IPCC Sixth Assessment Report: Impacts, adaptation and vulnerability

The Intergovernmental Panel on Climate Change (IPCC) has released the second part of its four-part, Sixth Assessment Report (AR6) in February 2022. The Working Group II (WGII) report is the most comprehensive review of climate impacts – and how much we can adapt to them – since its 2014 5th Assessment (AR5).¹ Line-by-line approval by governments as well as acceptance of the underlying scientific report ensures high credibility in both science and policy communities and ownership by governments.

The report summarises the current understanding of how climate change impacts humans and ecosystems. Compared to previous IPCC reports, WGII integrates more from economics and the social sciences and highlights more clearly the important role of social justice in adapting to climate change.

Based on publicly-available literature, this briefing covers some of the major developments in our knowledge of climate change impacts and adaptation since AR5.

1. Climate change is severely impacting people and the ecosystems we depend on

In August 2021, the IPCC published the first part of its 6th assessment report (WGI – Physical Science). WGI found that greenhouse gases from human activities had caused approximately 1.1°C of global warming by 2010-19 compared to 1850-1900, and that global temperature is expected to reach or exceed 1.5°C of warming over the next 20 years. Dubbed a “code red” for humanity by the UN’s António Guterres, the report left no space for doubt – climate change is unequivocally the result of human activities and at the current 1.1°C of global warming we are already seeing increasing impacts, including from extreme weather events such as heatwaves, droughts and flooding across the world. It also warned of abrupt responses and tipping points in the climate system (such as increased glacial melting of approximately 600 Gt of ice annually).

A Special Report on 1.5°C (SR1.5) emphasised that the world will face severe climate impacts even with 1.5°C of warming, and the effects get significantly worse with 2°C and worse still at higher levels of warming. The expectation is that WGII will pick up on explaining and outlining these risks, as recent research has shown that exceeding the 1.5°C temperature limit could lead to irreversible impacts, like the loss of species and biomes, with serious consequences, not least for food security, for humans.

Compared to the last IPCC Assessment in 2014, AR6 sees an increased focus on regional impacts, benefiting from improved models and knowledge of how global impacts manifest regionally. WGI already presented the main physical climate impacts projected for the world’s regions. For example, the African continent is already experiencing higher warming and sea level rise than the world average. In the next decade, Africa will see more frequent and intense heatwaves (up to five times more common in 2050 than today) as well as heavier precipitation, more frequent and intense droughts, and more common and severe coastal flooding. In Europe, the frequency and intensity of hot extremes is increasing, and will continue to do so, while glaciers and snow cover will continue to disappear. In North and Central America, for example, the IPCC states that tropical cyclones and heavy rainfall will become ever more frequent as the world continues to warm.²

Since AR5, more research has been done to connect the physical impacts of climate change to socio-economic and justice implications. Building on findings in the WGI report, WGII will go much further by describing the damaging impacts of climate change on humans, ecosystems and the economy, charting how climate change is disrupting livelihoods and the systems we depend on.

2. Extreme weather is causing unprecedented damage

Since the AR5 WGII report, extreme weather events that are caused or exacerbated by climate change have caused widespread and severe damage. One of the main developments in climate science since the last IPCC report has been the expansion of ‘attribution literature’. Attribution studies can tell us if, and how, climate change made a particular extreme weather event more likely or more intense. The expanded attribution literature shows that heatwaves, droughts, tropical cyclones and even locust swarms are directly linked to climate change caused by human activities.

Many of the extreme weather phenomena that the world experienced in 2021 have been attributed to human-induced climate change. The Pacific Coast heatwave in June 2021 was found to be ‘virtually impossible’ without climate change. Climate change made the massive wildfires that ripped through California and Oregon, extreme heat across the Mediterranean, and the severe flooding that Western Europe experienced much more likely. In September, the National Oceanic and Atmospheric Administration (NOAA) linked the most severe southwest USA drought in history to climate change. Meanwhile in Siberia, wildfires released about as much CO₂ as Germany produces in a year. By November, the intense rain and flooding in British Columbia, ‘made worse because of climate change’, forced 17,000 from their homes.

