Introduction

The IPCC AR6 is still underway, but findings are beginning to come out. The Summary for Policymakers for Working Group I (WGI) on the Physical science Basis of climate change was released in August 2021 and while drafts are available, the chapters of the actual report are still being finalized. On February 28, 2022, the Summary for Policymakers for Working Group II (WGII) on Impacts, Adaptation, and Vulnerability was released. Note that the discussion below uses UK spelling.

Since AR5, the knowledge base on observed and projected impacts and risks generated by climate hazards, exposure and vulnerability has increased with impacts attributed to climate change and key risks identified across the report.

This report recognizes the interdependence of climate, ecosystems and biodiversity, and human societies and integrates knowledge more strongly across the natural, ecological, social and economic sciences than earlier IPCC assessments. The assessment of climate change impacts and risks as well as adaptation is set against concurrently unfolding non-climatic global trends e.g., biodiversity loss, overall unsustainable consumption of natural resources, land and ecosystem degradation, rapid urbanisation, human demographic shifts, social and economic inequalities and a pandemic.

Headline Statements

Impacts

Widespread, pervasive impacts to ecosystems, people, settlements, and infrastructure have resulted from observed increases in the frequency and intensity of climate and weather extremes, including hot extremes on land and in the ocean, heavy precipitation events, drought and fire weather. Increasingly since AR5, these observed impacts have been attributed to human-induced climate change, particularly through increased frequency and severity of extreme events. These include increased heat-related human mortality, warm-water coral bleaching and mortality, increased drought-related tree mortality, and observed increases in areas burned by wildfires. Adverse impacts from tropical cyclones, with related losses and damages, have increased due to sea-level rise and the increase in heavy precipitation. Impacts in natural and human systems from slow-onset processes such as ocean acidification, sea-level rise or regional decreases in precipitation have also been attributed to human-induced climate change.

Climate change has caused substantial damages, and increasingly, irreversible losses, in terrestrial, freshwater and coastal and open ocean marine ecosystems. Widespread deterioration of ecosystem structure and function, resilience and natural adaptive capacity, as well as shifts in seasonal timing have occurred due to climate change, with adverse socioeconomic consequences.

Approximately half of the species assessed globally have shifted polewards or, on land, also to higher elevations. Hundreds of local losses of species have been driven by increases in the magnitude of heat extremes, as well as mass mortality events on land and in the ocean and loss of kelp forests. Some losses are already irreversible, such as the first species extinctions driven by climate change. Other impacts are approaching irreversibility such as the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain and Arctic ecosystems driven by permafrost thaw.

Climate change, including increases in frequency and intensity of extremes, has reduced food and water security, hindering efforts to meet Sustainable Development Goals. Although overall agricultural productivity has increased, climate change has slowed this growth over the past 50 years globally, related negative impacts were mainly in mid- and low-latitude regions, but positive impacts occurred in some high latitude regions. Ocean warming and ocean acidification have adversely affected food production from shellfish aquaculture and fisheries in some oceanic regions.

Increasing weather and climate extreme events have exposed millions of people to acute food insecurity and reduced water security, with the largest impacts observed in many locations and/or communities in Africa, Asia, Central and South America, Small Islands and the Arctic. Jointly, sudden losses of food production and access to food compounded by decreased diet diversity have increased malnutrition in many communities, especially for Indigenous Peoples, small-scale food producers and low-income households, with children, elderly people and pregnant women particularly impacted. Roughly half of the world’s population currently experience severe water scarcity for at least some part of the year due to climatic and non-climatic drivers.

Climate change has adversely affected the physical health of people globally and the mental health of people in the assessed regions. Climate change impacts on health are mediated through natural and human systems, including economic and social conditions and disruptions. In all regions extreme heat events have resulted in human mortality and morbidity. The occurrence of climate-related food-borne and water-borne diseases has increased. The incidence of vector-borne diseases has increased from range expansion and/or increased reproduction of disease vectors. Animal and human diseases, including zoonoses, are emerging in new areas. Water and food-borne disease risks have increased regionally from climate-sensitive aquatic pathogens, including Vibrio spp., and from toxic substances from harmful freshwater cyanobacteria. Although diarrheal diseases have decreased globally, higher temperatures and increased rain and flooding have increased their occurrence, including cholera and other gastrointestinal infections. In assessed regions, some mental health challenges are associated with increasing temperatures, trauma from weather and climate extreme events, and loss of livelihoods and culture. Increased exposure to wildfire smoke, atmospheric dust, and aeroallergens has been associated with climate-sensitive cardiovascular and respiratory distress. Health services have been disrupted by extreme events such as floods.

