the tropical Pacific are warmer than average. Under normal (or neutral) atmospheric conditions, trade winds – the east-to-west winds that blow along the earth’s equator – transport warm water from South America to Asia, which is then replaced by cooler water from lower depths. This process, referred to as upwelling, brings nutrients to the surface water, creating fertile fishing grounds. During an El Niño event, the trade winds weaken, causing warm water to accumulate in the Pacific Ocean. By contrast, when the trade winds are strong, the opposite happens and more warm water is transported to Asia – called a La Niña event. These two opposing processes – El Niño and La Niña – make up the El Niño-Southern Oscillation (ENSO) cycle. 

In the past, ENSO events were described as Eastern-Pacific (EP) events, because the Eastern Pacific was where the maximum warming was located. However, the last four decades have seen an increase in the frequency of Central-Pacific (CP) events,1CP El Niño events are also referred to as “El Niño Modoki” and “warm pool El Niño”. where the maximum warming is located in the central equatorial Pacific. The characteristics and associated impacts of these two events differ.2EP ENSO has stronger El Niño events compared to La Niña events, whereas CP ENSO has stronger La Niña events compared to El Niño events.   

The latest El Niño forecast, issued in June this year by the National Oceanic and Atmospheric Administration, states that El Niño has started and is expected to gradually strengthen during the Northern Hemispheric winter of 2023-2024. There is a ±56% chance of a strong El Niño and an 84% chance of a moderate El Niño. This prediction comes after an unusually long La Niña event lasting three years came to an end earlier this year. This was linked to catastrophic flooding in South-east Asia and Australia, particularly in Pakistan, where flooding displaced around eight million people, as well as the most severe drought in recent history in the Horn of Africa, which has left millions of people displaced and at risk of starvation.

Impacts of El Niño

Though the effects were originally thought to be localised to the coastal regions of Peru and Ecuador, it is now known that the impacts of El Niño, as well as its cooler counterpart La Niña, are global and have been linked to crop failures, increased wildfire frequency, increased flood risk, heightened concurrent drought frequency, disruptions to fisheries, increased civil conflict and higher disease risk in various regions of the world.

El Niño and climate change

The occurrence of extreme El Niño and La Niña events has increased since the 1960s, and climate projections suggest the frequency of extreme ENSO events will increase in the future.3The IPCC AR6 WGI report states that “a robust increase in ENSO rainfall amplitude [used for defining extreme El Niños and La Niñas] is found particularly in SSP2‑4.5, SSP3‑7.0, and SSP5‑8.5… The changes in ENSO rainfall amplitude in the long-term future (2081–2100) relative to the recent past (1995–2014) are statistically significant at the 95% confidence [level]”.While climate models do not show consensus regarding changes in ENSO sea surface temperature variability, models that simulate extreme ENSO events do show large agreement. Some projections suggest a doubling of extreme El Niño events as global temperatures continue to rise.4The future period in the study included projections until 2090. CP El Niño events are expected to become more frequent with climate change, while EP events are projected to become more extreme. 

During the second half of the 20th century, various changes to the behaviour of ENSO were observed, including: 

  • An increase in the occurrence of CP El Niño events   
  • Increased frequency of more extreme El Niño and La Niña events  
  • Increased variability of both CP and EP ENSO events  
  • Changes in the origin of both CP and EP ENSO events since the 1970s from the western Pacific to the central and eastern Pacific. 

As ENSO is a naturally highly variable phenomenon, determining whether the characteristics of ENSO events since the 1950s are the result of human-caused global warming, or simply a reflection of this inherent variability, is not straightforward, partly because sea surface temperature records before 1950 are sparse and unreliable.5In the IPCC AR6 WGI report it states that “there is medium confidence that both ENSO amplitude and the frequency of high-magnitude events since 1950 are higher than over the period from 1850 and possibly as far back as 1400”. Estimates using paleoclimate proxy data – which can be found in coral fossils and tree rings, for example – suggest that ENSO variability intensified by around 25% during the latter part of the 20th century compared to pre-industrial times.6Paleo-reconstructions typically have large uncertainty. A study published earlier this year estimates that human-caused warming has led to approximately one additional CP El Niño event and two additional extreme El Niño events since 1980. Despite the uncertainties, there is a growing consensus that human-caused warming is at least partly responsible for the changes in ENSO variability since the 1960s.

Record high sea temperatures in April this year may also worsen the upcoming El Niño event. We are likely to see record-breaking temperatures with this year’s El Niño, which is occurring against a backdrop of a warming earth – the last eight years were the world’s hottest on record. The hottest of these was in 2016 during one of the strongest El Niño events on record, which saw unparalleled coral heat stress in the world’s oceans resulting in extensive coral bleaching and die-off. ‘Pulse heat stress’ events, such as El Niño, may compound climate change-related stresses on humans and other organisms, with potentially irreversible consequences.7For instance, the 1982/1983 ​​El Niño event led to the possible extinction of a coral species in Panama.