It is also clear that the world’s poorest and most vulnerable are at greater risk, including from mortality and other health consequences of extreme weather. Over the last decade, the mortality from floods, drought and storms has been up to 15 times higher in the most affected countries, including most of Africa and large parts of Central America, compared to less affected countries (like those located in western and northern Europe). Between 1970 and 2019, more than 91% of the deaths from weather, climate and water hazards across the world have been in developing nations. Emerging research has also found an increasing mental health burden of extreme weather. Post-traumatic stress disorders, anxiety, grief and survivor guilt are among some of the mental health challenges observed in people after extreme weather events.

Large scale human migration and displacement could be driven by more frequent resource scarcity, damage to infrastructure from extreme weather events, and increases in the frequency and severity of disease outbreaks. Human populations are concentrated in narrow climate bands, with most people living in places where the average annual temperature is about 11°C-15°C and a smaller number of people living where the average temperature is about 20°C-25°C. The climate hazard of rising temperatures alone is predicted to force 3.5 billion people to live outside the climatic zones where humans have thrived for 6,000 years. Higher temperature is projected to increase asylum applications in the EU by 28%. In 2018, the World Bank estimated that three regions (Latin America, sub-Saharan Africa, and Southeast Asia) will generate 143 million more climate migrants by 2050. The most foreseeable case of migration as a response to climate impacts will likely be the Pacific Islands. The sea level rise (at a rate of 12 millimetres per year) has already submerged eight islands in the western Pacific. Two more are on the brink of disappearing, prompting a wave of migration to larger countries. Despite this, no international agreements exist on how to protect those who are displaced and forcibly moved as a result of climate change. In 2015, a family from Kiribati applied for refugee status in New Zealand, citing climate change as the reason for the forced migration. Their application was originally denied by the New Zealand Immigration and Protection Tribunal, the Court of Appeal and the Supreme Court.

3. Impacts are getting worse, hitting marginalised people the hardest

Climate risks that negatively impact ecosystems will further limit the services these systems provide to society, and could reduce access to energy, healthcare, water and international trade. Building climate resilience is, therefore, an essential component of sustainable development, and WGII is expected to discuss the core principles of climate resilience development such as the trade-offs and synergies of sustainable development, adaptation and mitigation, and the social effects of greenhouse gas emissions. Research has shown that human-induced climate change could occur across 80% of the world’s land area, where 85% of the population reside. These impacts will propagate across national boundaries through global supply chains, which are increasingly compromised by climate impacts. In the US, the annual costs to supply chains from natural disasters rose to a record high of USD 95 billion in 2020. These costs will continue to grow. For example, McKinsey predicts that a collapse in the global supply of semiconductors (critical to the global tech industry) from a hurricane will grow up to four times by 2040 due to climate change.

Food production systems are also under increasing pressure. Human activities have already changed 75% of the Earth’s land, and nearly 75% of freshwater resources are now devoted to crop or livestock production. Today, 25% of the total land area of the world is degraded. Land degradation has reduced the productivity of 23% of the global land surface, with global agriculture crop production increasing by 300% since the 1970s. The IPCC’s Special Report on Land (SRCCL) estimated that soil erosion from agricultural fields is 10 to 20 times (no tillage) to more than 100 times (conventional tillage) higher than the soil formation rate. Scientists have warned 24 billion tons of fertile soil are lost each year, largely due to unsustainable agriculture practices. If this trend continues, 95% of the Earth’s land areas could become degraded by 2050. Studies that separate out the effects of climate change alone have shown that yields of some crops (like maize and wheat) in many lower-latitude regions have declined. Increasing temperatures will continue to impact food production, estimating up to a 29% increase in the cost of cereals by 2050, depending on the amount of warming. These price increases will impact consumers globally, with low-income consumers at particular risk of malnutrition.