In urban settings, observed climate change has caused impacts on human health, livelihoods and key infrastructure. Multiple climate- and non-climate hazards impact cities, settlements and infrastructure and sometimes coincide, magnifying damage. Hot extremes have intensified in cities, where they have also aggravated air pollution events and limited functioning of key infrastructure. Observed impacts are concentrated amongst the economically and socially marginalized urban residents. Infrastructures, including transportation, water, sanitation and energy systems, have been compromised by extreme and slow-onset events, with resulting economic losses, disruptions of services and impacts to wellbeing.

Overall adverse economic impacts attributable to climate change, including slow-onset and extreme weather events, have been increasingly identified. Some positive economic effects have been identified in regions that have benefited from lower energy demand as well as comparative advantages in agricultural markets and tourism. Economic damages from climate change have been detected in climate-exposed sectors, with regional effects to agriculture, forestry, fishery, energy, and tourism, and through outdoor labor productivity. Some extreme weather events, such as tropical cyclones, have reduced economic growth in the short term. Non-climatic factors including some patterns of settlement, and siting of infrastructure have contributed to the exposure of more assets to extreme climate hazards increasing the magnitude of the losses. Individual livelihoods have been affected through changes in agricultural productivity, impacts on human health and food security, destruction of homes and infrastructure, and loss of property and income, with adverse effects on gender and social equity.

Climate change is contributing to humanitarian crises where climate hazards interact with high vulnerability. Climate and weather extremes are increasingly driving displacement in all regions, with Small Island States disproportionately affected. Flood and drought-related acute food insecurity and malnutrition have increased in Africa and Central and South America. While non-climatic factors are the dominant drivers of existing intrastate violent conflicts, in some assessed regions extreme weather and climate events have had a small, adverse impact on their length, severity or frequency, but the statistical association is weak. Through displacement and involuntary migration from extreme weather and climate events, climate change has generated and perpetuated vulnerability.

Vulnerabilities

Vulnerability of ecosystems and people to climate change differs substantially among and within regions, driven by patterns of intersecting socioeconomic development, unsustainable ocean and land use, inequity, marginalization, historical and ongoing patterns of inequity such as colonialism, and governance. Approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change.

A high proportion of species is vulnerable to climate change. Human and ecosystem vulnerability are interdependent. Current unsustainable development patterns are increasing exposure of ecosystems and people to climate hazards.

There is increasing evidence that degradation and destruction of ecosystems by humans increases the vulnerability of people. Unsustainable land-use and land-cover change, unsustainable use of natural resources, deforestation, loss of biodiversity, pollution, and their interactions, adversely affect the capacities of ecosystems, societies, communities and individuals to adapt to climate change. Loss of ecosystems and their services has cascading and long-term impacts on people globally, especially for Indigenous Peoples and local communities who are directly dependent on ecosystems, to meet basic needs.

Non-climatic human-induced factors exacerbate current ecosystem vulnerability to climate change. Globally, and even within protected areas, unsustainable use of natural resources, habitat fragmentation, and ecosystem damage by pollutants increase ecosystem vulnerability to climate change. Globally, less than 15% of the land, 21% of the freshwater and 8% of the ocean are protected areas. In most protected areas, there is insufficient stewardship to contribute to reducing damage from, or increasing resilience to, climate change.

Projected climate change, combined with non-climatic drivers, will cause loss and degradation of much of the world’s forests, coral reefs and low-lying coastal wetlands. While agricultural development contributes to food security, unsustainable agricultural expansion, driven in part by unbalanced diets, increases ecosystem and human vulnerability and leads to competition for land and/or water resources.

Regions and people with considerable development constraints have high vulnerability to climatic hazards. Global hotspots of high human vulnerability are found particularly in West, Central and East Africa, South Asia, Central and South America, Small Island Developing States and the Arctic. Vulnerability is higher in locations with poverty, governance challenges and limited access to basic services and resources, violent conflict and high levels of climate-sensitive livelihoods (e.g., smallholder farmers, pastoralists, fishing communities). Vulnerability at different spatial levels is exacerbated by inequity and marginalization linked to gender, ethnicity, low income or combinations thereof, especially for many Indigenous Peoples and local communities.