It is more likely than not that global average temperatures will temporarily exceed 1.5°C above pre-industrial levels for the first time in human history between 2023 and 2027.8A 66% chance of exceeding 1.5°C for one year, according to the World Meteorological Organisation’s Global Annual to Decade Climate Update. It is unlikely (33% chance) that the 5-year average temperature will remain above 1.5°C between 2023 and 2027.  During an extreme El Niño event, an extra 0.2°C could be added to the average temperature of the earth on top of elevated temperatures due to global warming. The first year that we see average temperatures exceed 1.5°C could be during El Niño. While this would not mean that the Paris Agreement target has been transgressed, it is a reminder that we are getting closer to this threshold.9Breaching the Paris Agreement target of 1.5°C of warming since pre-industrial times – a threshold seen as important for limiting the impacts of climate change on people and nature – would require several decades of average temperatures above 1.5°C.  

Countries and ecosystems are already experiencing climate change-induced impacts, such as heatwaves, droughts and floods, and El Niño is likely to make these impacts worse. It has also been suggested that continued global warming is making it increasingly difficult to predict El Niño events.

Regional impacts

Predicting whether an El Niño event will occur, or how intense it will be, is challenging, mainly because predictions need to consider changes in both the Pacific Ocean and the atmosphere. While the characteristics of every El Niño event are different, our understanding of ‘teleconnections’ – whereby a climatic pattern, such as El Niño, is correlated with weather patterns elsewhere in the world – can be used to make predictions about the possible impacts. The figure below shows the typical weather impacts of El Niño across the world.

Source: National Oceanic and Atmospheric Administration
Africa

In East Africa, El Niño conditions tend to result in wetter ‘short rains’ (the second rainy season in November and December), which can cause flooding. There is also a strong link between the Indian Ocean Dipole (IOD) – the Indian Ocean counterpart of El Niño and La Niña, in which there is a difference in sea surface temperatures between the western and eastern Indian Ocean – and El Niño. When there is a positive IOD and EP El Niño, wetter short rains are amplified. 

In southern Africa, drier than average conditions are expected under El Niño, resulting in decreased maize yields, while the opposite is anticipated in East Africa. In Kenya, the higher rainfall associated with the 2015-2017 El Niño cycle increased maize production by 17%, while drought conditions in southern Africa during the same period reduced maize yields by up to 50%, caused the death of around 634,000 cattle, and resulted in more than 20 million people needing humanitarian aid. By contrast, wheat yields in South Africa may benefit from El Niño. 

During and after El Niño events, cholera incidence has been found to increase threefold in El Niño-sensitive areas in East Africa due to higher rainfall.

India

For India, El Niño tends to weaken the monsoon rains and produce drier conditions, and experts warn that when an El Niño event follows from a La Niña year – as is the case in 2023 – the monsoon rains may be particularly low.10Though this is dependent on various factors, such as lower Eurasian snow cover, which creates warmer conditions on the subcontinent, thereby bringing more rain to India. An assessment of rainfall trends over 132 years in India shows that severe droughts in the region have always been during El Niño years. Additionally, a CP El Niño event impacts the monsoon more than an EP event, but if an EP event occurs, there is also a higher possibility of a positive IOD occurring, which brings drier conditions to the eastern Indian Ocean (in the region of India) but wetter conditions to the western Indian Ocean (in the region of eastern Africa).

Southeast Asia

In Java, Indonesia, El Niño tends to decrease rainfall. Decreased rainfall during El Niño periods has been linked to increased forest fires in Indonesia and reduced rice yields on Java. where more than 50% of the country’s rice is grown. Fires in Indonesia are more intense and prolonged under an EP El Niño, and southern Kalimantan has experienced more intense fires than southern Sumatra under all El Niño events. However, fires are shorter and less intense during El Niño phases when the IOD is negative or weakly positive.     

In the Philippines, El Niño is associated with a decrease in average rainfall and elevated drought conditions, particularly during December to May. The associated water shortages may negatively impact agricultural production in the region – the 2015/2016 El Niño event cost USD 327 million in agricultural production losses. In China, El Niño is linked to higher wintertime air pollution due to southerly winds that encourage the accumulation of particulates.

Europe

El Niño winters are associated with wetter conditions in southern Europe and colder, drier conditions in northern Europe.

Australia

In Australia, El Niño is expected to bring higher temperatures and fire risk, and lower rainfall. Australia is warming faster than some other regions on earth – being 1.4°C warmer than it was during pre-industrial times – potentially making it particularly vulnerable to the effects of El Niño.

North America

In the Northern US and Canada, El Niño is associated with warmer conditions, whereas in the southern US and northern Mexico, wetter, cooler conditions with increased flooding risk are expected. El Niño weakens Atlantic hurricane activity but increases Pacific hurricane activity. 

El Niño may reduce wheat yields in the US as well as maize yields in the southeastern US, while soybean yields may increase.  