As a result of climate change and land degradation, one million animal and plant species are now threatened with extinction, many within decades – more than at any time in human history, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). Today, only 15% of land and just under 8% of the ocean are under some form of ecosystem protection. IPBES concludes that the loss of ecosystems has made human communities more vulnerable to climate impacts. Continued overlapping climate change with non-climatic pressures like land-use change, deforestation, infrastructure development, resource extraction, overfishing and pollution will continue to threaten ecosystems and people’s livelihoods. Climate change currently affects at least 10,967 species on the International Union for Conservation of Nature (IUCN)’s Red List of Threatened Species. The Bramble Cay melomys (a genus of rodents) is the first mammal reported to have gone extinct as a direct result of climate change.

Since AR5, more research has shown that the most marginalised, both economically and socially, are hit first and hardest by climate impacts, both in the global south and north. Climate change could cause GDP losses of 64% in the world’s most vulnerable countries, and the impacts of climate change may further exacerbate marginalisation and injustices. On a global scale, new research shows the vulnerabilities of the urban poor. According to one study, if greenhouse gases continue on their current trajectory, 215 million urban poor around the world will be exposed to average summer temperatures of over 35°C – an eightfold rise from today – which will increase the risks of heat mortality.

Worryingly, scientists say that ‘compound extremes’ will become more common in a warming world, and that these events are likely to cause more suffering than we would see from individual events alone. Compound extremes arise when multiple climate hazards (such as extreme temperature and precipitation) occur simultaneously in the same place, affect multiple regions at the same time, or occur in a sequence (commonly referred to as cascading events). Climate hazards can be also compounded by other human impacts, such as pollution, habitat fragmentation and environmental degradation. For example, the rise in concurrent drought and heatwave events was especially observed in southern and central Africa over the last decade, and the impact of these compound events can last longer as a result of climate change.³ An initial rise in temperature can trigger a cascade of climate impacts. For example, sustained higher temperatures that decrease in soil moisture will suppress plant growth, which in turn suppresses rainfall, leading to more drought in what is known as an escalating ‘feedback loop’. In recent years in California, a combination of droughts and heatwaves have led to wildfires and in some cases, been followed by heavy rain and landslides.

Academic literature exploring the complex connections between climate change, extreme weather, migration and conflict has also expanded. The civil war in the Darfur region of Sudan is an example of a conflict researchers think was made worse, or even triggered, by a changing climate. In 1983-84, a drought fuelled a famine that killed over 100,000 people and led to mass ecological migration, mainly towards southern Darfur. As people migrated into different regions, ethnic polarisation disrupted regional harmony and triggered conflict. Migration is a complex topic, which cannot be simply attributed to one cause. However, researchers have focused on the increased risks of migration that small island states and coastal cities will face due to climate change. One estimate suggests that between 17 million and 72 million people may have to relocate from coastal settlements if sea levels rise somewhere between 0.3 and 1.7 metres.

4. Adaptation is vital, but far more is needed

Since AR5, there has been an increase in adaptation activities, including by governments, businesses and civil society, with most in response to extreme weather events. For example, an EU Commission-funded project by the WHO and the London School of Tropical Medicine charts the need to shift from disaster response to risk management for flooding in Europe, including better warning systems and health protection measures. However, though adaptation options are available across all sectors and can reduce the risks of climate change, adaptation has so far been dominated by small changes to current systems, rather than the transformative changes that experts say we needed.

Adaptation and biodiversity are closely linked and implementing nature-based solutions (NbS) can create co-benefits for adaptation to climate change, for nature and its contribution to people. However, trade-offs can arise if climate mitigation policy encourages NbS with low biodiversity value, such as afforestation with non-native monocultures. In 2021, the IPBES and IPCC found that the “mutual reinforcing of climate change and biodiversity loss means that satisfactorily resolving either issue requires consideration of the other.” One of the best documented co-benefits of adaptation is the positive impact on population health, both physical and mental, when investing in nature-based and green infrastructure in cities. Similarly, scientists found that global mangroves are responsible for storing a stock of 6 billion tonnes of carbon, and that restoring mangroves protects against flooding and is two-to five-times cheaper than conventional engineered sea level rise protection. As a result, several nations, including Indonesia, India, Bangladesh and Sri Lanka, are investing in mangrove restoration for adaptation.