Global warming, reaching 1.5°C in the near term, would cause unavoidable increases in multiple climate hazards and present multiple risks to ecosystems and humans. The level of risk will depend on concurrent near-term trends in vulnerability, exposure, level of socioeconomic development and adaptation. Near-term actions that limit global warming to close to 1.5°C would substantially reduce projected losses and damages related to climate change in human systems and ecosystems, compared to higher warming levels, but cannot eliminate them all.

Beyond 2040 and depending on the level of global warming, climate change will lead to numerous risks to natural and human systems. For 127 identified key risks, assessed mid- and long-term impacts are up to multiple times higher than currently observed. The magnitude and rate of climate change and associated risks depend strongly on near-term mitigation and adaptation actions, and projected adverse impacts and related losses and damages escalate with every increment of global warming.

Biodiversity loss and degradation, and damages to and transformation of ecosystems, are already key risks for every region due to past global warming and will continue to escalate with every increment of global warming. In terrestrial ecosystems, 3 to 14% of species assessed will likely face very high risk of extinction at 1.5°C of global warming, increasing from a range of 3 to 18% at 2°C, 3 to 29% at 3°C, 3 to 39% at 4°, and 3 to 48% at 5°C. In ocean and coastal ecosystems, risk of biodiversity loss ranges between moderate and very high by 1.5°C of global warming and is moderate to very high by 2°C but with more ecosystems at high and very high risk, and increases to high to very high across most ocean and coastal ecosystems by 3°C. Very high extinction risk for endemic species in biodiversity hotspots is projected to at least double from 2% between 1.5°C and 2°C of global warming and to increase at least tenfold if warming rises from 1.5°C to 3°C.

Risks in physical water availability and water-related hazards will continue to increase by the mid to long term in all assessed regions, with greater risk at higher global warming levels. At approximately 2°C global warming, snowmelt water availability for irrigation is projected to decline in some snowmelt-dependent river basins by up to 20%, and global glacier mass loss of 18 ± 13% is projected to diminish water availability for agriculture, hydropower, and human settlements in the mid to long term, with these changes projected to double with 4°C of global warming. In small islands, groundwater availability is threatened by climate change. Changes to streamflow magnitude, timing and associated extremes are projected to adversely impact freshwater ecosystems in many watersheds by the mid to long term across all assessed scenarios.

Projected increases in direct flood damages are higher by 1.4 to 2 times at 2°C and 2.5 to 3.9 times at 3°C compared to 1.5°C global warming without adaptation. At global warming of 4°C, approximately 10% of the global land area is projected to face increases in both extreme high and low river flows in the same location, with implications for planning for all water-use sectors. Challenges for water management will be exacerbated in the near, mid and long term, depending on the magnitude, rate and regional details of future climate change and will be particularly challenging for regions with constrained resources for water management.

Climate change will increasingly put pressure on food production and access, especially in vulnerable regions, undermining food security and nutrition. Increases in frequency, intensity and severity of droughts, floods and heatwaves, and continued sea-level rise will increase risks to food security in vulnerable regions from moderate to high between 1.5°C and 2°C of global warming, with no or low levels of adaptation. At 2°C or higher of global warming in the mid term, food security risks due to climate change will be more severe, leading to malnutrition and micro-nutrient deficiencies, concentrated in Sub-Saharan Africa, South Asia, Central and South America and Small Islands.

Global warming will progressively weaken soil health and ecosystem services such as pollination, increase pressure from pests and diseases, and reduce marine animal biomass, undermining food productivity in many regions on land and in the ocean. At 3°C or higher of global warming in the long term, areas exposed to climate-related hazards will expand substantially compared with 2°C or lower of global warming, exacerbating regional disparity in food security risks.

Climate change and related extreme events will significantly increase ill health and premature deaths from the near to long term. Globally, population exposure to heatwaves will continue to increase with additional warming, with strong geographical differences in heat-related mortality without additional adaptation. Climate-sensitive food-borne, water-borne, and vector-borne disease risks are projected to increase under all levels of warming without additional adaptation. In particular, dengue risk will increase with longer seasons and a wider geographic distribution in Asia, Europe, Central and South America and sub-Saharan Africa, potentially putting additional billions of people at risk by the end of the century. Mental health challenges, including anxiety and stress, are expected to increase under further global warming in all assessed regions, particularly for children, adolescents, elderly, and those with underlying health conditions.