South America

El Niño typically brings heavier rains and flooding risk to Ecuador, Peru and Uruguay, A CP El Niño brings drier conditions to the tropical Andes and northern South America, but wetter conditions to southeastern South America and the Peruvian Amazon. An EP El Niño is linked to higher rainfall in Ecuador and Peru and dry conditions in northeastern Brazil, the Amazon Basin and the Andean Plateau. Specifically, an EP El Niño is associated with reduced rainfall in northern, eastern and western Amazonia, with significant impacts on water and carbon cycling – whereby carbon atoms are cycled between the atmosphere, organisms and minerals on earth. During EP El Niño events, lower rainfall occurs across all seasons in the Amazon, turning the Amazon into a net carbon source as trees dry out and slow their growth. During CP El Niño events, reduced rainfall is only observed during the summer wet season. Increased drought may drive forest fires and biome transformation in the Amazon. Warmer, drier conditions in Colombia during El Niño have been linked to outbreaks of dengue fever and malaria.

El Niño may positively affect maize production in Argentina and Brazil, soybean and rice production in Brazil, and wheat production in Argentina due to cooler and wetter conditions. In Mexico, El Niño could reduce maize and wheat output.

  • 1
    CP El Niño events are also referred to as “El Niño Modoki” and “warm pool El Niño”.
  • 2
    EP ENSO has stronger El Niño events compared to La Niña events, whereas CP ENSO has stronger La Niña events compared to El Niño events.   
  • 3
    The IPCC AR6 WGI report states that “a robust increase in ENSO rainfall amplitude [used for defining extreme El Niños and La Niñas] is found particularly in SSP2‑4.5, SSP3‑7.0, and SSP5‑8.5… The changes in ENSO rainfall amplitude in the long-term future (2081–2100) relative to the recent past (1995–2014) are statistically significant at the 95% confidence [level]”.While climate models do not show consensus regarding changes in ENSO sea surface temperature variability, models that simulate extreme ENSO events do show large agreement.
  • 4
    The future period in the study included projections until 2090.
  • 5
    In the IPCC AR6 WGI report it states that “there is medium confidence that both ENSO amplitude and the frequency of high-magnitude events since 1950 are higher than over the period from 1850 and possibly as far back as 1400”.
  • 6
    Paleo-reconstructions typically have large uncertainty.
  • 7
    For instance, the 1982/1983 ​​El Niño event led to the possible extinction of a coral species in Panama.
  • 8
    A 66% chance of exceeding 1.5°C for one year, according to the World Meteorological Organisation’s Global Annual to Decade Climate Update. It is unlikely (33% chance) that the 5-year average temperature will remain above 1.5°C between 2023 and 2027. 
  • 9
    Breaching the Paris Agreement target of 1.5°C of warming since pre-industrial times – a threshold seen as important for limiting the impacts of climate change on people and nature – would require several decades of average temperatures above 1.5°C.
  • 10

Loss and Damage in the Sundarbans

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Key points:

  • The Sundarban region, home to 7.2 million of the world’s most vulnerable people and the largest single mangrove forest in the world, is increasingly at threat from catastrophic impacts of climate change
  • Climate change is contributing to the absence of employment opportunities, the destruction of property from extreme weather events and the loss of vital mangroves and land from sea level rise. With homes and livelihoods under threat, many are left with no choice but to migrate elsewhere
  • The increasing scale and frequency of climate impacts mean the limits of adaptation have already been reached in many cases. The most affected argue that the extensive loss and damage needs to be addressed by those responsible with the financial means to do so.

What are the Sundarbans?

The Sundarbans are a cluster of low-lying islands in the Bay of Bengal, spread across India and Bangladesh. The region is recognised internationally for its unique biodiversity and ecological importance – including the single largest mangrove forest in the world, encompassing a total area of 10,200 km2.  

The Sundarbans ecosystem offers a wide range of vital ecological services, including cyclone protection for millions of people, wildlife habitat, food and natural resource provision, and carbon sequestration. It is also home to about 7.2 million people (4.5 million in India and 2.7 million in Bangladesh), including some of South Asia’s poorest and most vulnerable communities. Around half the population lives below the poverty line.

Due to a lack of employment opportunities, most are dependent on the land and natural resources that are increasingly being depleted by climate change. Most rely on subsistence agriculture, supplemented with fishing, crab and honey collection. Millions are unable to meet their basic nutritional requirements, leading to health issues such as anaemia, malnutrition and childhood stunting. At the same time, climate impacts are exacerbated by other factors, such as poverty, lack of livelihood options, reliance on land, uneven land ownership and limited government support.

The Sundarbans were declared a reserve forest before the partition of India in 1875, and UNESCO declared the Indian and Bangladesh portions of the Sundarbans World Heritage Sites in 1987 and 1997, respectively. The region is also recognised under the Ramsar Convention on Wetlands. Despite this recognition, including conservation obligations under international conventions and treaties, the Sundarbans are under threat from climate change, along with a combination of natural factors and human impacts.

