Editing IPCC:AR6/SYR/Longer-Report (section)

==== 2.1.2. Observed Climate System Changes and Impacts to Date ====

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'''It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred (Table 2.1).''' The scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system are unprecedented over many centuries to many thousands of years. It is ''very likely'' that GHG emissions were the main driver '''[[#footnote-083|74]]''' of tropospheric warming and ''extremely likely'' that human-caused stratospheric ozone depletion was the main driver of stratospheric cooling between 1979 and the mid-1990s. It is ''virtually certain'' that the global upper ocean (0-700m) has warmed since the 1970s and ''extremely likely'' that human influence is the main driver. Ocean warming accounted for 91% of the heating in the climate system, with land warming, ice loss and atmospheric warming accounting for about 5%, 3% and 1%, respectively ( ''high confidence'' ). Global mean sea level increased by 0.20 [0.15 to 0.25] m between 1901 and 2018. The average rate of sea level rise was 1.3 [0.6 to 2.1]mm yr ''-1'' between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm yr ''-1'' between 1971 and 2006, and further increasing to 3.7 [3.2 to –4.2] mm yr ''-1'' between 2006 and 2018 ( ''high confidence'' ). Human influence was ''very likely'' the main driver of these increases since at least 1971 (Figure 3.4). Human influence is ''very likely'' the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice area between 1979–1988 and 2010–2019. Human influence has also ''very likely'' contributed to decreased Northern Hemisphere spring snow cover and surface melting of the Greenland ice sheet. It is ''virtually'' certain that human-caused CO 2 emissions are the main driver of current global acidification of the surface open ocean. { ''WGI SPM A.1,'' . ''WGI SPM A.1.3, WGI SPM A.1.5, WGI SPM A.1.6, WG1 SPM A1.7, WGI SPM A.2, WG1.SPM A.4.2; SROCC SPM.A.1, SROCC SPM A.2'' }

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'''Table 2.1: Assessment of observed changes in large-scale indicators of mean climate across climate system components, and their attribution to human influence.''' The colour coding indicates the assessed confidence in / likelihood '''[[#footnote-081|76]]''' of the observed change and the human contribution as a driver or main driver (specified in that case) where available (see colour key). Otherwise, explanatory text is provided. { ''WGI Table TS.1'' }

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'''Human-caused climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has strengthened since AR5 (Figure 2.3).''' It is ''virtually'' certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s (Figure 2.3), while cold extremes (including cold waves) have become less frequent and less severe, with ''high confidence'' that human-caused climate change is the main driver of these changes. Marine heatwaves have approximately doubled in frequency since the 1980s ( ''high confidence'' ), and human influence has ''very likely'' contributed to most of them since at least 2006. The frequency and intensity of heavy precipitation events have increased since the 1950s over most land areas for which observational data are sufficient for trend analysis ( ''high confidence'' ), and human-caused climate change is ''likely'' the main driver (Figure 2.3). Human-caused climate change has contributed to increases in agricultural and ecological droughts in some regions due to increased land evapotranspiration ( ''medium confidence'' ) (Figure 2.3). It is ''likely'' that the global proportion of major (Category 3–5) tropical cyclone occurrence has increased over the last four decades. { ''WGI SPM A.3, WGI SPM A3.1, WGI SPM A3.2; WGI SPM A3.4; SRCCL SPM.A.2.2; SROCC SPM. A.2'' }

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'''Figure 2.3: Both vulnerability to current climate extremes and historical contribution to climate change are highly heterogeneous with many of those who have least contributed to climate change to date being most vulnerable to its impacts. Panel (a)''' The IPCC AR6 WGI inhabited regions are displayed as hexagons with identical size in their approximate geographical location (see legend for regional acronyms). All assessments are made for each region as a whole and for the 1950s to the present. Assessments made on different time scales or more local spatial scales might differ from what is shown in the figure. The colours in each panel represent the four outcomes of the assessment on observed changes. Striped hexagons (white and light-grey) are used where there is ''low agreement'' in the type of change for the region as a whole, and grey hexagons are used when there is limited data and/or literature that prevents an assessment of the region as a whole. Other colours indicate at least ''medium confidence'' in the observed change. The confidence level for the human influence on these observed changes is based on assessing trend detection and attribution and event attribution literature, and it is indicated by the number of dots: three dots for ''high confidence'' , two dots for ''medium confidence'' and one dot for ''low confidence'' (single, filled dot: ''limited agreemen'' t; single, empty dot: ''limited evidence'' ). For hot extremes, the evidence is mostly drawn from changes in metrics based on daily maximum temperatures; regional studies using other indices (heatwave duration, frequency and intensity) are used in addition. For heavy precipitation, the evidence is mostly drawn from changes in indices based on one-day or five-day precipitation amounts using global and regional studies. Agricultural and ecological droughts are assessed based on observed and simulated changes in total column soil moisture, complemented by evidence on changes in surface soil moisture, water balance ( precipitation minus evapotranspiration) and indices driven by precipitation and atmospheric evaporative demand. '''Panel (b)''' shows the average level of vulnerability amongst a country’s population against 2019 CO 2 -FFI emissions per- capita per country for the 180 countries for which both sets of metrics are available. Vulnerability information is based on two global indicator systems, namely INFORM and World Risk Index. Countries with a relatively low average vulnerability often have groups with high vulnerability within their population and vice versa. The underlying data includes, for example, information on poverty, inequality, health care infrastructure or insurance coverage. '''Panel (c)''' Observed impacts on ecosystems and human systems attributed to climate change at global and regional scales. Global assessments focus on large studies, multi-species, meta-analyses and large reviews. Regional assessments consider evidence on impacts across an entire region and do not focus on any country in particular. For human systems, the direction of impacts is assessed and both adverse and positive impacts have been observed e.g., adverse impacts in one area or food item may occur with positive impacts in another area or food item (for more details and methodology see WGII SMTS.1). Physical water availability includes balance of water available from various sources including ground water, water quality and demand for water. Global mental health and displacement assessments reflect only assessed regions. Confidence levels reflect the assessment of attribution of the observed impact to climate change. ''{ WGI Figure SPM.3, Table TS.5, Interactive Atlas; WGII Figure SPM.2, WGII SMTS.1, WGII 8.3.1, Figure 8.5; ; WGIII 2.2.3 }''

