In-depth Q&A: The IPCC’s sixth assessment on how climate change impacts the world

The threat that climate change poses to human well-being and the health of the planet is “unequivocal”, says the latest report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC).

The expansive review – which forms the second part of the IPCC’s sixth assessment report (AR6) – warns that any further delay in global action to slow climate change and adapt to its impacts “will miss a brief and rapidly closing window of opportunity to secure a liveable and sustainable future for all”.

The report follows the publication of the first part of AR6, released in August last year, which set out how and why the Earth’s climate is changing. 

Over the past two weeks, government delegations have been meeting during a two-week online approval session to agree on the high-level “summary for policymakers” section. 

The final report is published against the backdrop of Russia’s invasion of Ukraine, which forced some members of the Ukrainian delegation to pull out of the approval session and hide in bomb shelters. One member commented that “we will not surrender in Ukraine and we hope the world will not surrender in building a climate resilient future”.

Focusing on the impacts of global warming and efforts to adapt to it, the report lays bare how climate change is being felt across the planet. Among the findings, the report concludes that:

• Climate change has already caused “substantial damages and increasingly irreversible losses, in terrestrial, freshwater and coastal and open ocean marine ecosystems”.
• It is likely that the proportion of all terrestrial and freshwater species “at very high risk of extinction will reach 9% (maximum 14%) at 1.5C”. This rises to 10% (18%) at 2C and 12% (29%) at 3C.
• Approximately 3.3 to 3.6 billion people “live in contexts that are highly vulnerable to climate change”.
• Where climate change impacts intersect with areas of high vulnerability, it is “contributing to humanitarian crises” and “increasingly driving displacement in all regions, with small island states disproportionately affected”.
• Increasing weather and climate extreme events “have exposed millions of people to acute food insecurity and reduced water security”, with the most significant impacts seen in parts of Africa, Asia, Central and South America, small islands and the Arctic.
• Approximately 50-75% of the global population could be exposed to periods of “life-threatening climatic conditions” due to extreme heat and humidity by 2100.
• Climate change “will increasingly put pressure on food production and access, especially in vulnerable regions, undermining food security and nutrition”.
• Climate change and extreme weather events “will significantly increase ill health and premature deaths from the near- to long-term”.

The report warns that if global warming passes 1.5C – even if overshooting that global average temperature temporarily before falling back again – “human and natural systems will face additional severe risks”, including some that are “irreversible”.

In response to these impacts, adaptation efforts “have been observed across all sectors and regions, generating multiple benefits”, the authors say, but this progress is “unevenly distributed” as well as being “fragmented, small in scale [and] incremental”.

As a result, “gaps exist between current levels of adaptation and levels needed to respond to impacts and reduce climate risks”, the report warns.

These gaps are “partially driven by widening disparities between the estimated costs of adaptation and documented finance allocated to adaptation”, the authors say, adding that the “overwhelming majority” of global climate finance has so far been targeted at climate change mitigation.

Commenting on the report, UN secretary-general António Guterres described it as “an atlas of human suffering and a damning indictment of failed climate leadership”.

Calling on all G20 governments to “dismantle their coal fleets”, Guterres warned that “as current events make all too clear, our continued reliance on fossil fuels makes the global economy and energy security vulnerable to geopolitical shocks and crises”.

In the in-depth Q&A below, Carbon Brief unpacks the key findings of the report and the developments since the IPCC’s last assessment. Please use the links to navigate between the sections.

1. What is this report?
2. How is climate change affecting land and freshwater ecosystems?
3. What impact is global warming having on marine life?
4. How is climate change affecting the world’s water?
5. What does the report say about impacts on food and agriculture?
6. What risks does climate change pose to the world’s cities?
7. What does the report say about public health, conflict and migration?
8. How does climate change affect poverty and progress towards the sustainable development goals?
9. How is the world adapting to climate change?
10. Are there limits to what adaptation can achieve?
11. What does the report say about ‘loss and damage’?
12. What are the risks of ‘maladaptation’ and the unintended consequences of tackling climate change?
13. What role can nature-based solutions play in adaptation and mitigation?
14. What does the report say about climate-resilient development?
15. What information about specific regions does the report contain?

1. What is the Working Group II report?

The new report is part of the IPCC’s latest assessment cycle – the sixth set of “assessment reports” since its foundation in 1988. The previous set – the fifth assessment report (“AR5”) – was published in 2013-14. (See Carbon Brief’s coverage here.) 

As usual, the IPCC’s efforts for AR6 are divided into three “working groups”:

• Working Group I (WG1): The physical science basis
• Working Group II (WG2): Impacts, adaptation and vulnerability
• Working Group III (WG3): Mitigation of climate change

Back in September 2017, the IPCC agreed outlines for all three working groups. And in April 2018, the IPCC announced the authors who had been selected – more than 700 in total, who all work on a voluntary basis.

The WG2 report is the second of these to be published, following the WG1 report in August 2021. The WG3 report is expected to be published in March or April this year, followed by a synthesis report in September.

Originally intended to be published in October 2021, the publication date was pushed back due to the disruption caused by the Covid-19 pandemic. 

It is also worth noting that the IPCC does not only publish full assessment reports. The sixth assessment cycle has also included shorter “special reports” on three topics:

• Global warming of 1.5C (“SR15”) in 2018
• Climate change and land (“SRCCL”) in 2019
• The ocean and cryosphere in a changing climate (“SROCC”) in 2019

(In addition, the IPCC has published a 2019 “methodology report” on guidelines for national greenhouse gas inventories.)

The IPCC’s mandate “involves the provisioning of available scientific information and evidence to inform climate action by multiple actors, notably governments (including international alliances) in the context of the UN Framework Convention on Climate Change”, the report says.

Specifically, the aim of the WG2 report is to address “the challenges of climate action in the context of sustainable development with a particular focus on climate change impacts, adaptation and vulnerability”, the authors write.

The report includes 18 chapters – seven of which are dedicated to the continents, with “small islands” replacing Antarctica. Along with seven “cross-chapter papers” that focus on topics such as “biodiversity hotspots” and “polar regions”, these chapters comprise the “regions” section of the report. In total, the report runs to more than 3,000 pages.

In contrast to previous assessments, the authors say that the new report “embeds adaptation in each regional and sectoral chapter rather than in separate adaptation chapters, in order to reflect the increasing prevalence of adaptation and the extent to which many current risk, impacts and vulnerability estimates incorporate adaptation actions already taken”.

Over the course of the report-writing process, three drafts have been reviewed by numerous experts and governments. For example, the authors have addressed more than 16,000 comments and more than 40,000 comments on the first and second drafts, respectively.

With the main report complete, the final step has been a line-by-line agreement of the short summary for policymakers (SPM) document by government delegates. This approval meeting has been carried out virtually over the past two weeks. Scheduled to finish on Friday 25 February, the session overran before the SPM and underlying report were formally accepted on Sunday morning.

In keeping with AR6 WG1, the WG2 report uses the output from the latest generation of global climate models, produced as part of the sixth Coupled Model Intercomparison Project (CMIP6). These coordinated efforts consist of “runs” from around 100 distinct climate models being produced by dozens of different modelling groups around the world. Specifically, WG2 uses the “assessed warming” projections developed for WG1, which take into account “multiple lines of evidence” in addition to climate model output. (This is explained in more detail in Carbon Brief’s coverage of the WG1 report.)

The report also uses output from CMIP5, used extensively in AR5 and since, the SPM says:

“Climate impacts literature is based primarily on climate projections assessed in AR5 or earlier, or assumed global warming levels, though some recent impacts literature uses newer projections based on the CMIP6 exercise”.

The WG2 report also uses the same set of five Shared Socioeconomic Pathways (SSPs) as WG1. These describe broad narratives of future socioeconomic development and are paired with scenarios of future energy use and greenhouse gas emissions. They are named according to approximate radiative forcing levels each one entails at the end of the 21st century.

(Read Carbon Brief’s in-depth explainer on the SSPs.)

The figure below – from the WG1 report – illustrates how the SSPs (columns) combine with the forcing levels (rows) – note that not all forcing levels are possible under each socioeconomic pathway. The figure also shows the “Representative Concentration Pathways” (RCPs), which were used in AR5 and are not directly comparable with the SSPs.

The final SSPs in white lettering indicate the core set of five SSP scenarios, which spans “a wide range of plausible societal and climatic futures from potentially below 1.5C best-estimate warming to over 4C warming by 2100”, the WG1 report says:

• SSP1-1.9: ​Holds warming to approximately 1.5C above 1850-1900 in 2100 “after slight overshoot” and implied net-zero CO2 emissions around the middle of the century.
• SSP1-2.6: Stays below 2C warming with implied net-zero emissions in the second half of the century.
• SSP2-4.5: Approximately in line with the upper end of combined pledges under the Paris Agreement. The scenario “deviates mildly from a ‘no-additional climate-policy’ reference scenario, resulting in a best-estimate warming around 2.7C by the end of the 21st century”.
• SSP3-7.0: A medium-to-high reference scenario resulting from no additional climate policy, with “particularly high non-CO2 emissions, including high aerosols emissions”.
• SSP5-8.5: A high reference scenario with no additional climate policy.

The WG2 report follows the same set of “calibrated language” that AR5 used to communicate levels of certainty behind the statements it included. These terms fall into two categories:

• “Confidence reflects qualitative judgments of the validity of findings. It thereby facilitates, more readily, comparisons across assessment conclusions. Increasing evidence and agreement corresponds to increasing confidence.”
• “If uncertainties can be quantified, the framework involves a further option of characterising assessment findings with likelihood terms or more precise presentations of probability…Probabilistic judgments can be based on statistical or modelling analyses, elicitation of expert views, or other quantitative analyses…Usually, likelihood assignments are underpinned by high or very high confidence in the findings.”

These statements of confidence and likelihood – listed in the figure below – are shown in italics in the report and in this article, too.

For example, the opening chapter of the report says – with high confidence – that “since IPCC AR5, human influence on the Earth’s climate has become unequivocal, increasingly apparent, and widespread, reflected in both the growing scientific literature and in the perception and experiences of people worldwide”.

Equally, where the report offers statements of fact, these do not require calibrated language. For example, the authors note that “limiting atmospheric greenhouse gas concentrations reduces climate-related hazards while adaptation and sustainable development reduce exposure and vulnerability to those hazards”. 

As a result, the authors say, “implementing adaptation and mitigation actions together with Sustainable Development Goals (SDGs) helps to exploit synergies, reduce trade-offs and makes all three more effective”.

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2. How is climate change affecting land and freshwater ecosystems?

Climate change has caused “substantial damages and increasing irreversible losses to land ecosystems across every region of the world, the report says.

The extent and magnitude of climate impacts on the natural world is “larger than estimated in previous [IPCC] assessments”.

Evidence suggests it is very likely that changes to the geographic ranges, physiology and morphology of land species can be attributed to climate change, the report says. Climate change is also very likely to have had an effect on animal “phenology” – the timing of key life events.

Half of all land species studied have shifted their geographic ranges in response to “regional climate changes”, the report says.

The movement of species globally is “altering the make-up” of ecosystems and “potentially” allowing the increased spread of invasive species, the report says with medium confidence.

The report says that climate change has increased wildlife diseases. Temperature rise and more brutal extreme weather events have played a role in the emergence of new diseases in new areas, according to experimental studies. 

In countries close to the Arctic, there is evidence that climate change has helped vector-borne diseases that infect humans to expand, it adds.

Meanwhile, forest insect pests are causing greater damage in northern North America, Europe and Asia due to “warmer winters reducing mortality and longer growing seasons favouring more generations per year”.

(Read Carbon Brief’s Q&A on how climate change and biodiversity loss is changing the risk of pandemics.)

Climate change could have played a role in the extinction or near-extinction of at least three species, the report says.

It says with high confidence that climate change played a role in the extinction in the wild of the white ringtail possum in Australia and the Bramble Cays Melomys – a rat that was endemic to a vegetated coral mound at the northern tip of the Great Barrier Reef. It adds with medium confidence that climate change drove the extinction of the cloud-forest-restricted Golden toad in Costa Rica.

A study of 976 plants and animals found that 47% had suffered local extinctions as a result of climate-induced changes, the report adds.

Since the last IPCC AR5 WG2 report was published in 2014, there has been an increasing number of biome shifts and structural changes within ecosystems, the report says.