Climate impacts in the Sundarbans

Land mass is declining year by year

In 2015-16, the total area of the Sundarbans had shrunk  by 210 km2 since 1967, and by 451 km2 since 1904. This declining trend holds true whether the Indian and Bangladesh portions of the Sundarbans are considered separately or grouped together. The main reason is the surrounding sea level, which is rising more than twice as fast as the global average. Satellite imagery shows the sea level has risen in the Sundarbans by an average of three centimetres a year over the past twenty years, and the area has lost almost 12% of its shoreline in the last forty. In addition to sea level rise, a gradual reduction in sediment flow from rivers to the Sundarban region has resulted in loss of land mass. 

Due to these factors, the rate of retreat of coastlines is as high as 40m a year for some of the islands, which will disappear completely within the next 50–100 years at the current rate. Already some islands have been submerged and it is predicted that many more will vanish if sea level rise maintains its current pace.

Salinisation is threatening agriculture and health

Where land is not yet lost, frequent flooding with salty water from rising sea levels and extreme weather events renders affected land unproductive. Increasing water and soil salinity are also caused by climate-induced changes in temperature and rainfall, along with reduced freshwater flows from the Himalayas in the dry season. In the last 40 years, approximately 25% of glacial ice has been lost in the mountain range, posing a significant risk to stable and reliable freshwater supplies to major rivers, such as the Ganges and Brahmaputra, that flow into the Sundarbans. 

In the Sundarban region, water and soil salinity has increased dramatically, with projections that many parts of the region will reach near ocean-level salinity by 2050. In Bangladesh, soil salinity increased six times, and up to fifteen times in certain areas, from 1984 to 2014. The salinisation of soil ruins crops and devastates farmer livelihoods. Research estimates a one metre increase in sea level would cause losses as high as USD 597 million in agriculture from salinity-induced land degradation. Some villages no longer support agriculture due to recurrent salt water inundation. When households are no longer able to grow crops on land due to lack of access or salty soil, they are unable to engage in subsistence farming and are exposed to the cash economy, increasing their risk of food insecurity.

Progressive salinisation of rivers and groundwater has also resulted in the decline of available fresh drinking water, with numerous adverse effects on mother-child health, including dehydration, hypertension, prenatal complications and increased infant mortality. Collection of data from drinking wells in the Indian Sundarbans found that 17 out of 50 wells sampled contained salinity levels unsuitable for drinking. Increased saline water levels also cause high blood pressure and fever, as well as respiratory and skin diseases. A vulnerability assessment of Mousuni Island in the Sundarban region found that 80% of the villagers experienced skin disease caused by salty water. Additionally, 42% of households suffered infectious diseases, such as malaria and dengue fever, during flooding. Under high emissions scenarios, climate change is expected to make the prevalence of disease, particularly water-borne illnesses, even higher.

Mangroves and biodiversity are being depleted

Mangrove forests are a crucial natural blockade against cyclones, storm surges and tides, and sustain the high levels of biodiversity in the region. One study estimates that between 2000 and 2020, 110 km2 of mangroves disappeared from the reserve forest of the Indian Sundarbans due to erosion. While 81km2 of mangroves were gained through plantation and regeneration, the gains were all outside the existing mangrove forest. Another study looking at the coverage of mangrove forests between 1975 and 2020 found that mangrove forests have been decreasing in density by an estimated annual rate of 1.3%.

Researchers also observed a deterioration in the health of mangrove forests over the last twenty years due to increased salinity, temperature rise and rainfall reduction in pre and post-monsoon periods. While mangroves are known for their resilience, they are sensitive to changes in the salinity of water and soils, which is already resulting in shifts away from high-value timber species towards more salt-tolerant mangrove species. This is reducing the quality and overall availability of timber stocks, with implications for those relying on the forest for their livelihoods. Researchers estimate that there has been a loss of USD 3.3 billion in ecosystem services of the Sundarban Biosphere Reserve during the last 30 years, over 80% of which is provided by mangroves.

In a changing climate, it is expected that the Sundarbans landscape will undergo significant fragmentation, causing habitat loss for many endangered species, including tigers and venomous snakes, and this is increasing the risk of human-wildlife conflicts in the region. Sea level rise is resulting in habitat loss for many terrestrial and amphibian species. Habitats for freshwater fish are also shrinking as water becomes more salty, threatening many small, indigenous freshwater species. This has adverse impacts on the livelihoods of fishermen, as well as on human health as fish is a critical source of protein and nutrients in the Sundarbans. For example, in regions with high levels of fish species loss, chronic and acute malnutrition among mothers and children is higher than the thresholds set by the World Health Organization for public health emergencies.