Climate-change risks to cities, settlements and key infrastructure will rise rapidly in the mid- and long-term with further global warming, especially in places already exposed to high temperatures, along coastlines, or with high vulnerabilities. Globally, population change in low-lying cities and settlements will lead to approximately a billion people projected to be at risk from coastal-specific climate hazards in the mid-term under all scenarios, including in Small Islands. The population potentially exposed to a 100-year coastal flood is projected to increase by about 20% if global mean sea level rises by 0.15m relative to the 2020 global mean; this exposed population doubles at a 0.75m rise in mean sea level and triples at 1.4m without population change and additional adaptation. Sea-level rise poses an existential threat for some Small Islands and some low-lying coasts. By 2100 the value of global assets within the future 1-in-100-year coastal floodplains is projected to be between US$7.9 and US$12.7 trillion (2011 value) under RCP4.5, rising to between US$8.8 and US$14.2 trillion under RCP8.5.

Costs for maintenance and reconstruction of urban infrastructure, including building, transportation, and energy, will increase with global warming. The associated functional disruptions are projected to be substantial particularly for cities, settlements and infrastructure located on permafrost in cold regions and on coasts.

Projected estimates of global aggregate net economic damages generally increase non-linearly with global warming. The wide range of global estimates, and the lack of comparability between methodologies, does not enable identification of a robust range of estimates. Significant regional variation in aggregate economic damages from climate change is projected with estimated economic damages per capita for developing countries often higher as a fraction of income. Economic damages, including both those represented and those not represented in economic markets, are projected to be lower at 1.5°C than at 3°C or higher.

Climate-change impacts and risks are becoming increasingly complex and more difficult to manage. Multiple climate hazards will occur simultaneously, and multiple climatic- and non-climatic risks will interact, resulting in compounding overall risk and risks cascading across sectors and regions. Some responses to climate change result in new impacts and risks.

Adaptation

Progress in adaptation planning and implementation has been observed across all sectors and regions, generating multiple benefits. However, adaptation progress is unevenly distributed and ha discernible gaps. Many initiatives prioritize immediate and near-term climate risk reduction which reduces the opportunity for transformational adaptation.

Despite progress, adaptation gaps exist between current levels of adaptation and levels needed to respond to impacts and reduce climate risks. Most observed adaptation is fragmented, small in scale, incremental, sector-specific, designed to respond to current impacts or near-term risks, and focused more on planning rather than implementation. Observed adaptation is unequally distributed across regions, and gaps are partially driven by widening disparities between the estimated costs of adaptation and documented finance allocated to adaptation. The largest adaptation gaps exist among lower income population groups. At current rates of adaptation planning and implementation the adaptation gap will continue to grow. As adaptation options often have long implementation times, long-term planning and accelerated implementation, particularly in the next decade, is important to close adaptation gaps, recognising that constraints remain for some regions.

There are feasible and effective adaptation options which can reduce risks to people and nature. The feasibility of implementing adaptation options in the near term differs across sectors and regions. The effectiveness of adaptation to reduce climate risk is documented for specific contexts, sectors and regions (high confidence) and will decrease with increasing warming. Integrated, multi-sectoral solutions that address social inequities, differentiate responses based on climate risk and cut across systems increase the feasibility and effectiveness of adaptation in multiple sectors.

Interactions between changing urban form, exposure and vulnerability can create climate-change-induced risks and losses for cities and settlements. However, the global trend of urbanisation also offers a critical opportunity in the near term, to advance climate resilient development. Integrated, inclusive planning and investment in everyday decision making about urban infrastructure, including social, ecological and grey/physical infrastructures, can significantly increase the adaptive capacity of urban and rural settlements. Equitable outcomes contribute to multiple benefits for health and well-being and ecosystem services, including for Indigenous Peoples and marginalised and vulnerable communities. Climate-resilient development in urban areas also supports adaptive capacity in more rural places through maintaining peri-urban supply chains of goods and services and financial flows. Coastal cities and settlements play an especially important role in advancing climate-resilient development.

Safeguarding biodiversity and ecosystems is fundamental to climate-resilient development, in light of the threats climate change poses to them and their roles in adaptation and mitigation. Recent analyses, drawing on a range of lines of evidence, suggest that maintaining the resilience of biodiversity and ecosystem services at a global scale depends on effective and equitable conservation of approximately 30% to 50% of Earth’s land, freshwater and ocean areas, including currently near-natural ecosystems.

Climate-resilient development is already challenging at current global-warming levels. The prospects for climate-resilient development will be further limited if global warming exceeds 1.5°C and will not be possible in some regions and sub-regions if global warming exceeds 2°C. Climate-resilient development is most constrained in regions/subregions in which climate impacts and risks are already advanced, including low-lying coastal cities and settlements, small islands, deserts, mountains and polar regions.