“New studies are documenting the changes that were projected in prior reports,” the IPCC says. This includes upward shifts to alpine and boreal forests and more trees in the sub-Arctic tundra.

A combination of climate change, shifts to grazing and fire management is causing trees to encroach further into grasslands and savannahs, the report adds.

A quarter of the world’s natural land now sees longer fire seasons as a result of increases in temperature, aridity and drought, according to the findings. 

Evidence shows human-caused climate change has contributed to a doubling of area burned by wildfires across the western US since the 1980s.

Forest area burned by wildfires has also increased in the Amazon, the Arctic, Australia and parts of Africa and Asia. However, these increases have not formally been linked to climate change, the report says. (Read Carbon Brief’s in-depth explainer on the links between climate change and wildfires.)

In addition, climate change is causing mass tree die-offs through its impact on droughts. It has potentially contributed to 100 cases of drought-induced tree die-off across Africa, Asia, Australia, Europe and the Americas, according to the assessment.

Despite humanity’s impact on land, it still stores more carbon than it emits each year, the report says. The land currently stores around 3.5tn tonnes of carbon, three-to-five times more than the amount stored by unextracted fossil fuels and four times more than what is currently in the atmosphere.

However, future climate change threatens the very “fundamental aspects” of land ecosystems, the report says. 

The IPCC’s “burning embers” chart below illustrates how the severity of key risks associated with land (and water) ecosystems could change at different levels of warming.

On the chart, purple indicates a very high probability of severe impacts or risks, red signifies significant and widespread impacts or risks, yellow indicates detectable risks and white shows no detectable risks.

Black dots indicate the level of confidence in the findings, from very high (four dots) and high (three dots) to medium (two dots) and low (one dot).

It is likely that the proportion of all species at very high risk of extinction (categorised as “critically endangered” by the IUCN Red List) will reach 9% (maximum 14%) at 1.5C, 10% (18%) at 2C, 12% (29%) at 3C, 13% (39%) at 4C and 15% (48%) at 5C, the report says.

Insects (particularly pollinators), amphibians and flowers face the biggest extinction risks at “mid-levels of warming” (3.2C), it adds.

“Loss of species reduces the ability of an ecosystem to provide services and lowers its resilience to climate change,” the authors say.

The report notes, with medium confidence, that “more frequent and intense extreme events, superimposed on long-term climate trends, have pushed sensitive species and ecosystems towards tipping points, beyond ecological and evolutionary capacity to adapt, causing abrupt and possibly irreversible changes”.

Looking to the future, a scenario where temperature rise temporarily exceeds 1.5C for several decades before returning to below this warming level could push many species past their “physiological tolerance limit”, the report says.

“These changes may lead to collapse or transition of ecosystems to a new ecological state with a loss or altered biodiversity, including species extinctions, and loss of ecosystem services,” it adds.

At 4C of global warming, more than a third (35%) of the global land surface could witness biome shifts, the report says. This could be limited to less than 15% if temperatures are kept below 2C. 

This level of warming could see large swathes of the Amazon rainforest shift to drier, less dense vegetation, further poleward shifts of boreal forests into the Arctic tundra and upslope shifts of mountain forests into alpine grasslands, the report says.

If an area is at risk of land-use change as well as climate change, the risk of biome shift can be twice or three times greater, it adds.

(For more on tipping points, see Carbon Brief’s in-depth explainer.)

A global temperature rise of 4C could also see net global wildfire frequency increase by 30%, the report says with medium confidence. 

The impact of climate change on ecosystems could “substantially” increase the release of land carbon in the atmosphere, prompting “self-reinforcing” feedback loops. “The exact timing and magnitude of climate-biosphere feedbacks and potential tipping points of carbon loss are characterised by large uncertainty,” the report says.

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3. What impact is global warming having on marine life?

Previous IPCC reports have found, with “growing confidence”, that humanity’s emissions are impacting the oceans and their ecosystems. In the time since the last assessment report, more research – including observational work, modelling studies, palaeoclimate proxies and Indigenous knowledge – has “provide[d] increasing evidence” of climate change’s impacts on marine ecosystems, the new report says.

The report states with very high confidence that human-driven chemical and physical changes to the ocean are altering the distribution and abundance of marine organisms “from microbes to mammals and from individuals to ecosystems, in every region” of the world. It also says with high confidence that “climate change has exposed ocean and coastal ecosystems to conditions that are unprecedented over millennia”.

As the oceans warm, marine species are being forced out of their natural habitats, “generally follow[ing] the pace and direction of climate warming”. Since the 1950s, these poleward shifts are happening at a rate of almost 60km per decade – although the report notes that there is “substantial variation” in this rate, depending on the species and region.

While there is high confidence that fish and marine mammals are being pushed poleward by warming waters, there is low-to-medium confidence that species’ distributions are shifting deeper in the ocean in response. 

Warming is also affecting the timing of key biological events, such as phytoplankton blooms, commercial fish spawning and marine reptile breeding, the authors say. Nearly three-quarters of published studies are “consistent” with these changes, although the report notes there is a significant northern-hemisphere bias, with more than 95% of observations recorded there.

In many cases, warming exacerbates the effects of other stressors that organisms may be experiencing. The report divides these into “climate-induced drivers” and “non-climate drivers”. Other climate drivers include ocean acidification and deoxygenation, while non-climate drivers include pollution, overfishing, invasive species and habitat degradation. 

The chart below shows observed changes in the ocean between 1925-2016: warming rate (top), climate velocity – the speed and direction that a given point on a map would need to move to maintain its current climate state – (middle) and the change in total number of marine heatwave days, calculated as the difference between the time periods 1925-54 and 1987-2016 (bottom). Darker colours show stronger positive (red) and negative (blue) effects.

The report notes that organisms “frequently experience” climate and non-climate drivers at the same time. As a result, disentangling the effects of climate change and other non-climate drivers is difficult.

The observational records of many marine ecosystems are short, or have a geographic bias, which also contributes to the challenge of attribution. However, a “growing body” of work “increasingly provides multiple lines of evidence” for attributing these impacts to climate change, the authors say.

The report notes a “wide range of responses” of commercially exploited fish and invertebrate species to warming, the majority of which have been “detrimental”. However, overexploitation of fisheries also has a significant impact on fishery yields, and these “combined effects…make it difficult to assess” what portion of this comes from climate change.

There are some cases where attribution is more clear than in others. For example, climate change is exacerbating the magnitude, extent and frequency of marine heatwaves – as it is with many other types of extreme weather.

There is high confidence that marine heatwaves can lead to “mass mortality” events among “key foundational species”. In “most regions”, seaweeds such as kelp are already experiencing such mass mortality events, along with range shifts. This is partially due to the direct effects of warming and partially due to indirect effects, such as changing ranges of plant-eating species. 

The report warns of “irreversible phase shifts” in these ecosystems if 1.5C warming is surpassed and that they are at “high risk”, even if warming is kept to below 1.5C with periods of “temperature overshoot” above that threshold.

The report projects with medium confidence that even under SSP1-1.9, mangroves and saltmarshes are likely at “high risk” from future sea-level rise, “with impacts manifesting in the mid-term”.

Coral reefs, which are home to one-quarter of marine biodiversity, face a range of threats from both climate and non-climate drivers. Increasingly frequent and severe heat stress have increased both mass bleaching events and disease outbreaks. There is high confidence that  with warming above 1.5C, reefs are “under threat” of reaching erosion rates that are larger than the rate at which new corals can grow.

Ocean acidification is also decreasing both coral cover and diversity; these effects can be “exacerbate[d]” by warming, although some evidence suggests that these responses differ between species. Other calcifying organisms, such as mussels and oysters, are also at “high risk of decline” due to a combination of climate stressors, the report warns.

There is medium confidence that continued warming, acidification and sea level rise will increase the risk of both regional and global extinctions of certain species – even if warming is limited to less than 2C by the end of the century.

Another major climate driver is hypoxia, or low oceanic oxygen levels. Hypoxia is caused by the decreased solubility of oxygen in warmer waters as well as increased respiration rates of marine microbes and changes in the circulation of the ocean.

The report states that low-oxygen zones are increasing in both size and number around the world “with growing impacts on fish species diversity and ecosystem functioning”. Declining oceanic oxygen levels “have already decreased suitable habitat” for important open-water fish species such as tuna by 15%. There is medium confidence that the subsurface ocean will see “historically unprecedented” low levels of oxygen over the remainder of this century. 

Organisms whose habitats are more “thermally stable”, such as the polar regions or the deep sea, “are often more sensitive to warming” than those from environments with more temperature variation, the authors say. The report states with high confidence that warming has contributed to “major community shifts, both gradual and abrupt” in fish, marine mammals and seabirds in the polar regions. 

The report also notes that organisms in certain life stages – such as eggs and embryos – are less tolerant to heat than adult organisms.

Many organisms’ responses to stressors are affected by the availability of food. Thus, the report states, “studies conducted under an excess of food risk underestimating the ecological effects of climate-induced drivers”.

The chart below shows a summary of the impacts of different climate drivers on a range of oceanic ecosystems, as well as their capacity to adapt to change. The colours show the strength of the impact, with darker colours indicating stronger impacts; the dots in each box show the confidence level from low confidence (one dot) to high (three dots).

Evolution can provide one avenue for relief from the changing climate. Experimental evidence has shown that microbial populations can adapt to conditions mimicking those of climate change on rapid timescales. 

However, research into the ability of “complex and long-lived” organisms to evolve and adapt to climate change remains a “major gap”, the report says. And the longevity of marine birds and mammals “suggests limited evolutionary resilience to rapid climate change”. 

Looking more broadly, ecosystem models are a useful way of understanding potential future outcomes of a changing climate. But, the report states, they “cannot be expected to accurately project the trajectories of complex marine ecosystems”. 

Both CMIP5 and CMIP6 ensembles project declines in global net primary production – the net carbon gained by phytoplankton and other plants in the ocean – by 2080-99 as compared to 1996-2015 levels, but CMIP6 shows much smaller decreases, and there is low confidence in this projection due to regional variations and uncertainties in the underlying drivers.

Global models also project a loss in marine biomass (the total weight of all animal and plant life in the ocean) of around -6% (±4%) under SSP1-2.6 by 2080-99, relative to 1995-2014. Under SSP5-8.5, this rises to a -16% (±9%) decline. In both cases, there is “significant regional variation” in both the magnitude of the change and the associated uncertainties, the report says.

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4. How is climate change affecting the world’s water?

The fourth chapter of the report is dedicated to how climate change is affecting water.

At present, roughly half of the world’s human population experiences severe water scarcity for at least one month per year, the report estimates with medium confidence.

And, since the 1970s, 44% of all “disaster events” on Earth have been flood-related, the report says. (The IPCC says “disasters” involve extreme weather events “coupled with high vulnerability and exposure” in human populations.)

Nearly half a billion people live in “unfamiliarly wet areas” – where long-term average rainfall is high as previously seen in only one in six years – while 163 million people live in “unfamiliarly dry areas”, the report estimates.

Heavy rainfall intensity has increased in “many regions” since the 1950s. Around 700 million people live in regions where maximum daily rainfall has increased, the report estimates.

In the northern hemisphere, snow cover across all months of the year is decreasing, the report says. Snow cover extent peaked in the northern hemisphere from the 1950s to 1970s, the report says, and has been in decline ever since.

Over the past two decades, the loss of ice from glaciers – frozen freshwater rivers found in high latitudes – has exceeded 0.5 metres of water equivalent each year. (Water equivalent represents the volume of water created from melting the ice.) This is higher than at any other time since records began.

The map below shows changes to glaciers across the world from 2000 to 2019.

The figure shows changes to glacier elevation (green bars; in metres per year); “mass balance”, a measure of the total amount of ice held by glacier once summer melting and winter recovery have been taken into account (blue bars; in metres of water equivalent per year); and mass change (in billions of tonnes per year).

The figure shows that glacier mass change rate has been highest in the western US and Canada, Iceland and Svalbard, a Norwegian archipelago located between mainland Norway and the North Pole. 

The melting of glaciers is impacting “humans and ecosystems”, including “vulnerable high mountain and polar communities”, the report says.

It cites a study finding changing ice conditions in the Canadian Arctic have affected access to trails for Inuit communities. It also cites a US federal report finding the melting of ice has affected Alaskan Native populations’ access to culturally-significant species.