Extreme weather events are more frequent and severe

While the Sundarban region has always been affected by cyclones and extreme weather events, the rate and intensity of these events are increasing. In the last 23 years, the area has witnessed 13 supercyclones. In the Bay of Bengal along the Sundarbans, the occurrences of cyclones increased by 26% between 1881 and 2001. Additionally, research has shown there has been a significant rise in the frequency of very severe cyclones in the post-monsoon season from 2000 to 2018. Scientists project an increase of about 50% in the frequency of post-monsoon cyclones by 2041-2060. 

The rise in cyclone frequency and severity is in part attributed to the increase in sea surface temperature, which rose in the Indian Sundarbans at 0.5°C per decade from 1980 through to 2007 – around eight times higher than the globally-observed warming rate of 0.06°C per decade. Land surface temperature in Sundarban region has already increased about 1°C over the past century and is projected to warm by up to 3.7°C by 2100.

Due to the low elevation of the Sundarbans and reduced protection from mangroves, cyclones can cause catastrophic damage. Four major cyclones have hit the Sunderbans in the last three years, killing nearly 250 people and causing losses of nearly USD 20 billion. Cyclone Amphan in 2020 was estimated to have destroyed 28% of the Indian Sundarban region and caused USD 12 billion of damage. The Cyclone displaced 2.4 million people in India and 2.5 million people in Bangladesh. While many returned soon afterwards, damage to more than 2.8 million homes and lack of evacuation centres resulted in homelessness and prolonged displacement for many thousands.

Following Amphan, the government estimates over 100,000 farmers experienced heavy losses as salt water in fields and ponds killed off fish and rendered fields uncultivable. With hundreds and thousands of extra mouths to feed, conflicts between humans and tigers spiked as islanders began venturing deep into the forests in search of fish, crab, honey and firewood.

Livelihoods are being hit hard

About five million people are dependent on the Sundarbans for their livelihoods. According to the World Bank, almost 80% of households in the Sundarbans pursue livelihoods that involve inefficient agriculture, fishing and aquaculture production methods. Dependence on the land and natural resources paired with a lack of alternative employment opportunities means livelihoods are extremely vulnerable to changing climatic conditions.

Salinisation is threatening agriculture. Fishermen are impacted by the decline in fish populations. Forest-based livelihoods are adversely impacted by changes in the composition of mangrove species, which is reducing the value of standing timber and honey production. A study of three villages in the Indian Sundarbans found that 62% of the workforce has lost their original livelihoods and have been forced to rely on much more uncertain incomes. 

Even though the impacts of climate change put their livelihoods at greater risk, some households continue to live in vulnerable locations due to high land prices and a lack of employment opportunities elsewhere. Due to a lack of job opportunities, others need to migrate to seek out employment, temporarily or sometimes permanently. 

Young men and women have had to leave for nearby cities, or even states over 1,000 kilometres away. There they face a precarious existence as daily wage labourers and contract workers at construction sites and factories. Some estimates suggest that roughly 60% of the male workforce in the Indian Sundarbans has migrated. Migration has also increased the poverty of the population left behind since it takes considerable time for low-skilled migrant family members to save sufficient funds to send back home.

Migration as a last resort

An estimated 1.5 million people will have to be permanently relocated outside the Sundarbans because sea level rise will make it impossible for them to live there or earn a livelihood. As climate change is responsible for their forced migration, these people are climate refugees – however, the term is not formally recognised internationally.  Additionally, extreme poverty both arises from and contributes to their vulnerability to environmental hazards. 

Over the past 25 years, four islands in the Indian Sundarbans – Bedford, Lohachara, Kabasgadi and Suparibhanga – have already disappeared, causing 6,000 families to become displaced. Lohachara became well-known as the first inhabited island in the world to disappear. Neighbouring Ghoramara is already half underwater. Once home to 40,000 people, the 2011 census counted only 5,000 people still struggling on the island. 

Many of those displaced relocated to nearby Sagar island with the aid of government programmes in the 1980s and 1990s. However, with a population of 200,000 and growing, and with the island having shrunk by a sixth of its original size, land and resources are being severely depleted. One case study calculated the total value of damage to 31 households forced to move from inundated areas of the Sundarbans to the island of Sagar at Rs 6,0742,225 crore (USD 700,000), 98% of which was due to loss of land assets. 

Back in 2002, it was estimated that climate change would displace over 69,000 people from the Sundarbans by 2020. In 2018, about 60,000 people had already migrated from the region.

Why adaptation is not enough

Climate adaptation is the process of adjusting to current or expected effects of climate change. However, it is clear that adapting to some impacts of climate change will not be possible and, in some cases, the limits of adaptation have already been reached. 

A key adaptation measure is the construction of storm surge walls and embankments. However, even with these measures, the loss and damage inflicted by a few hours’ battering by waves, winds, and storm surges during a cyclone can undo the gains from many years of measures to prevent flooding. After Cyclone Aila in 2009 destroyed 778 km of embankments in the Sundarbans, it cost Rs 5,032 crore (USD 670 million) to rebuild them, only for them to be breached again ten years later by Cyclone Amphan. One Sundarban village, after embankments to hold back the rising sea collapsed during Cyclone Aila, attempted three times to build sea walls, all of which collapsed against the power of the sea. 