Scientists have made significant progress in estimating the costs of climate change impacts, finding that adaptation can be cost effective if it is done in a timely manner. The upcoming IPCC report is likely to reflect that, although numbers still vary widely, the costs of impacts are now thought to be much higher than AR5 suggested. Yet despite the benefits to adaptation (and the threat of tipping points), currently most climate finance is directed to mitigation and there remains a large finance gap (public and private) between the amount of money flowing to developing countries and the amount needed. Estimated adaptation costs in developing countries are five to 10 times greater than current public adaptation finance, and the adaptation finance deficit grows at higher levels of warming. It is expected that the WGII report will discuss some of the fundamental barriers to access private finance for adaptation, such as the fact that private investment tends to gravitate to opportunities where revenues are highest and risks are lowest, meaning it is unlikely to target the most vulnerable developing nations or non-market sectors, where adaptation is needed the most.

Although adaptation is a necessary solution to the climate impacts we are already experiencing, previous IPCC reports have also emphasised the limitations of adaptation. The Paris Agreement refers to impacts of climate change that have not been, or cannot be, avoided through mitigation and adaptation and that are considered the third pillar of climate action. The AR5 WGII report discussed the losses and damages associated with ‘hard’ (biophysical, institutional, financial, social and cultural) and ‘soft’ (technological and socioeconomic) limits to adaptation. For example, there are hard physical limits to how much Small Island Developing States (SIDS) can adapt to rising sea levels, and their vulnerability to climate change is likely to lead to forced migration from these countries. For species and ecosystems, there may be hard limits to the physiological capacity of individual organisms to adapt to changes in the climate. Often, socioeconomic barriers stop the poorest and most vulnerable people from being able to adapt. The SR1.5 built upon these definitions and assessed the soft and hard adaptation barriers for impacts under a 1.5°C and 2°C of global warming, and we expect the issue of equity and justice in responding L&D to be the focus of the upcoming AR6 report.

5. The costs of inaction far exceed those of mitigation and adaptation

The need for, and success of, adaptation is closely linked to the level of mitigation we achieve. The AR5 WGII report highlighted that the overall risks of impacts can be reduced by limiting the rate and magnitude of climate change, which will in turn reduce the scale of adaptation required. Studies have found per capita GDP would be 5% higher by 2100 if temperatures are stabilised at 1.5°C above pre-industrial temperatures rather than 2°C and limiting global warming to 2°C instead of 4°C could save USD 17.5 trillion a year globally by 2100. Conversely, the cost of failing to limit warming to 1.5°C rises dramatically – from USD 1.3 trillion a year of inaction in 2010 to over USD 5 trillion a year in 2020.

Adaptation is already necessary and will be harder or impossible with greater warming. The economic damage that climate change and extreme weather events cause is already significant: The cost of climate impacts in Central America in 2010 ranged from 2.9% of GDP for Guatemala to 7.7% for Belize; Tropical Cyclone Pam caused loss and damage to Vanuatu’s agricultural sector estimated at 64.1% of GDP in 2015; while Hurricane Maria caused loss and damage totalling 224% of Dominica’s GDP in 2016. Nearly half the global population is already living in potential water-scarce areas at least one month a year and this could increase to some 4.8 billion – 5.7 billion by 2050.

The WGII report discusses how a delay in mitigation and adaptation actions will threaten sustainable development, as climate change impacts and responses are closely linked to social well-being, economic prosperity and environmental protection. Human-induced climate change may lead to a decline in agricultural yields, water scarcity, food insecurities, reduced livelihoods and displacement of communities, and the impacts will not be felt equally by all. Climate change is projected to increase the number of people experiencing extreme poverty from 32 million to 132 million by 2030. The gap between the economic output of the world’s richest and poorest countries is 25% larger today than it would have been without global warming. If climate change is not addressed through global reduction in emissions, global income inequality is predicted to widen as a result of decreases in global incomes.

6. Further reading: Explainers and scientific papers

The list below summarises some important commentaries and scientific papers, focusing on those published in the last two years. It is not a comprehensive review of the scientific literature. To explore the specific topics further, please refer to the reference lists within these publications.