The report also says there is a “knowledge gap” in how ice-related floods, including glacier-related and ice-jam floods, are responding to ongoing climate change.

There is a “clear trend” of increases to streamflow in rivers in the northern high latitudes, the report says with high confidence.

Meanwhile changes to groundwater stores, which are relied upon by billions of people for water, are less straightforward, according to the findings.

For example, the report notes that groundwater storage has declined in many parts of the world since the start of the 21st century, largely due to a growing demand for water for crop irrigation.

In higher altitudes, warming has altered groundwater levels, which may have played a role in reduced spring-time recharge, it adds.

It is very likely that human-caused climate change affected global patterns of soil moisture over the 20th century, the report says, with consequences for agriculture, ecosystems and the severity of extreme weather events.

Human-caused climate change has also made floods and droughts more likely and more severe. 

Between 1970 and 2019, 7% of all “disaster events” were drought-related. However, drought disasters accounted for 34% of disaster deaths, particularly in Africa.

Meanwhile, severe rains made more likely by climate change have caused catastrophic flooding in areas such as western Europe, China, Japan, the US, Peru and Brazil since 2014.

Changes in these water-related hazards “disproportionately impact vulnerable populations such as the poor, women, children, Indigenous peoples and the elderly in all locations”, the report warns.

Changes to the water cycle are impacting agriculture, the report explains. Between 1983 and 2009, around three-quarters of the global harvested area experienced yield losses because of drought, costing the world an estimated US$166bn, the report says.

In the future, “water-related risks are projected to increase with every degree of global warming”, the report says.

At 2C of global warming, 3 billion people could face water scarcity, the report says with medium confidence. At 4C, this figure rises to 4 billion.

Under a scenario where greenhouse gas emissions do not peak until 2060 (“RCP6.0”), roughly 1.5 billion people who “critically depend” on run-off from mountains for freshwater could face negative impacts.

Every fraction of temperature rise will also worsen drought and flood risk, the report says.

Under RCP6.0 and SSP2, the global population exposed to “extreme-to-exceptional” drought could increase from 3% to 8% over the 21st century.

Extreme agricultural drought across large areas of North and South America, the Mediterranean and Eurasia is projected to be twice as likely at 1.5C, 150-200% more likely at 2C and over 200% more likely at 4C, when compared to current conditions.

Risks to agricultural yields from temperature and water changes could be three times higher at 3C rather than 2C, the report says with medium confidence.

Projected increases in rainfall intensity will cause more flooding, the report says.

Direct flood damages could be four to five times higher if global warming reaches 4C rather than 1.5C, the report says. In addition, GDP losses related to flooding could be 1.2-1.8 times higher if warming reaches 2C rather than 1.5C, the authors say, with medium confidence.

The maps below show projected changes to global river flooding by the 2080s under a low (SSP1-2.6), medium (SSP2-4.5) and high (SSP5-8.5) scenario. On the chart, blue shows increases in flood frequency while red indicates decreases. Dots illustrate results where there is high agreement between climate models.

At 4C of global warming, around 10% of the global land area, supporting 2.1 billion people, could face increases in extreme streamflow, the report says.

Meanwhile, some parts of Europe, including the Mediterranean, could see the potential for hydropower decrease by 40% at 3C, compared to 10% at 2C and 5% at 1.5C, the report adds.

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5. What does the IPCC report say about impacts on food and agriculture?

Climate change is “increasingly hindering efforts” to meet the nutritional and calorific needs of humanity, according to the new report.

Climate change impacts – including weather extremes, such as droughts, floods and marine heatwaves – are putting strain on agriculture, aquaculture, forestry and fisheries. Each step in the supply chain from production to consumption, including storage and transportation, will also be affected by climate change.

The report finds medium evidence, but high agreement that “sudden food production losses” due to extreme events have been increasingly frequent “since at least [the] mid-20th century”. 

There is high confidence that extreme weather events will push some current food-growing areas “beyond the safe climatic space for production”. Under the very high emissions scenario SSP5-8.5, about one-third of “currently suitable area” is projected to become unsuitable by the end of the century; the report notes that these impacts “will be much less under RCP2.6”.

The CMIP6 suite of models and the latest generation of crop models, which simulate how crops will respond to changing environmental conditions, project that climate change will affect the yields of major crops “sooner than previously anticipated”. This is attributed to both “warmer climate projections and improved crop model sensitivities”.

A temperature rise of 2C by the end of the century will have “large negative impacts” on food production systems around the world, the report says, while higher temperatures will pose “even greater risk”. Land that is currently used for growing crops and rearing livestock “will increasingly become climatically unsuitable”, while outdoor workers and animals will be “increasingly expose[d]” to dangerous heat stress.

Crops are negatively affected by climate change in several ways. One study cited in the report estimated nearly a 10% yield reduction in four major crops between 1850 and 2010, even when taking into account the “positive effect” of CO2 fertilisation. 

The chart below shows how five climate change impacts – changing soil nutrients, increased pests and disease, decreased rainfall, increased ozone stress and increased heat stress – will impact soya (left) and wheat (right) yields around the world. The shading indicates the stress level of a given impact, with darker colours meaning a higher level of stress.

In addition to the threat of yield reductions posed by climate change, elevated levels of CO2 have been shown to reduce important nutrients including protein, iron and zinc in a wide range of plants “to varying degrees” depending on the species, the report states. Continued increases in CO2 levels are projected to cause reductions “in a wide range of minerals and nutrients” of 5-10%, depending on the crop.

The specific impacts of climate on agriculture vary by crop and by region. In eastern Asia and northern Europe, climate change has so far increased wheat yields, the report notes, while its effects are “mostly negative” on crop yields and quality across sub-Saharan Africa, South America, the Caribbean, southern Asia and western and southern Europe.

Most research into the effects of climate change on crops has focused on staple crops, such as maize, rice and wheat, but “emerging” work is beginning to focus on the yields of other crops, the report states. 

The chart below summarises the different ways that climate change is projected to affect certain types of crops. The plus signs indicate positive impacts on productivity, the minus signs indicate negative impacts and the circles indicate mixed impacts recorded in the literature. The shading shows the confidence in attribution, with darker colours indicating a higher level of confidence.

There is medium evidence but high agreement that changes in the reproductive rates and distributions of pests, pathogens, weeds and disease vectors will increase the stress on both crops and livestock under future climate change. Since 1960, there have been “significant poleward expansions” of many key crop pests and pathogens at an average rate of 2.7km per year, although different pests respond differently to climate factors.

These are “serious concerns” that are “under-researched” due to the complexity of the interactions between multiple species, the report says. As a result, “their consequences on future crop production and food security are hard to predict”. In addition to reducing yields, pests and pathogens can increase post-harvest food losses. 

There is high confidence that climate change is already impacting livestock production through both “direct impacts” – increased mortality due to heat stress – and “indirect impacts”, such as reducing the quality of grasslands used for grazing. 

Drought, rising temperatures and other drivers are “reducing herd mobility, decreasing productivity, increasing incidence of vector borne diseases and parasites and reducing access to water and feed”, the report states. 

For each temperature increase of 1C above animals’ thermal “comfort zones”, animals consume 3-5% less food, reducing both their productivity and fertility. Higher temperatures also “enhanc[e] susceptibility…to disease” by suppressing the immune system. 

Warming of 2C by 2050 is “projected to result in 7-10% declines in livestock numbers” globally, although there are persistent uncertainties around the future productivity and composition of grazing lands, the report notes.

The report states with high confidence that the effects of climate change will also “significantly alter” the availability and quality of aquatic foods. 

Warming, ocean acidification and declining oxygen levels will all have negative impacts on key fisheries and aquaculture species, the report says, while inland and coastal aquatic systems will additionally be affected by sea level rise. (See “What impact is global warming having on marine life?”)

One study cited in the report found a 4% reduction in the “maximum sustainable yield of several marine fish populations” due to ocean warming globally between 1930 and 2010, with some regions experiencing much higher declines. 

Climate change’s impacts on fisheries “will be particularly high in tropical regions” due to large reductions in catch, the report states. These changes “can have significant consequences for human nutrition”, particularly in lower-income countries where fewer nutritional alternatives are available.

The report finds that climate change’s impacts on water availability is an “emerging issue” and notes that “increased occurrence of drought combined with limited access to irrigation water is already a key constraint” on agriculture. Drought-related crop loss has “increased in recent years”, and has affected “about 75% of the global harvested area”, the report says. 

The report also warns of the risk of “multi-breadbasket failures”, in which synchronous droughts or other extreme weather events affect crop production in multiple regions of the world. These risks “had not been quantified” when AR5 was produced.

There is limited evidence that “synchronised crop failures are increasing with ongoing climate change” and medium confidence that these risks will increase. 

“Social inequalities”, such as gender, socioeconomic status and ethnicity, “can compound vulnerability” to the effects of climate change for both producers and consumers, the report says. It notes that women are “more vulnerable” to climate-related food insecurity than men and Indigenous livestock keepers are at higher risk than their non-Indigenous counterparts due to “historical land dispossession, discrimination and colonialisation”.

The report states that climate change is already affecting “all dimensions of food security”: availability, access, utilisation (food quality and safety) and stability. As a result, there is high confidence that the number of people at risk of “hunger, malnutrition and diet-related mortality” will increase in the future. 

These projections range from 8 million more people under SSP1-6.0 to 80 million under SSP3-6.0 as “compared to a world with no climate change”. Nearly 80% of this at-risk population is projected to occur in Africa and Asia.

The report notes with high confidence that there are “various adaptation options [that] are currently feasible and effective at reducing climate impacts”. These include sustainable resource management, incorporating Indigenous and local knowledge and diversifying crops and species. However, there are many financial barriers to implementing these options and “vastly more public and private investment is required” to do so.

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6. What risks does climate change pose to the world’s cities?

Urban areas are home to more than half of the world’s population – and are constantly growing. Between 2015-20, urban populations grew by more than 397 million people – with more than 90% of growth situated in “less developed regions”, the report finds. 

The report projects that by 2050, an additional 2.5 billion people could be living in urban areas. It adds that roughly 90% of this increase is expected to be in Asia and Africa – with India, China and Nigeria alone responsible for 35% of the growth. 

Since the AR5 report, “unplanned and informal” cities – particularly in Asia and Africa – have expanded rapidly. More than half of the urban population in sub-Saharan Africa and roughly one-third of South Asia’s urban population were living in informal housing in 2018, according to the AR6 report.

It goes on to explain that cities are often hotspots for climate extremes, such as heatwaves and flooding – due to a combination of their location, population density and concentration of buildings and infrastructure. 

For example, it says that most of the population exposed to heatwaves in the coming decades will live in urban regions – in large part because the urban heat island effect can add 2C to local warming. Cities in mid-latitudes are particularly at risk from rising temperatures – and could be “subject to twice the levels of heat stress compared to their rural surroundings under all RCP scenarios by 2050”. The report adds:

“Depending on the RCP, between half (RCP2.6) to three-quarters (RCP8.5) of human population could be exposed to periods of life-threatening climatic conditions arising from coupled impacts of extreme heat and humidity by 2100.”

Unsurprisingly, exposure to heat islands is uneven – with low-income communities, children, elderly people, disabled people and ethnic minorities more exposed. For example, the report highlights research from South Africa, which shows that “housing occupied by poor communities regularly experience indoor temperature fluctuations that are between 4C and 5C warmer compared to outdoor temperatures”.

The figure below shows the distribution of the global population exposed to hyperthermia – abnormally high body temperature – from extreme heat for a) the present day; b) in 2050; and c) in 2100. Future projections are shown for a range of RCP scenarios. Red shading indicates the highest exposure, while yellow indicates the lowest exposure. The top 15 urban areas by population size are named on the map.

The report also highlights that urban expansion and changing rainfall patterns could cause nearly one third of all “major cities” worldwide to exhaust their current water resources by 2050. 

Meanwhile, it finds that flooding is a key issue for cities, which have a high density of people and infrastructure, and have large areas of “impermeable surfaces” that prevent rainfall from easily soaking into the ground. It adds this many cities are located near the sea, increasing the risk of coastal flooding:

“Much of the world’s population, economic activities and critical infrastructure are concentrated near the sea (high confidence), with nearly 11% of the global population, or 896 million people, already living on low-lying coasts directly exposed to interacting climate- and non-climate coastal hazards.”