Another adaptation approach is the introduction of salt-resistant crops. This has been met with some success, but may prove to be a temporary fix, with hurdles such as the availability of seeds, knowledge of farming and relatively low yields. 

Adaptation practices can also exacerbate and accelerate the ecological damage caused. For example, increasing salinity levels prevent the cultivation of rice or other crops, causing some to shift towards shrimp farming, which requires salt water and can be more profitable. However, the conversion of land to shrimp farms further accelerates the salinisation of water while profits often only benefit private investors. Workers – primarily women – receive little income and suffer health issues, such as infections, problems with eyesight and skin disease.

For the people of the Sundarbans, lives depend upon the land on which they live, produce food and sustain their livelihoods. Some inhabitants have already had to relocate multiple times. In the words of one resident: “People are resilient, but how much resilience can they have?” The outlook is bleak for the Sundarbans, with proposals that ‘managed retreat’ – the planned migration away from vulnerable regions over time – may be the only viable option.

Why financing for Loss and Damage is needed

Loss and damage is a term used to describe how climate change is already causing serious and, in many cases, irrevocable impacts around the world – particularly in vulnerable communities. According to the most recent assessment of climate impacts from the Intergovernmental Panel on Climate Change (IPCC), loss and damage can broadly be split into two categories – economic losses involving “income and physical assets”, and non-economic losses, including “mortality, mobility and mental wellbeing losses”. 

For the people of the Sundarbans, the economic and non-economic losses, such as loss of land, livelihood, mortality, health, culture, are beyond what the region can afford. According to a 2009 study, the annual costs of the environmental damage and health issues caused by climate change are estimated at Rs 1290 crore annually (USD 250 million) – equivalent to 10% of the Sundarbans GDP in 2009. 

The Sundarbans bear little responsibility for global emissions (for example, the whole country of Bangladesh is accountable only for only 0.56% of global emissions), but are forced to suffer the consequences. Alongside many other developing nations and vulnerable communities, the region argues strongly that it should not be forced to pay for the excessive loss and damage already incurred, and anticipated in the future.

Key takeaways from the three working group reports of the IPCC sixth assessment

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Key points

  • Climate change is unequivocally caused by human activities as a result of burning fossil fuels, industrial processes and land use change and it is a threat to human well-being and planetary health.
  • Losses and damages from climate change will increase rapidly with further warming, in many cases creating risks that people and nature will be unable to adapt to. If emissions are cut at the rate currently planned, the resulting temperature rise will threaten food production, water supplies, human health, coastal settlements, national economies and the survival of much of the natural world.
  • To prevent further warming, urgent emission reductions across all sectors and rapid scale up of electrification are needed to reduce emissions and keep warming to 1.5°C by the end of the century. However, even the most ambitious scenarios indicate global temperatures will temporarily overshoot 1.5°C.
  • Models from the Working Group 1 and 3 report both indicate that deep reductions in other greenhouse gases, particularly in methane emissions, will help lower peak warming. 
  • Any further delay in concerted global action on adaptation and mitigation will miss a brief and rapidly-closing window of opportunity to secure a liveable and sustainable future for everyone.

IPCC’s sixth assessment cycle 

Between 2020 and 2022, the Intergovernmental Panel on Climate Change (IPCC) released three reports from its sixth assessment cycle covering the latest science on the physical state of the global climate (Working Group 1, WGI), the impact of climate change (Working Group 2, WGII) and mitigation of climate change (Working Group 3, WGIII). 

The sixth assessment cycle (AR6)  included 782 scientists, who worked on a voluntary basis, with 67 countries contributing to create the most authoritative assessment of climate change to date. 

This briefing summarises key themes that run through these three reports: 

  • The human-driven impact of climate change
  • The cause and current trajectory of our climate crisis
  • The speed and scale of the transformation required to achieve a safe(r) climate

Climate change is happening all around us 

The term “unequivocal” was used in both WG1 and WG2 to describe the scientific consensus that the climate is changing as a result of human activity, representing a threat to human well-being, societies and the natural world.1WG1, SPM A.1, WG2, SPM D.5.3. Human actions have warmed the climate at a rate that is unprecedented in at least the last 2,000 years, increasing the frequency and intensity of extreme weather events across the world. 2WG1, SPM1.WG2,SPM B.1.1 The physical impact of climate change is causing substantial damages and, in some cases, irreversible losses.3WG2,SPM B.1.1 

The WG2 report emphasised that we have a brief and rapidly-closing window of opportunity to secure a liveable future. Additionally, WG3 stressed that without urgent, effective and equitable mitigation, climate change increasingly threatens the health and livelihoods of people around the globe, ecosystem health and biodiversity.4WG2, SPM D.5.3 and WG3, SPM D.1.1