The report has high confidence that climate change will cause sea levels to rise and increase the severity and frequency of tropical cyclone storm surges, driving higher levels of risk coastal flooding. 

By 2050, more than a billion people located in low-lying cities and settlements will be at risk from “coastal-specific climate hazards”, the report says with high confidence. However, it notes that the amount of damage caused will be dependent on future warming levels and socioeconomic scenarios.

Between $7-14tn of coastal infrastructure assets will be exposed by 2100, according to the report – affecting sectors including transportation, housing, power production and “information technology”.

For example, the report notes that even if warming is limited to 2C above pre-industrial temperatures, the number of airports at risk of storm surge flooding could rise from 269 to 338. It adds that the airports affected are disproportionately busy and currently account for up to 20% of the world’s passenger routes.

Population growth will also be a key driver of increasing flood risk – as the report is virtually certain that “economic development is disproportionately concentrated in and around coastal cities and settlements”.

One projection, for example, says that urban land will expand by 0.6-1.3m km2 between 2015-50. Even without accounting for the impacts of climate change, this means that the urban land exposed to floods and droughts will increase by more than 2.5 times between 2000 and 2030.

The figure below shows risks to people, land and infrastructure from a 1-in-100 year coastal flood event – where yellow indicates no sea level rise and purple indicates two metres of additional sea level rise, compared to 2020 levels.

The size of the circle indicates the magnitude of the impact. The top left quadrant of each circle shows the number of people affected, top right shows the number of flights disrupted, bottom left shows the kilometres of coastline affected, and bottom right indicates whether sea level rise will have a positive or negative impact on wetlands. 

There is medium evidence that coastal regions with fast-growing populations in Africa, southeast Asia and small islands will be particularly at risk of flooding over the 21st century. 

In an FAQ explaining why cities are especially vulnerable to the impacts of climate change, the report also points to a failure in governance, which allows the gap between rich and poor communities to grow:

“Demographic change, social and economic pressures and governance failures that drive inequality and marginality mean that increasing numbers of people who live in towns and cities are exposed to flooding, temperature extremes and water or food insecurity. This leads to an adaptation gap, where rich neighbourhoods can afford strategies to reduce vulnerability while poorer communities are unable to do the same.

“Although this would be so even without a changing climate, climate change increases the variability and extremes of weather, exposing more people, businesses and buildings to floods and other events. The combination of rising vulnerability and increasing exposure translates to a growth in the number of people and properties at risk from climate change in cities worldwide.”

The report also discusses the issue of air pollution in cities – noting that 95% of the global population currently live in regions where fine particulate matter (PM2.5) floating in the air exceeds the World Health Organisation guidelines.

It says that future emissions of air pollutants will broadly decline by 2050, as societies “become wealthier and more willing to invest in air pollution controls”. However, it adds:

“Whereas cities in East Asia and South Asia currently have large exposure to anthropogenic air pollution, African cities may emerge by 2050 as the most polluted because of growing populations and demand for energy, increased urbanisation, and relatively weak regulations to control emissions.”

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7. What does the IPCC report say about public health, conflict and migration?

The SPM states with very high confidence that climate change has adversely affected the physical health of people worldwide and the mental health of people in assessed regions. 

One of the more obvious impacts of climate change on human health is extreme heat – which is linked to severe dehydration, organ failure, cardiovascular disease and even death, the report says.

However, it emphasises that the impacts of heat stress are not spread equally across the world. Some regions – including parts of India, the Persian Gulf, the Gulf of California and the southern Gulf of Mexico – are especially hard hit, and are “already experiencing heat stress conditions approaching the upper limits of labour productivity and human survivability”.

Since the AR5 in 2014, greater evidence has also emerged of the detrimental impacts of climate change on mental health, the report says. Heat is “one of the best-studied aspects of climate change observed to reduce wellbeing”, according to the report. It says that increasing temperatures are linked to higher hospital admissions for mood and behavioural disorders, “experiences of anxiety, depression, and acute stress” and suicide rates.

The report emphasises that extreme weather events, such as heatwave, wildfires, floods and droughts, are already becoming more frequent and intense – driving rising mortality rates. Over 1998-2017, there were 526,000 deaths from 11,500 extreme weather events globally, it says.

Disruption to infrastructure and basic services in the aftermath of extreme weather events can also be highly damaging for the affected communities. The disruption is often associated with increased violence against women, girls and vulnerable groups – including “increased risk of domestic violence, harassment, sexual violence and trafficking”.

Research also finds that extreme weather events, such as floods, heatwaves and wildfires, can trigger post-traumatic stress disorder, anxiety, and depression. The report adds that “sub-Saharan African children and adolescents, particularly girls, are extremely vulnerable to negative direct and indirect impacts on their mental health and wellbeing”.

The climate is also a driving factor in the spread of a range of diseases, the authors say. For example, the range of mosquitoes is expanding as temperatures rise, allowing mosquito-borne diseases, such as dengue fever and malaria, to spread to new areas.

The map below shows the projected changes in potential abundances of Aedes aegypti – a mosquito that can spread dengue fever, Zika and yellow fever – over 2090-99, under a scenario of around 2C of warming by 2100 (top, RCP2.6) and a scenario of very high emissions (bottom, RCP8.5). 

The report projects that climate change will increase the risk of dengue fever in all continents. Compared to 2015, an additional 1 billion people are projected to be at risk of dengue exposure by 2080 under a mid warming scenario (described as “RCP4.5/SSP1”), and 5 billion under a high warming scenario (“RCP8.5/SSP3”), the report finds.

Warming combined with an increase in heavy rainfall and flooding is already increasing the incidence of diarrheal diseases such as cholera, the report finds. Meanwhile, the incidence of waterborne diseases is expected to increase in Africa in the coming decades due to rising temperatures and drought.

The report projects that by 2050, an extra 250,000 deaths each year from “climate-sensitive diseases and conditions” will be “attributable to climate change” (compared to the 1961-91 average, under a mid-emission scenario).

Excess deaths will be dominated by heat deaths in Asia and high income countries, childhood undernutrition and diarrheal disease in Africa and Asia and malaria in Africa, it says. Overall, more than half of the excess mortality will be seen in Africa, it adds.

The figure below shows the projected additional annual deaths from dengue, diarrheal diseases, malaria, heat and undernutrition attributable to climate change in 2030 and 2050, compared to a 1961-90 baseline.

For each region, the two bars show the additional deaths attributable to dengue fever (dark blue), diarrhoea (orange), malaria (light blue), heat (red) and undernutrition (green), in 2030 (left) and 2050 (right). The total deaths in each continent in 2030 and 2050 are shown by the black and white circles.

The report also says that Covid-19 has “aggravated climate risks”. For example, when extreme events struck, social distancing rules reduced the capacity of temporary shelters. The pandemic shows “the interconnected and compound nature of risks, vulnerabilities, and responses to emergencies”, the report says.

Meanwhile, the authors say there is high confidence that “climate hazards are a growing driver of involuntary migration and displacement and are a contributing factor to violent conflict”. Extreme weather events can drive migration in two ways, the report says – for example, directly through a cyclone destroying a house, or, for example, indirectly from long-term losses due to drought.

Most climate-related migration occurs within national boundaries, according to the report, which says that an average of 20 million people per year have been displaced internally by weather-related extremes since 2008. It adds that storms and floods rank as the most common drivers of displacement.

The figure below shows the number of people displaced every year over 2010-20 by extreme weather events, grouped by continent.

South, east and south-east Asia have seen the highest number of people displaced per year – largely to tropical cyclones and “extreme storms” – followed by sub-Saharan Africa, the report says. It also highlights that small-island states in the Caribbean and South Pacific are disproportionately affected, relative to their small population size.

The report adds that refugee and internally displaced people settlements are “disproportionately concentrated in regions that are exposed to higher-than-average warming levels and specific climate hazards, including temperature extremes and drought” – such as “the Sahel, the near east and central Asia”. 

As the planet warms, migration is likely to increase, the report finds. For example, for every 1C of extra warming, the global risk of involuntary displacement due to flooding increases by 50%.

In the latter half of this century, current emissions pathways will put hundreds of millions of people at risk of displacement due to hazards including rising sea levels, floods, tropical cyclones, droughts, extreme heat and wildfire, according to the report. However, it adds that numbers are strongly dependent on socioeconomic conditions.

For example, displacement in Latin America, sub-Saharan Africa and South Asia by 2050 could vary between 31-143 million people depending on future emissions and socioeconomic development trajectories.

In addition to geographic inequality, the report highlights the gender inequality in migration:

“Women tend to suffer disproportionately from the negative impacts of extreme climate events for reasons ranging from caregiving responsibilities to lack of control over household resources to cultural norms for attire.”

Climate change is also expected to reduce water availability. Existing literature linking water insecurity to conflict is limited, but the report says “the large majority acknowledges” that limited water availability can “exacerbate tensions”. For example, in Syria, drought has aggravated existing water and agricultural insecurity – but the report says that “whether drought caused civil unrest in Syria remains highly debated”.

The report cites analysis which suggests that 2C warming would increase the probability of “conflict risks” by 13%, due to reduced food and water security, and disruption to lives and livelihoods. This instability can lead to “civil unrest” in some regions, which is often linked to an increase in violence against women, girls and vulnerable groups, the report warns.

The report concludes that “climate-related migration outcomes are diverse”, adding that future migration and displacement patterns will depend on “not only on the physical impacts of climate change, but also on future policies and planning at all scales of governance”.

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8. How does climate change affect poverty and progress towards the sustainable development goals?

The eighth chapter of the report deals with the societal consequences of climate change and “irreversible consequences” for the most vulnerable. 

It assesses impacts through the lens of poverty, livelihoods and vulnerability of  people, aiming to understand “why climate events trigger sudden and slow-onset disasters, and how the most severe, acute and chronic impacts cause and deepen human suffering”. 

Vulnerability is defined by the report as “the propensity or predisposition to be adversely affected and encompasses a variety of concepts and elements, including sensitivity or susceptibility to harm and lack of capacity to cope and adapt” to climate-related hazards. 

The authors note with high confidence that historical inequalities play a key role:

“Vulnerability is a result of many interlinked issues concerning poverty, migration, inequality, access to basic services, education, institutions and governance capacities often made more complex by past developments, such as histories of colonialism.”

The report says that the world’s poor and their livelihoods are particularly vulnerable to climate change as they have fewer assets, limited access to funding, technology and political influence. These challenges mean they have fewer resources to adapt. 

Climate change impacts tend to worsen inequality, it states, given that they disproportionately affect people who are disadvantaged and, therefore, “reduces their ability to cope and recover”. 

One of the key factors that drive disproportionate impacts on the poor is lost agricultural income, the report says with high confidence, the second being the impact of hazards on health, “a primary resource that the poor rely on”. 

The figure below shows the impacts of 23 climate hazards on nine key livelihood resources on which the world’s poor rely most. Each category of impacts is assigned a confidence statement, based on the weight of evidence assessed in the report: high (red shading), medium (orange) and low (green) confidence.  

Additionally, groups that face “[d]isadvantage due to discrimination, gender and income inequalities and lack of access to resources” could have fewer resources to prepare, react, cope and recover from adverse climate change impacts “and are therefore more vulnerable”. This vulnerability can then increase due to climate change impacts in “a vicious cycle”, as shown in the diagram below.

The report highlights new evidence that shows that the risk of “extreme impoverishment” increases for low-income communities experiencing back-to-back climatic events, without time to recover. A “key risk for the poor” is “shocks to specific livelihood assets”, such as land and housing, with the urban and rural landless poor struggling to rebuild them after disasters. 

Evidence also exists that climate change impacts drive recurrent poverty and force the poor into persistent extreme poverty traps. This is especially true when wages remain stagnant, costs of living, such as food and healthcare, rise, mobility is restricted and when people face ethnic or social discrimination or conflict. 

Even under medium warming scenarios, there is high agreement and enough evidence to suggest that climate risks to poverty “would become severe if vulnerability is high and adaptation is low.”

The chapter assesses the latest literature on how multi-dimensional poverty and human vulnerability are measured and it examines how different indexes rank “global vulnerability hotspots”. 

The report states with high confidence that average mortality from floods, drought and storms over the past decade was 15-times higher for “very highly vulnerable” regions and countries – including Mozambique, Somalia, Nigeria, Afghanistan and Haiti – versus regions and countries ranked “very low” on the scale of vulnerability, such as the UK, Australia, Canada and Sweden. According to studies the report assessed, 11-times more people are adversely affected by a hazard event in “very highly vulnerable” regions and countries, compared to countries with very low vulnerability.

A third of all the evidence the IPCC assessed on livelihood impacts came from just three countries – India, Nepal and Bangladesh, “indicating accumulating experience with livelihood impacts in South Asia”. While evidence of impacts was more limited in literature assessed from Central Asia and the Caribbean, its weight “is still robust”, the authors note. Of all industrialised nations, “there is highest confidence that climate change has impacted livelihood resources in the US”.

According to additional assessments, approximately 3.6 billion people live in low and lower middle-income countries, “which are most vulnerable and disproportionally [sic] bear the human costs of disasters due to extreme weather events and hazards”.

The report states with high confidence that the most vulnerable regions in the world include east, central and west Africa, south Asia, Micronesia and Melanesia and Central America. It estimates that 1.6 to 3.3 billion people are living in countries classified as very highly or highly vulnerable, while 0.8 to 2 billion people reside in regions classified as least vulnerable. The authors add:

“Recent studies suggest that the total population of all countries classified as most highly vulnerable is projected to grow significantly.”

Of all climate hazards, warming trends and drought “pose greatest risks to the widest array of livelihood resources” the report says, given that they are “particularly detrimental” to human and crop health and, therefore, to long-term livelihood security and well-being. 

Unlike other hazards that impact largely “private livelihood resources”, such as houses and incomes, the authors note with high confidence that droughts and warming “also affect common pool resources, such as rangeland, fisheries and forests”. Multiple hazards “undermine” these ecosystems that Indigenous Peoples rely on for food security and “have sustainably managed over the long-term”. 

One of the studies it assessed found that across 92 developing countries, the poorest 40% of the population experienced losses from climate hazards that were 70% greater than the losses of people with average wealth. 

By 2030, it estimates that the number of people living in extreme poverty is set to increase by 122 million. 

If warming continues “under high emissions scenarios”, losses and damages will likely be concentrated among the poorest vulnerable populations, the authors say. This is likely to “force economic transitions” among the poorest groups, moving away from agriculture even more rapidly towards cities and other forms of labour.

The authors note with medium confidence that climate change and vulnerability together “threaten the achievement of the UN Sustainable Development Goals (SDGs)”, especially  progress towards goals such as no poverty (SDG1), zero hunger (SDG2), gender equality (SDG5) and reducing inequality (SDG10). 

For example, the report reviews a 2021 study from India that shows increased risk of intimate partner violence after climate disasters. The study’s authors note that “societies vulnerable to climate change may need to prepare for the social disasters that can accompany disasters revealed by natural hazards”. 

The report lists several examples to draw attention to these intersecting impacts of poverty, inequality and vulnerability, with lessons for designing adaptation strategies for current and future climate change.

In Box 8.5, the report cites the case of the 2018 drought in South Africa’s western Cape region where a combination of “poor communication” in the early stages of the drought and “lack of trust” in the administration lead to “near-panic” at the threat of “Day Zero” in Cape Town when water would run out. 

The report observes that while “ordinary communities” displayed “unprecedented degrees of resilience – including behavioural and attitudinal shifts and technological innovation across the full socio-economic spectrum” – “‘gated adaptation’ by elites” only served to further inequality in access to water. 

The case study highlights that African cities must plan for slow-onset shocks and integrate equity and sustainability into disaster planning, while ensuring water tariff models are flexible enough to “prioritise…the urban poor” and do not “deepen existing inequalities”.

The report also uses Box 8.8 to examine the impacts of 2009’s Cyclone Aila on different income groups in Bangladesh and the coping mechanisms and adaptation actions that people adopted.

Migration, infrastructural changes or pursuing alternative livelihoods due to irreparable loss and damage indicate that community or household actions can only address “typical challenges”, such as seasonal shifts in rainfall, the authors say. However, they are less effective in addressing extreme events that have long-lasting impacts, indicating limits to “autonomous” – spontaneous, unplanned – adaptation by affected communities.

The principle of “common but differentiated responsibilities and respective capabilities” (CBDR-RC) is closely linked to climate justice and acknowledging countries’ different development situations. 

The report reviews literature published in the post-Paris Agreement regime for how effectively and adequately it captures CBDR-RC in adaptation provisions. It analyses not just Article 7 of the agreement, where adaptation is found, but also the financial provisions to “operationalise” CBDR-RC.

It points to divergence in literature around questions of whether the most vulnerable nations are prioritised, whether “adaptation is placed on an equal footing as mitigation” or whether little has moved since Paris if the world needs a quantitative goal for adaptation needs. 

The authors note elsewhere in the report that “there has been a continued heavy imbalance” in favour of mitigation finance, with adaptation receiving only 5% of tracked climate finance, “around $30bn (compared to $532bn for mitigation)”. 

It observes that multilateral and bilateral donors often fail to prioritise highly vulnerable countries for adaptation projects and that foreign funding “may not map onto more recently developed administrative traditions”, leading to the “dominance” of donor-led governance models. 

A 2017 study the report cites estimates that less than 10% of climate finance committed from international, regional and national climate funds went to locally focused projects in  developing countries between 2003 and 2016. It suggests “a need to rethink” how most affected groups are to build sufficient climate resilience, given fiduciary and governance challenges.

The report lists Burkina Faso, Mali and Zambia as developing countries that are not only among the “most vulnerable to climate change”, but “least able to mobilise the finance needed to adapt to its impacts”. Mali, it notes elsewhere, still reels from the effects of a drought in 1982-84, showing that climate change can have persistent impacts on livelihoods and food security long after an extreme event has passed.

The authors say with high confidence that “the poorest groups in society often lose out” in accessing any climate aid, with women and girls disproportionately impacted.

They also note that least developed countries (LDCs) and small-island developing states (SIDs) currently receive only 14% and 2%, respectively, of total climate finance. They observe that vulnerable, developing countries shoulder additional debt burden linked to their exposure to climate risks. This is “further exacerbated by the recession and debt distress accompanying the Covid-19 pandemic”.

Debt relief by public creditors, green recovery bonds, debt-for-climate swaps or SDG-aligned debt instruments could help vulnerable countries address their debt burden, the authors say, “freeing up” investment for adaptation and “a green economic recovery”. 

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9. How is the world adapting to climate change?

Climate adaptation is far more prominent in the new report than any previous IPCC assessments, reflecting both an expansion of knowledge and heightened urgency.

It states that the goals of climate change adaptation are to “reduce risk and vulnerability to climate change, strengthen resilience, enhance wellbeing and the capacity to anticipate, and respond successfully to change”. 

Diverse examples of this in action span the report, including:

• Chapter 2: Planting trees “in the right place” to provide shade for people, livestock, crops and even water sources, which can help to keep temperatures low and maintain fisheries.
• Chapter 3: Restoration of mangroves, saltmarshes and seagrass meadows, which can both remove CO2 from the atmosphere and protect coasts from the impacts of storms and sea-level rise.
• Chapter 4: Farmers in semi-arid areas adapting to changing rain patterns by using irrigation.
• Chapter 5: Taking an agroecological approach to reduce risk in food systems, improve food security and reduce costs.
• Chapter 6: Managing flood risk in cities by installing flood proofing in properties, improving drainage along roads, incorporating nature-based solutions, constructing flood defences and reducing runoff from land upstream.
• Chapter 7: Supporting “safe and orderly movements of people”, protecting migrant rights and facilitating financial flows “between sending and receiving communities”, to adapt to climate migration.
• Chapter 8: Public and private investment in different types of assets, including water and sanitation, education and healthcare, to help make the world’s poorest people more resilient to climate change.

In the 1990s, studies of adaptation were relatively limited, the report says – there was an assumption that curbing greenhouse gases would be effective and timely, meaning there would be little need for societies to adapt.

The WG2 report of the IPCC’s fourth assessment (AR4) – published in 2007 – included one chapter about adaptation, while the AR5 WG2 report expanded this to four. In contrast, AR6 states that its authors have integrated adaptation “comprehensively throughout the report”.

This change has come about as the impacts of climate change have become more apparent and adaptation projects have got up and running, the authors note.

Nevertheless, the report still emphasises that, overall, “the extent of adaptation-related responses globally has been low”. The most common actions are changes to people’s behaviour in Africa and Asia in response to drought, flooding and rainfall, as well as local governments protecting infrastructure and services, such as water supplies.

The report also concludes with high confidence that, barring some measures to deal with flooding and extreme heat, there is “negligible evidence that existing responses are adequate to reduce climate risk”. Furthermore, “major knowledge gaps persist in modelling and analysis” of climate adaptation.

These are all important issues because, as the report notes, even with emission reductions sufficient to meet the Paris Agreement goals, “transformational adaptation will be necessary”. 

There are numerous targets in place for adaptation, including the Sendai Framework for Disaster Risk Reduction and the finance-oriented Addis Ababa Action Agenda. The report also notes that the UN’s overarching Sustainable Development Goals would be difficult to reach without successful adaptation to climate change.

The Paris Agreement itself also includes a “global goal on adaptation”, albeit one that has been described as “unacceptably vague”. A key issue identified in the new AR6 report is that specifying adaptation goals is harder than for mitigation, which can simply be judged by volumes of emissions.

Not only do adaptation actions “span a vast range of activities”, their success depends “more strongly on context”, the report says:

“A different, often more diffuse set of actors are involved, and it is often hard to distinguish what activities count as adaptation.”

With all of these challenges in mind, the report identifies three metrics by which to assess adaptation: effectiveness, feasibility and justice.

Effectiveness is broadly defined as the extent to which a solution reduces climate risk, although it can also include economic benefits and measures of wider societal wellbeing.

Feasibility is the extent to which it is considered possible and desirable, “taking into consideration barriers, enablers, synergies, and trade-offs”.

While previous IPCC reports did not explicitly discuss climate justice in their adaptation chapters, this one explicitly shows “how better outcomes are obtained by choosing just ones”. It states with high confidence that adaptation goals at the international, national and local levels require “engaging with the concepts of equity, justice and effectiveness”.

Climate justice can mean many things to many people, but the report notes that generally “it is common to distinguish between distributive justice, procedural justice and recognition”. These are defined as follows:

• Distributive justice: Adaptation solutions aim to achieve fairness between individuals, states and generations.
• Procedural justice: Such actions should also involve “genuine, not merely formal” participation from people affected, requiring communities to be well-acquainted with climate risks and given a voice in adaptation planning.
• Recognition: This involves “basic respect and robust engagement with and fair consideration of diverse values, cultures, perspectives, and worldviews”. It is closely tied with the first two and without it actors “may not benefit” from them.

The report states that two key concepts – “adaptation gaps” and “limits to adaptation” – frame its assessment of existing adaptation efforts:

“Within the limits, adaptation gaps can be closed by increased and more successful adaptation actions. Beyond the limits, only mitigation can close adaptation gaps.”

Understanding of the size of the current adaptation gaps remains limited, but the report states with high confidence that “significant adaptation gaps exist”, citing a lack of sufficient adaptation finance as one driver of this.

The report acknowledges that research into adaptation generally has seen a major increase over the past few years.

One study cited shows an annual average increase of 28.5% in climate change adaptation publications between 1978 and 2020, with the greatest increase in publications occurring over 2006-10 – up 540% from the previous five years.

Adaptation research during the 1990s and 2000s was “primarily academic”, but in recent years as adaptation projects have got underway around the world, the report says it “now includes a proliferation of on-the-ground experience”.

Investigation of the topic has also spread from looking at “engineered and technical options” to social, institutional and governance dimensions as well, it adds.

The figure below is based on a review of 1,682 scientific publications over 2013-19 reporting on adaptation-related responses. The darker the colour, the more publications have been undertaken for that sector and climate hazard.

Nations have been encouraged to monitor and evaluate their adaptation plans, partly through the Paris Agreement’s global stocktake, which will take place every five years starting in 2023.

However, the report finds that despite advances in wider understanding of adaptation, overall monitoring and evaluation of adaptation projects remain a blind spot.

It highlights that such long-term activities are “much less common than adaptation assessment prior to implementation”. This is an issue as long-term evaluation allows for an understanding of what works and what does not. 

The report states with medium confidence that one-third of nations have “undertaken steps” to monitor and evaluate adaptation efforts, “fewer than half of these are reporting on implementation”. 