National commitments made by governments prior to COP26 are not enough to limit warming to 1.5°C and are likely to lead to global warming of 2.8°C by 2100. 5WG3, SPM B.6.WG3, SPM C.1.1. Both WG1 and WG3 reports agreed that even in the most ambitious emissions reduction scenario, it is more likely than not that global warming will reach 1.5°C by 2030 and overshoot to 1.6°C, before dropping back down.6WG1 Table SPM1, WG3, SPM Table SPM 2

The WG2 report described the devastating impacts of our current emissions pathway:

  • Food production and food security will be threatened by even a small amount of additional warming, which will cause increases in the severity and frequency of heatwaves, droughts and floods, along with sea-level rise7WG2, SPM B.4.3.
  • If warming reaches 2°C, there will be significant increases in ill-health and premature death as a result of more extreme weather and heatwaves, and disease spread8WG2, SPM B.4.4.
  • The extinction risk for unique and threatened species will be at least 10 times higher if temperature rise continues to 3°C, compared with if it is limited to 1.5°C.9WG2, SPM B.6.4.

Reliance on fossil fuels is the root cause of climate change 

Human activities around fossil fuel combustion, industrial processes, land use change and forestry have caused greenhouse gas (GHG) emissions to increase dramatically since pre-industrial times, and emissions were higher between 2010-2019 than in any previous decade.10WG3, SPM B.1, Footnote 6WG3, SPM B.1. Of the GHGs, CO2 has contributed the most to recorded warming to date, followed by methane.11WG1, Figure SPM2.WG1 D.1.7, Figure SPM2
In 2019, coal contributed to 33% of all human-related CO2 emissions, followed by oil (29%) and gas (18%).12WG3, Technical Summary, Figure TS.3. Public and private finance continue to flow into fossil fuels and, as a result, GHG emissions continue to rise across all sectors and subsectors, and most rapidly in transport and industry. 13WG3, Technical Summary, page 23.WG3, SPM B.5.4. Between 2019-2020, investment in fossil fuels was greater than that for climate adaptation and mitigation.14WG3, SPM B.5.4. In the power sector, fossil fuel-related investment was, on average, USD 120 billion a year. An average of USD 650 billion were invested in the oil supply and USD 100 billion in coal supply.15WG3, Chapter 15, 15.3.3. In comparison, actual global public finance flow for adaptation was USD 46 billion.16WG3, Chapter 15, 15.1.1.

Delayed climate action in reducing our reliance on fossil fuels is partly the result of a concerted effort to generate rhetoric and misinformation that undermines climate science and disregards risk and urgency.17WG2, Chapter 14, 14.3.1. This is particularly true in the US, where despite scientific certainty of the anthropogenic influence on climate change, misinformation and politicisation of climate change science has created polarisation in public and policy domains.18WG2, Chapter 14, 14.3.1.

People who have contributed the least to the existing climate crisis are likely to be the most vulnerable and least able to adapt. The richest 10% of households contribute about 36%-45% of global GHG emissions. About two thirds of the top 10% richest households live in developed countries.19WG3, Technical Summary, page 21. But increased heavy rain, tropical cyclones and drought will force more people from their homes, particularly in places that are more vulnerable and have less ability to adapt.20WG2 SPM B.4.7. 

Urgent, transformative change is needed to limit global warming

To limit warming to 1.5°C, we need to drastically reduce our reliance on fossil fuels for energy production and switch to widespread electrification using renewable energy generation. 21WG3, SPM C.3.2.WG3, SPM C.3.2. Changing how electricity is generated is especially important in transitioning our energy system, and in scenarios limiting warming to 1.5°C (with no or limited overshoot), the electricity sector reaches net-zero CO2 emissions globally between 2045 and 2055.22WG3, Chapter 6, Executive summary. In these scenarios, electricity supply rises to 48%-58% of final energy use by 2050 (in comparison to 20% in 2019).23WG3, Chapter 6, Executive summary. A combination of widespread electrification of all energy demand and a shift to renewable electricity systems that emit no CO2 will create co-benefits such as better health and cleaner air.24WG3, SPM C.4.1, SPM E.2.2.

We also need to have strong, rapid and sustained reductions in methane emissions. Models show that reducing methane emissions by a third by 2030 is needed to create a net cooling effect. 25WG3, SPM C.1.2.WG2, SPM D.1.7. Deep GHG emission reductions by 2030 and 2040 – particularly reductions of methane emissions – lower peak warming, reduce the likelihood of overshooting warming limits and lead to less reliance on net negative CO2 emissions that reverse warming in the latter half of the century.26WG2, SPM C.2.