One review, cited in the report, found that only 2.3% of nearly 1,700 articles identified by the Global Adaptation Mapping Initiative provided evidence of risk reduction following implementation of adaptation projects.

Beyond peer-reviewed scientific papers and other evidence that has traditionally fed into the IPCC process, the new report also emphasises the importance of Indigenous and local knowledge. It concludes with high confidence that such approaches “can help diversify knowledge that may enrich adaptation policy and practice”:

“Indigenous peoples have been faced with adaptation challenges for centuries and have developed strategies for resilience in changing environments that can enrich and strengthen current and future adaptation efforts.”

The report also considers what governments and other relevant organisations need to do to make adaptation happen.  

It finds that adaptation efforts “require strong, usually multi-level governance systems”, spanning multiple levels of jurisdiction and decision-making, including at global, regional, national and local levels.

The report also states that “mainstreaming” adaptation into existing governance can support transformative adaptation and expand the “solution space” – defined as “the space within which opportunities and constraints determine why, how, when and who adapts to climate risks”. One example is urban planners considering adaptation in their city plans from the outset.

Finance is also a key issue identified in the report, highlighted as a “crucial enabling condition and shaper of the solution space”. It notes that the potential return on investment is large, suggesting that a $1.8tn investment in measures including early warning systems, global mangrove protection and climate-resilient infrastructure would yield $7.1tn in benefits.

However, the report also repeats a common refrain, which came to a head at the recent COP26 summit in Glasgow, that “the current public and private financial flows to adaptation are much smaller than needed”. It states with high confidence that just 4-8% of climate finance has gone to adaptation efforts in recent years.

According to Climate Home News, adaptation finance proved to be one of the more contentious topics during negotiations over the SPM. While the US reportedly objected to the emphasis on adaptation finance, the final document includes several references to it, including the “essential” need for “enhanced mobilisation” and access.

The Earth Negotiations Bulletin reported that the US, Australia, France and Ireland resisted a request by India to include specific numbers illustrating the shortfall in adaptation finance in the final SPM.

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10. Are there limits to what adaptation can achieve?

The report includes lengthy discussions on the limits to adaptation – the points at which it is difficult or even impossible to accommodate the changes the world is undergoing.

This idea of an adaptation limit, first introduced in AR5 in 2014, is defined as “the point at which an actor’s objectives or system’s needs cannot be secured from intolerable risks through adaptive actions”.

Such a concept “strongly affects any appropriate balance among adaptation and mitigation actions” as a failure to cut enough emissions could render adaptation futile, the report says. In other words, if there are numerous limits on adaptation, mitigation efforts will need to be ramped up.

These limits are categorised as either “soft” or “hard’, and are distinguished by the extent to which it is possible to overcome them.

Soft limits tend to be those set by people. Flood defences might not be built because there is not enough money made available, a lack of stable governance or too few people with the skills to construct them, for example.

Hard limits, on the other hand, are largely associated with natural systems. Sea level rise and storms may reach a point where flood defences are no longer sufficient to protect people.

Chapter 2 of the report – which addresses terrestrial and freshwater ecosystems – gives a sense of the magnitude of some of these unadaptable limits, stating:

“In general, adaptation measures can substantially reduce the adverse impacts of 1-2C of global temperature rise, but beyond this losses will increase, including species extinctions and changes, such as major biome shifts which cannot be reversed on human timescales.”

IPCC special reports have delved into these areas, with the ocean and cryosphere report identifying upper limits for ecosystems and communities around coral reefs, urban atoll islands and low-lying Arctic locations, and the land report doing the same for coastal regions and areas affected by thawing permafrost.

Nature-based solutions – such as coral reefs, mangroves and marshes, all of which can help adaptation efforts – will likely reach hard limits of their own as the planet warms beyond 1.5C, the report says.

The report states that understanding where these limits lie gives a sense of the urgency required, noting with high confidence that:

“Adaptation is urgent to the extent that soft adaptation limits are currently being approached or exceeded and that achieving levels of adaptation adequate to address these soft limits requires action at a speed and scale faster than that represented by current trends.”

The report also includes discussions of “residual risk”, a term defined as “the risk that remains after actions have been taken to reduce hazards, exposure and/or vulnerability”. For the most part, this is what remains after the upper limits of adaptation have been reached.

As with climate adaptation more broadly, evidence is somewhat lacking when it comes to adaptation limits. The report says there is high agreement but only medium evidence that there are limits to adaptation across regions and sectors. 

The figure below gives a sense of the available evidence on where these limits occur, with darker colours indicating more evidence across a sample of 1,682 studies. It shows that the most detailed picture of future limits on adaptation exists for Latin America and small islands.

The report examines the evidence for limits on adaptation that already exists, in one section zooming in on the examples of agriculture across Asia, livelihoods in Africa and general impacts on small-island states.

Examples of soft limits to adaptation include difficulty preparing for coastal floods in Samoa due to financial, physical and technological constraints, and small-scale farmers in Bangladesh struggling to adapt to riverbank erosion while wealthier farmers have the money to implement responses.

Hard limits include springs running dry in Nepalese farming communities and land scarcity in parts of Africa when organic cotton production is introduced to support more sustainable livelihoods.

The residual risks identified are stark, including “collapse of economies and livelihoods and reduced habitability of islands” and poorer households in Africa “becoming trapped in cycles of poverty”, the report says.

With many parts of the world facing such bleak prospects, the IPCC report has a new focus – a key development since AR5 – on “transformational adaptation”. 

Most adaptation is “incremental”, meaning it only modifies existing systems. Transformational adaptation, on the other hand, “changes the fundamental attributes of a social-ecological system”. This relates to the discussion of limits because, as the report explains:

“Transformational adaptation can allow a system to extend beyond its soft limits and prevent soft limits from becoming hard limits.”

One example given is that building a seawall to protect a community is incremental adaptation, while changing land-use regulations in that community and establishing a programme of managed retreat could be transformational adaptation.

The map below shows that, based on the available literature, there is currently little evidence for this kind of adaptation taking place around the world (light colours indicate low evidence for such action).

The report notes that while such changes may be necessary to overcome limits to adaptation, the approach is “not without risks”. This is because changes that impact every level of society can “disturb existing power relationships” within that society, and they can “unfold in difficult to predict and unintended ways”.

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11. What does the report say about ‘loss and damage’?

“Loss and damage” is highlighted in the report as an area of increasing importance in both international climate policy and climate science. 

Broadly, this concept refers to harms caused by climate change, including both rapid-onset events, such as hurricanes, and slow-onset events, such as gradual sea level rise.  

The topic was a rallying point at the recent COP26 summit in Glasgow as vulnerable nations unsuccessfully pushed for a new funding facility to address such impacts. It is expected to remain a highly contested issue in future climate negotiations.

Initially pushed by small-island developing states to describe the impacts of rising sea levels – and, thus, seek compensation – the concept has expanded in scope over the years. 

Different actors have defined loss and damage in different ways, using it to describe both climate change impacts and responses to those impacts. The report identifies a handful of these “perspectives”:

• Adaptation and mitigation: Stresses the need to avoid dangerous warming as all human-induced climate impacts are linked to loss and damage. 
• Risk management: Emphasises the connections between disaster risk reduction, climate change adaptation and humanitarian efforts.
• Limits to adaptation: Focuses on “residual loss and damage”, meaning the impacts that remain beyond the limits of adaptation and mitigation.
• Existential: Highlights the inevitable harm and unavoidable transformation for some people and systems, resulting from climate change.

The IPCC’s first assessment of the scientific literature on loss and damage came in its 1.5C report in 2018, following an intervention by concerned member countries. It identified a rise in “residual risks” as temperatures increased, such as the decline of coral reefs and coastal livelihoods.

The 2018 report concluded there was “not one definition” of loss and damage and the new WG2 report concludes that this “ambiguity has persisted and a policy space for [loss and damage] has not clearly been delimited”. This vagueness and lack of a “concrete remit” makes policy formulation “complex”, it notes.

Nevertheless, the report describes a “coalescence in dialogue” among scientists, civil society and policy makers that includes “risk management, limits to adaptation, existential risk, finance and support including liability, compensation and litigation”.

It notes that researchers have begun compiling loss and damage inventories, including some of the more intangible aspects such as cultural loss. Despite this, it says systematic risk assessments of loss and damage and adaptation limits “remain scarce”.

The report also notes that there is less discussion of the “existential dimension” of loss and damage, although this is often inferred when scientists discuss issues such as the migration and relocation of communities.

While there has been some discussion of early-warning systems and other measures that would actually reduce risk, the report states that “dialogue has strongly focused on risk finance” to pay for the impact of residual risks, particularly through insurance schemes. 

It notes that researchers have explored both potential sources and mechanisms for leveraging new finance to pay for loss and damage. 

One study found that half of the academic and grey literature surveyed mentioned compensation, even though the idea of rich nations owing a climate debt to vulnerable nations is highly contentious. Others warn that litigation risks for governments and businesses may increase “as the science, particularly on attribution matures further”.

Overall, the report concludes:

“Any estimate of [loss and damage] finance needs and spending, however, remains highly speculative, as long as its exact remit including in relation to adaptation has not been clarified politically.”

The report also emphasises that assessment of non-economic losses and damages – including loss of societal beliefs and values, cultural heritage and biodiversity – is “lacking and needs more attention”. 

Examples cited in the report include large-scale loss of life and its mental health and behavioural impacts; the loss of cultural heritage sites and “sense of place” after flooding; current and future “loss of identity” for communities in glacial and island regions; and the impact of wildfire smoke on vulnerable social groups in Amazonia.

The authors say that aggregate losses and damages would be higher if such values were considered.

The complexity of defining loss and damage extends to the term “loss and damage” itself. 

As the glossary explains, the WG2 report uses capitalised “Loss and Damage (L&D)” to refer to political negotiations under the United Nations Framework Convention on Climate Change (UNFCCC), and notes that lower-case references to “losses and damages” are used in scientific literature to refer to residual effects from observed impacts and projected risks.

According to BBC News, IPCC scientists had hoped to use the term “losses and damages” as it had a “different, less political meaning” to “loss and damage”. 

Despite this, the news website reported that officials from “several richer governments” at the approval session for the report objected to any inclusion of the concept, due to concerns that it would raise the status of the issue in climate negotiations. Wealthy nations have long resisted efforts to set aside specific funding for loss and damage or accept liability for it based on their historical emissions.

According to the Earth Negotiations Bulletin, which reports from inside the negotiations, Norway and the US rejected a proposal by a group of global south nations to refer to “economic losses and damages from climate change” instead of “economic damages from climate change”.

In the end, while WG2 in its entirety still includes many references to “loss and damage”, in some parts the term was replaced with “losses and damages”.

This is interesting for anyone following the drama around “loss and damage” in the new #IPCC report.

These amendments (all from the “small islands” chapter) show language being shifted slightly to the less politically loaded “losses and damages”.

(h/t @AyeshaTandon ) pic.twitter.com/jdZYlIXv5G

— Josh Gabbatiss (@Josh_Gabbatiss) February 28, 2022

The SPM – the most politically relevant section of the report – includes no references to “loss and damage”, but does include 15 references to “losses and damages”. It states with high confidence that:

“With increasing global warming, losses and damages will increase and additional human and natural systems will reach adaptation limits.”

During the negotiations, the US had pushed for “losses and damages” to be replaced with the word “impacts” in the SPM, reported Climate Home News. 

Ultimately, while this attempted change appears to have been unsuccessful, it resulted in a reference to “widespread losses and damages to nature and people” being replaced with “widespread adverse impacts and related losses and damages”.

There have been reports of rich nations trying to water down #lossanddamage language in #IPCC SPM

But l&d still appears throughout the report, and much more than the less politicised “losses and damages”

Unsurprisingly, the terms appear a lot in chapters on poverty and islands pic.twitter.com/QsQ6isuDvl

— Josh Gabbatiss (@Josh_Gabbatiss) February 28, 2022

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12. What are the risks of ‘maladaptation’ and the unintended consequences of mitigation?

The report also explores “maladaptation”, which it describes as adaptation measures that “lead to an increase in the climate vulnerability of a system, sector or group”, either now or in the future.

“Maladaptation differs from ‘failed’ or ‘unsuccessful’ adaptation, which ‘describes a failed adaptation initiative not producing any significant detrimental effect’,” the report says.