Global use of coal, oil and gas (without CCS) is reduced by 100%, 60% and 70% respectively by 2050 in pathways that successfully limit warming to 1.5°C with no or limited overshoot.27WG3, SPM C.3.2. If not phased out, existing and planned fossil fuel infrastructure (without CCS) will make limiting warming to 1.5°C impossible.28WG3, SPM B.7

Rapid and deeper near-term GHG emissions reduction through to 2030 will lead to less reliance on carbon dioxide removal (CDR) in the longer term, but it is likely that we will need some CDR to counterbalance residual GHG emissions from hard-to-abate sectors.29WG3, SPM C.2.2, SPM C.3

CDR is not a ‘get out of jail free card’, especially at higher levels of warming because the ability of land and ocean sinks to sequester carbon will be greatly reduced at higher temperatures.30WG1, Figure 7 CDR also has limited ability to preserve existing ecosystems. If temperature rise passes 1.5°C, entire ecosystems will be irreversibly lost (including polar, mountain and coastal ecosystems, and regions that would be affected by ice-sheet and glacier melting),  even if temperatures are later reduced with measures to remove CO2 from the atmosphere.31WG2, SPM B.6.1

Some progress is being made

The WG3 report made it clear that there are mitigation options available in all sectors that could together halve global GHG emissions by 2030.32WG3, SPM C.12.1 Growing numbers of countries have seen the advent of cheap renewables that will power electric vehicles, heat pumps and other smart, emissions-free technologies. 

From 2010–2019, there were sustained decreases in the unit costs of solar energy (85%), wind energy (55%) and lithium-ion batteries (85%), and large increases in their deployment – for example >10x for solar and >100x for electric vehicles (EVs).33WG3, SPM Figure SPM 3 PV, onshore and offshore wind can now compete with fossil fuels on the levelised cost of energy in many places and electricity systems in some countries and regions are already predominantly powered by renewables.34WG3, Figure SPM 3, C.4.3 Large scale battery storage on electricity grids is increasingly viable.35WG3, Chapter 6, Executive summary

Electric vehicles are increasingly competitive against internal combustion engines, and it is the fastest growing segment of the automobile industry, having achieved double-digit market share by 2020 in many countries.36WG3, SPM Table TS.1  Electrification of public transport has been demonstrated as a feasible, scalable and affordable option to decarbonise mass transportation. 

There is also some green shoots evidence of climate policy beginning to have a positive real-world impact on emissions reductions that can be built on, for example:

  • At least 18 countries have now sustained production-based GHG and consumption-based CO2 emissions reductions for longer than 10 years.37WG3, SPM B.3.5
  • By 2020, over 20% of global GHG emissions were covered by carbon taxes or emissions trading systems, although coverage and prices have been insufficient to drive deep reductions.38WG3, SPM B.5.2
  • There are now ‘direct’ climate laws focused on GHG reduction in 56 countries covering 53% of global emission in 2020, and climate litigation is on the rise.39WG3, SPM B.5.2, E3.3
  • 1
    WG1, SPM A.1, WG2, SPM D.5.3.
  • 2
    WG1, SPM1.WG2,SPM B.1.1
  • 3
    WG2,SPM B.1.1
  • 4
    WG2, SPM D.5.3 and WG3, SPM D.1.1
  • 5
    WG3, SPM B.6.WG3, SPM C.1.1.
  • 6
    WG1 Table SPM1, WG3, SPM Table SPM 2
  • 7
    WG2, SPM B.4.3.
  • 8
    WG2, SPM B.4.4.
  • 9
    WG2, SPM B.6.4.
  • 10
    WG3, SPM B.1, Footnote 6WG3, SPM B.1.
  • 11
    WG1, Figure SPM2.WG1 D.1.7, Figure SPM2
  • 12
    WG3, Technical Summary, Figure TS.3.
  • 13
    WG3, Technical Summary, page 23.WG3, SPM B.5.4.
  • 14
    WG3, SPM B.5.4.
  • 15
    WG3, Chapter 15, 15.3.3.
  • 16
    WG3, Chapter 15, 15.1.1.
  • 17
    WG2, Chapter 14, 14.3.1.
  • 18
    WG2, Chapter 14, 14.3.1.
  • 19
    WG3, Technical Summary, page 21.
  • 20
    WG2 SPM B.4.7.
  • 21
    WG3, SPM C.3.2.WG3, SPM C.3.2.
  • 22
    WG3, Chapter 6, Executive summary.
  • 23
    WG3, Chapter 6, Executive summary.
  • 24
    WG3, SPM C.4.1, SPM E.2.2.
  • 25
    WG3, SPM C.1.2.WG2, SPM D.1.7.
  • 26
    WG2, SPM C.2.
  • 27
    WG3, SPM C.3.2.
  • 28
    WG3, SPM B.7
  • 29
    WG3, SPM C.2.2, SPM C.3
  • 30
    WG1, Figure 7
  • 31
    WG2, SPM B.6.1
  • 32
    WG3, SPM C.12.1
  • 33
    WG3, SPM Figure SPM 3
  • 34
    WG3, Figure SPM 3, C.4.3
  • 35
    WG3, Chapter 6, Executive summary
  • 36
    WG3, SPM Table TS.1
  • 37
    WG3, SPM B.3.5
  • 38
    WG3, SPM B.5.2
  • 39
    WG3, SPM B.5.2, E3.3

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