The report says there are no “good” and “bad” adaptation choices and that the difference between adaptation and maladaptation should be viewed as a “continuum” shaped by local context.

Metrics that should be considered when assessing the success of adaptation projects include benefits to people and wildlife, potential to reduce emissions and “equity outcomes” for marginalised ethnic groups, women and low-income populations.

The report offers some examples of maladaptation. It cites a study examining the consequences of a large-scale irrigation project in Navarre, Spain, promoted by the Spanish government in response to changing climate conditions. The report says:

“Many small-scale producers could not afford the irrigation investment and had to sell or rent their land to those who joined the irrigation project. The project increased inequity, land concentration and lowered crop diversity, with small-scale producers more vulnerable to climate change.”

The report also cites colonial and post-colonial agricultural policies in India as an example of maladaptation.

“Although such policies increased national food production, they failed to address high levels of malnutrition, worsening regional inequalities, degraded natural resources and an agrarian debt crisis,” the report says.

As well as examining the potential for maladaptation, the report also explores “maladaptive mitigation”, the unintended consequences of measures to tackle greenhouse gas emissions.

It gives examples of how measures to tackle climate change may pose a risk to people or biodiversity. For example, the expansion of renewable energies such as solar and wind could impose on areas of biodiversity.

(Relatedly, a new study – covered in a Carbon Brief guest post earlier this month – says that conflicts between renewables and biodiversity protection do occur, but overlap need not be severe if renewables are deployed with appropriate policy and regulatory controls.)

The report says “the most serious emerging conflicts are between land-based approaches to mitigation and the protection of biodiversity”.

It lists two land-based approaches that could pose a serious risk: tree-planting and a technique for removing emissions from the atmosphere known as bioenergy with carbon capture and storage (BECCS).

Put simply, BECCS involves growing crops, burning them in a power plant to generate energy and then capturing the resulting CO2 before it is released into the air. The captured CO2 is then sent to an underground or undersea storage site.

Most scenarios envisaging how the world could limit warming 1.5C incorporate BECCS to some degree.

However, deploying BECCS on a worldwide scale would require vast areas of land to be converted to bioenergy plantations. This could raise large threats for the world’s biodiversity, which has already been significantly impacted by land-use change.

One study cited by the IPCC found that rolling out BECCS on a scale large enough to keep temperatures at 2C could pose such a large risk to land species that any benefit from reducing warming would be cancelled out.

A second study found that using BECCS to keep temperatures at 2C would have a greater impact on European bird species than a global temperature increase of 4C.

“To avoid the worst impacts of BECCS, it will need to be carefully targeted, according to context and local conditions and other mitigation strategies prioritised so its use can be minimised,” the report says.

On tree-planting, the report notes that replenishing formerly forested areas “can bring multiple benefits”, but planting trees in places where they do not grow naturally “can have serious environmental impacts, including potentially exacerbating the effects of climate change”.

Savannahs – grassy plains found in the tropics – are among ecosystems “that are at risk from afforestation [tree-planting] programmes”, the report says.

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13. What role can nature-based solutions play in adaptation and mitigation?

Many sections of the report deal with the effectiveness of “nature-based solutions” in climate change adaptation and mitigation.

In its current definition, the report accepts with high confidence that nature-based solutions (NbS) “provide adaptation and mitigation benefits for climate change as well as contributing to other sustainable development goals”. 

The authors note that while NbS is “not a universally accepted term…it is increasingly used in the scientific literature”. They recognise that its definition excludes actions that use nature to “solve human problems but do not provide benefits for biodiversity”. The SPM adds that the term is “the subject of ongoing debate, with concerns that it may lead to the misunderstanding that NbS on its own can provide a global solution to climate change”. 

The authors state that “ecosystem based adaptation” (EbA) – which aims to increase resilience and reduce vulnerability of ecosystems to help people adapt – could be a subset of NbS, while observing that both NbS and EbA are “themselves vulnerable to climate change impacts”.

The authors agree there is robust evidence that these solutions for people and climate can also benefit wild species and habitats, and often contribute to other SDGs.

However, “poorly conceived and designed” nature-based mitigation projects have the potential for multiple negative impacts, says the report with high confidence. They could create or exacerbate competition for land and water resources, “reduc[e] human well-being” or fail to provide mitigation that is sustainable in the long-term”.

For NbS to succeed, the report says with high confidence that it is “critical” that they support local livelihoods. “[I]ndigenous, local communities and millions of private landowners” should benefit, and be actively engaged in decision-making around NbS.

The study authors observe with high confidence that “nature-based solutions cannot be regarded as an alternative to, or a reason to delay, deep cuts in greenhouse gas emissions”. 

A separate cross-chapter box in Chapter 2 examines the definitions and effectiveness of NbS, from forests and peatlands to blue carbon and urban NbS. 

Forests

Keeping “existing natural forests” standing and sustainably managing “semi-natural forests” “is a highly effective NbS”, the report says with high confidence.

Protecting natural forests currently contributes between 5-7bn tonnes of CO2 per year (GtCO2/year) to climate mitigation efforts, it estimates. 

The assessment states with high confidence that reforestation “can be one of the most practical and cost-effective ways of sequestering and storing carbon”, while also protecting and helping biodiversity recover – particularly if carried out with “climate-resilient native or geographically near species”. It can also help improve water supply and quality in ecosystems and reduce the risk of floods and soil erosion. 

Wildfires, droughts and pest outbreaks count as severe disturbances that can cause tree mortality, pushing stored forest carbon back into the atmosphere, the report notes. These disturbances are on the rise because of climate change, prompting a “need to adapt”.

Ecological restoration with diverse species “rather than monoculture plantations” can help reduce these risks.

The report notes with very high confidence that mono-culture plantations that fail to plan for their host landscapes, do not “meaningful[ly] engage” with Indigenous and local communities, or seek their “free prior and informed consent” can “present risks to biodiversity, rights, livelihoods and wellbeing, as well as being less climate-resilient than natural forests”. 

In addition, the report warns with high confidence that afforesting savannahs, natural peatlands and other areas that do not naturally house forests “damages biodiversity and increase[s] vulnerability to climate change…so is not a Nature-based Solution and can exacerbate greenhouse gas emissions”. 

It says that remote-sensing studies can often overestimate land available for tree-planting potential, as they can fail to distinguish “between degraded forest and naturally open areas”.

Peatlands

Peatlands are “naturally high-carbon ecosystems, which have built up over millennia”, the report says. Draining, cutting and burning peat lead to the release of CO2, the authors say with very high confidence. 

Rewetting dried peatlands and preventing further cutting and burning can help restore some temperate peatlands, but “this is a process that could take many years”. 

Protecting intact “peat forests” – tropical moist forests in swampy soil – “is by far the more effective pathway both in terms of cost, CO2 mitigation and protection of food sources”, the report notes. 

In some cases, naturally treeless northern hemisphere peatlands have been drained to enable trees to be planted. This “leads to CO2 emissions”, the authors say with high confidence, and restoration “requires removal of trees as well as re-blocking drainage”.

Agroecology and agroforestry

The report considers the strategies of agroforestry and agroecology. Agroforestry refers to the integration of trees and shrubs with crops and livestock in agricultural systems. Agroecology, as the report defines, is a set of practices including “intercropping, livestock grazing mobility, organic agriculture, integration of livestock, fish and cropping, cover crops and agroforestry”.

Studies assessed in the report demonstrate that agroforestry can store 20-33% more soil carbon than conventional agriculture while also reducing fire risk.

The mitigation potential of “agroecologically-improved cropland and grazing land management” is “significant” and estimated at 2.8-4.1GtCO2e per year. 

Minimising nitrogen-based fertilisers and other synthetic inputs reduces emissions, while cover crops can increase soil carbon and reduce nitrous oxide emissions, the report says. Biodiverse agroforestry systems benefit nature and people more than simple agroforestry and conventional agriculture, it adds. 

While yields in agroforestry and organic farming are sometimes lower than intensive agriculture, the report states with medium confidence that agroforestry “can boost productivity and profit” over varying timeframes, based on the socioeconomic, political and ecosystem context.

The authors agree with high confidence that adopting agroecology principles and practices would be “highly beneficial” to maintain “healthy, productive food systems under climate change”. 

Blue carbon and oceans

“Blue carbon strategies” – which rely on ecosystems such as mangroves, marshes and seagrass meadows for their mitigation potential – are still “relatively new, with many of them experimental and small scale”, the report notes. 

While there is evidence to show that blue carbon systems often have high local rates of carbon accumulation and storage, their overall mitigation value as NbS is hard to estimate due to the “variable production” of other greenhouse gases. For example, restoring water flow in mangroves and marshes could potentially reduce methane and nitrous oxide emissions, but evidence is limited.

The report concludes with medium confidence that blue carbon strategies “can be effective NbS” for climate mitigation, but their overall global or regional potential “may be limited”. However, there is high confidence that these systems can “counteract sea level rise effects, buffer storm surges and flooding erosions”, providing climate adaptation, biodiversity, cultural and socio-economic benefits.

Restoring dunes and coastal wetlands to reduce coastal risks and act as a buffer between infrastructure and the sea yields immediate benefits, the report says, but these solutions “are not feasible everywhere”, especially in urbanised areas. 

There are limits to adaptation to accelerating sea level rise – including in geographies such as the Mediterranean – the authors note in Cross-Chapter Paper 4. This, in turn, has stimulated ideas of large-scale “geoengineering projects” such as surface height control dams at Gibraltar, which “come with unknown risks for humans and ecosystems”. Engineering-based coastal adaptation “could result in large residual impacts to coastal ecosystems”, the report notes with high confidence. 

In Chapter 3, the authors state with high confidence that, when well-designed and implemented, NbS for ocean and coastal adaptation can be “cost-effective” and “achieve multiple benefits” and “can contribute to the conservation of biodiversity in the near to mid-term”. However, their effectiveness declines with warming and must be accompanied by “urgent mitigation”.  

For instance, the report says “conservation and restoration alone will be insufficient” to protect coral reefs beyond 2030 and mangroves beyond the 2040s.

While marine protected areas do not prevent marine heatwaves, they can increase

climate resilience “by removing additional stressors” and “providing “marine plants and animals with a better chance to adapt to a changing climate”, it says. 

The report considers sustainable fishing to be an NbS, because sustainably managing marine commercial species “maximises the catch and food production”, thus contributing to the UN’s zero hunger goal. 

The figure below examines marine and coastal NbS and their feasibility and effectiveness in alleviating climate risks in the medium term. The weight of the outline surrounding boxes indicates confidence in the solution’s potential, based on observed evidence. Each solution’s feasibility and effectiveness are ranked by dots in blue and red respectively, based on its ability to support ecosystems and communities as they adapt.

Urban NbS

Carefully designed urban greening in cities and “well-functioning ecosystems can play a significant role in buffering cities, settlements and infrastructure from climate hazards at multiple scales”, the report states. 

Investing in “green and blue infrastructure” and natural area conservation in cities are “widely recognised as low-regret measures for disaster risk reduction and climate change adaptation”. From reducing temperature shocks and providing natural flood defences to physical and mental health co-benefits, urban NbS provide many “adaptation and resilience benefits”, the authors note. 

Street trees, green roofs, green walls and other urban vegetation are among the strategies it lists that can reduce extreme heat by cooling private and public spaces. 

Outdoor green spaces may also slightly reduce indoor heat risks and contribute to lower energy costs, it says. Studies assessed show that homes with shade trees “in cities where air conditioning systems are common can save over 30% of residential peak cooling demand”.

The report says “not all green schemes” in cities should be considered NbS, especially if they do not benefit biodiversity. 

It points to studies of how schemes could cause “green gentrification, which offers nature based solutions to the few”, increase water demand or public use. The report advises careful planning with equity consequences in mind, so that wealthy neighbourhoods do not benefit more than the poor. 

Wetland restoration close to settlements should be paired with mosquito control to safeguard public health, but is extremely effective at reducing toxicity and improving water filtration, the report says.

There is robust evidence that “urban parks and open spaces, forests, wetlands, green roofs and engineered stormwater treatment devices” reduce stormwater runoff, surface flooding, and contamination of runoff by pollutants. 

Similarly, authors are in high agreement that coastal ecosystems can reduce impacts of coastal flooding and storms in cities. For instance, vegetation and reefs can “dissipate wave energy”, reduce water levels and shoreline erosion, with “potential to save lives and prevent expensive property damage”. However, “coastal habitats also have limitations in their ability to protect coasts from extreme events”, including tsunamis.

Urban farming can serve as a NbS for food security and already does so for poor communities, the report notes, but land availability “can be further constrained by land-use history, including past industrial uses”. 

Approval session

Including the term “nature-based solutions” in the SPM was heavily contested during the SPM approval session. According to Third World Network, “developed countries led by France advocated for [NbS] as a measure to reduce climate risks to people, biodiversity and ecosystem services and to treat it on par with ecosystem-based adaptation”.

However, developing countries “led by South Africa” argued that the term was contentious. According to the Earth Negotiations Bulletin (ENB), South Africa, India and Ecuador “insisted that the NbS concept is highly problematic and that just because it exists in the literature does not mean it should be taken up by the IPCC”, calling for its removal or “not having it in Section C linked to adaptation”, as suggested by India. India reportedly said the term comes from a “European urbanised context” and that its problem was the word “solutions”, which “brushed the need for mitigation under the carpet”.

Eventually, “nature-based solutions” was negotiated to a footnote in the SPM. The SPM adds that the term is “the subject of ongoing debate, with concerns that it may lead to the misunderstanding that NbS on its own can provide a global solution to climate change”.

In addition, Argentina’s proposal to reference the Convention on Biological Diversity (CBD) in the footnote – set to negotiate a new agreement for nature this year – was opposed by the US, India and others, ENB says.

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14. What does the report say about climate-resilient development?

The link between climate change and sustainable development has “long been recognised and has been assessed in every WG2 report since AR3” in 2001, the report says. The concept of “climate-resilient development” was introduced in AR5 “to help assess development trajectories that include coordinated adaptation and mitigation actions aimed at reducing climate risk”.

The AR6 report devotes chapter 18 to the topic, along with dedicated sections within other chapters, “emphasising the need for integrative and transformative solutions within a sector or region that address the uneven distribution of climate risks among different groups and geographies”.

The authors define climate-resilient development as “a process of implementing greenhouse gas mitigation and adaptation solutions to support sustainable development for all”. They explain that pursuing climate action and sustainable development “in an integrated manner increases their effectiveness in enhancing human and ecological well-being”.

Climate-resilient development can “help build capacity” for mitigation and adaptation, the report says. For example, it has very high confidence that “incorporating clean energy generation, healthy diets from sustainable food systems, appropriate urban planning and transport, universal health coverage and social protection, can generate substantial health and wellbeing co-benefits”. It adds:

“Similarly, universal water and energy access can help to reduce poverty and improve well-being while making populations less vulnerable and more resilient to adverse climate impacts.”

There are “multiple possible pathways” to pursue climate-resilient development, the report says, which “involves confronting complex synergies and trade-offs”. It adds:

“Reconciling the costs, benefits and trade-offs associated with adaptation, mitigation and sustainable development interventions and how they are distributed among different populations and geographies is essential and challenging, but also creates the potential to pursue synergies that benefit human and ecological well-being.”

The figure below – from the SPM – illustrates how societal choices lead towards (pathways in green) or away from (pathways in red) climate-resilient development. Some choices have mixed outcomes, which are shown as pathways in yellow and orange.

The figure highlights that there is a “narrow and closing window of opportunity to make transformational changes to move towards and not away from development futures that are more climate-resilient and sustainable”, the authors note. The dotted lines indicate pathways that are “no longer available due to past societal choices and increasing temperatures”.

The authors note that “inadequate progress towards the Sustainable Development Goals (SDGs) by 2030 reduces climate-resilient development prospects”.

The report warns that current development trends along with the impacts of climate change “are leading away from, rather than toward, sustainable development”. There is moderate agreement and robust evidence for this conclusion, the report notes.

These trends include “rising income inequality, continued growth in greenhouse gas emissions, land use change, food and water insecurity, human displacement, and reversals of long-term increasing life expectancy trends in some nations”, the report says. In turn, these trends “contribute to worsening poverty, injustice and inequity, and environmental degradation”, the authors say, which can be further exacerbated through climate change “by undermining human and ecological well-being”. 

The SPM warns with high confidence that climate resilient development “is already challenging at current global warming levels”, adding:

“The prospects for climate resilient development will be further limited if global warming levels exceeds 1.5C (high confidence) and not be possible in some regions and sub-regions if the global warming level exceeds 2C (medium confidence).”

Opportunities for climate resilient development vary by location, the report says with very high confidence:

“Response to global greenhouse gas emissions trajectories, regional and local development pathways, climate risk exposure, socioeconomic and ecological vulnerability, and the local capacity to implement effective adaptation and greenhouse gas mitigation options, differ depending on local contexts and conditions.”

For example, it says, “underlying social and economic vulnerabilities in Australasia, exacerbate disadvantage among particular social groups and there is deep underinvestment in adaptation, given current and projected risks”.

Box 18.2 in the report highlights the “vision of climate-resilient development in Kenya” as a case study. The country’s government has a vision to “transform Kenya into a newly-industrialising, middle-income country providing a high quality of life to all its citizens in a clean and secure environment”.

A key element of this vision is the Lamu Port South Sudan Ethiopia project (LAPSSET), which aims to create a transport corridor connecting Kenya’s Lamu port with South Sudan and Ethiopia. The project consists of two elements: a 500-metre wide “infrastructure corridor” where the road, railway, pipelines, power transmission and other projects will be located, and an “economic corridor” of 50km on either side of the infrastructure corridor, which will contain “other industrial investments”, the report says.

Supporters of the project argue that it will help open up “poorly connected regions, enabling the development of pertinent economic sectors such as agriculture, livestock and energy, and supporting the attainment of a range of social goals made possible as the economy grows”, the report says.

However, it “remains controversial in its assumptions, not least because it is being promoted in the context of a highly complex and dynamic social, economic and biophysical setting”.

The interconnected nature of these different factors “intersect with LAPSSET in myriad ways”, the authors say: 

“For example, the implementation of LAPSSET may accentuate some trends, such as increases in land enclosure and a shift towards more urban and sedentary livelihoods. Conversely, the perceived threat LAPSSET could pose to pastoral lifestyles may lead to greater visibility, solidarity and strength of pastoralist institutions.”

Box 18.6 in the report describes how ecosystems play a “key role” in climate-resilient development, noting the importance of actions taken to mitigate climate change not compromising adaptation, biodiversity and human needs. This section also notes:

“Ecosystem protection and restoration, ecosystem-based adaptation (EbA) and nature-based solution (NbS) can lower climate risk to people and achieve multiple benefits including food and material provision, climate mitigation and social benefits.”

The report also has a “cross-chapter box” focusing on “gender, climate justice and transformative pathways”. It notes with high confidence that “gender and other social inequities (e.g., racial, ethnic, age, income, geographic location) compound vulnerability to climate change impacts”. 

Adaptation actions “do not automatically have positive outcomes for gender equality”, the authors note, and “efforts are needed to change unequal power dynamics and to foster inclusive decision making for climate adaptation to have a positive impact for gender equality”. 

In addition, the report notes with very high confidence that “there are very few examples of successful integration of gender and other social inequities in climate policies to address climate change vulnerabilities and questions of social justice”.

There is no set definition of what constitutes success for climate-resilient development, the report notes. Instead, achievement or success is “always a work in progress”, it says:

“It is a constant process of evaluating, valuing, acting and adjusting various options for mitigation, adaptation and sustainable development, shaped by societal values as well as contestations of those values.”

That said, if climate-resilient development is defined as “a process of implementing greenhouse gas mitigation and adaptation options to support sustainable development for all” then “this implies various potential criteria for success”, the authors note. Therefore, “the 17 United Nations’ SDGs provide a good (although limited) measure of progress”.

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15. What information about specific regions does the report contain?

The IPCC’s treatment of regional climate change information has changed notably since the first assessment report, evolving from a patchwork of case studies in early assessments towards more systematic coverage of regional issues in more recent reports.

The AR6 WG2 report contains seven chapters – comprising more than 1,000 pages – on regional climate information. In order of appearance, these are Africa, Asia, Australasia, Central and South America, Europe, North America and Small Islands. 

The report’s ”very strong regional focus” is one of the key developments since AR5, WG2 co-chair Dr Debra Roberts said at a press conference ahead of the report’s publication. She noted that “we’ve literally physically moved our regional chapters into the centre of the report”, adding that “they’ve become a keystone”.

These regional chapters highlight the current and future impacts of climate change for each of the seven regions, including the impacts on:

• Regional temperatures
• Extreme weather events
• Food and water security
• Migration
• Health and diseases
• The economy and livelihoods

In addition to regional chapters, the authors have written seven “cross-chapter papers” on different environments and ecosystems. These are:

• Biodiversity hotspots
• Cities and settlements by the sea
• Deserts, semi-arid regions and desertification
• Mediterranean region
• Mountains
• Polar regions
• Tropical forests

The cross-chapter papers have a similar format to the regional chapters – outlining the current and projected impact of climate change on the region, and discussing adaptation measures, often with an emphasis on Indigenous knowledge.

These papers are a new addition to the new WG2 report. The AR5 WG2 report contains short cross-chapter boxes on topics including “ocean acidification” and “building long-term

resilience from tropical cyclone disasters” – but these are short and not as focused on specific regions or environments.

The regional chapters also feature case studies. For example, the Australasia chapter includes a box entitled “The Great Barrier Reef in Crisis”, which states with high confidence that the world’s largest coral reef “is already severely impacted by climate change”. 

Meanwhile, the Europe chapter has a box on “Venice and its lagoon”. It notes that Venice and its lagoon are a UNESCO World Heritage Site, but says that floods are increasingly threatening the city:

“The frequency of floods affecting the city has increased from once per decade in the first half of the 20th century to 40 times per decade in the period 2010-2019.”

And the Asia chapter discusses the continent’s glaciers in depth. It states that glaciers in Asia provide water for 220 million people downstream and that shrinkage of the glaciers over 2006-16 has driven instability in the water supply – which it projects will worsen in the coming decades.

Meanwhile, the Africa chapter includes the figure below, which compares per-capita emissions between the seven regions and shows the overall change in emissions over 1990-2019.

The figure shows that per-capita emissions are the highest in Australasia, North America and Europe – although they have decreased in all three regions since 1990. It also shows that Asia has seen a slight increase in per-capita emissions over the past three decades, which has caused overall emissions to triple.

The Africa chapter emphasises – with high confidence – the inequality in historical emissions:

“Africa has contributed among the least to historical greenhouse gas emissions (GHG) responsible for anthropogenic climate change and has the lowest per capita GHG emissions of all regions currently.”

Regional chapters of the report also discuss adaptation actions taken so far and highlight the potential and need for future adaptation measures. 

The small island regional chapter has high confidence that small islands “present the most urgent need for investment in capacity building and adaptation strategies”. However, it adds:

“For many small islands, adaptation actions are often incremental and do not match the scale of extreme or compounding events (high confidence).

“Adaptation strategies are already being implemented on some small islands although barriers are encountered including inadequate up-to-date and locally relevant information, limited availability of finance and technology, lack of integration of Indigenous knowledge and local knowledge in adaptation strategies, and institutional constraints.”

The importance of Indigenous knowledge for adaptation is stressed in many of the regional chapters. For example, the African chapter states with high confidence that “the diversity of African Indigenous knowledge and local knowledge systems provide a rich foundation for adaptation actions at local scales“.

It adds that Africa is home to more than 30% of the world’s indigenous languages, which are “exceptionally rich in ecosystem-specific knowledge on biodiversity, soil systems and water”, and that “Indigenous languages hold great potential for more effective climate change communication and services that enable climate adaptation”.

Meanwhile, the Central and South American chapter highlights the importance of Indigenous knowledge for adaptation, stating that “research approaches that integrate Indigenous knowledge and local knowledge systems, with natural and social sciences, have increased since AR5”.

Many regional chapters also include sections on key scientific developments since AR5. For example, the Africa chapter highlights the rising confidence in the scientific community of observed and projected climate risks in the continent.

In addition, new developments in Asia are more focused on research into climate adaptation, the authors say. And the European chapter highlights the “substantial increase” in extreme event attribution.

The SPM also discusses regional information, stating with high confidence that “west-, central- and east Africa, south Asia, Central and South America, small island developing states and the Arctic” are “hotspots of high human vulnerability”. 

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