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'''Climate change has caused substantial damages, and increasingly irreversible''' '''[[#footnote-082|75]] losses, in terrestrial, freshwater, cryospheric and coastal and open ocean ecosystems''' '''''(''''' '''''high confidence). The extent and magnitude of climate change impacts are larger than estimated in previous assessments (''''' '''''high confidence)''''' . Approximately half of the species assessed globally have shifted polewards or, on land, also to higher elevations ( ''very high confidence'' ). Biological responses including changes in geographic placement and shifting seasonal timing are often not sufficient to cope with recent climate change. ( ''very high confidence'' ). Hundreds of local losses of species have been driven by increases in the magnitude of heat extremes ( ''high confidence'' ) and mass mortality events on land and in the ocean ( ''very high confidence'' ). Impacts on some ecosystems are approaching irreversibility such as the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain ( ''medium confidence'' ) and Arctic ecosystems driven by permafrost thaw ( ''high confidence'' ). Impacts in ecosystems from slow-onset processes such as ocean acidification, sea level rise or regional decreases in precipitation have also been attributed to human-caused climate change ( ''high confidence'' ). Climate change has contributed to desertification and exacerbated land degradation, particularly in low lying coastal areas, river deltas, drylands and in permafrost areas ( ''high confidence'' ). Nearly 50% of coastal wetlands have been lost over the last 100 years, as a result of the combined effects of localised human pressures, sea level rise, warming and extreme climate events ( ''high confidence'' ). { ''WGII SPM B.1.1, WGII SPM B.1.2, WGII Figure SPM.2.A, WGII TS.B.1; SRCCL SPM A.1.5, SRCCL SPM A.2, SRCCL SPM A.2.6, SRCCL Figure SPM.1; SROCC SPM A.6.1, SROCC SPM, A.6.4, SROCC SPM A.7'' } .

'''Climate change has reduced food security and affected water security due to warming, changing precipitation patterns, reduction and loss of cryospheric elements, and greater frequency and intensity of climatic extremes, thereby hindering efforts to meet Sustainable Development Goals (''' '''''high confidence).''''' Although overall agricultural productivity has increased, climate change has slowed this growth in agricultural productivity over the past 50 years globally ( ''medium confidence'' ), with related negative crop yield impacts mainly recorded in mid- and low latitude regions, and some positive impacts in some high latitude regions ( ''high confidence'' ). Ocean warming in the 20th century and beyond has contributed to an overall decrease in maximum catch potential ( ''medium confidence'' ), compounding the impacts from overfishing for some fish stocks ( ''high confidence'' ). Ocean warming and ocean acidification have adversely affected food production from shellfish aquaculture and fisheries in some oceanic regions ( ''high confidence'' ). Current levels of global warming are associated with moderate risks from increased dryland water scarcity ( ''high confidence'' ). Roughly half of the world’s population currently experiences severe water scarcity for at least some part of the year due to a combination of climatic and non-climatic drivers ( ''medium confidence'' ) (Figure 2.3). Unsustainable agricultural expansion, driven in part by unbalanced diets '''[[#footnote-080|77]]''' , increases ecosystem and human vulnerability and leads to competition for land and/or water resources ( ''high confidence'' ). Increasing weather and climate extreme events have exposed millions of people to acute food insecurity '''[[#footnote-079|78]]''' and reduced water security, with the largest impacts observed in many locations and/or communities in Africa, Asia, Central and South America, LDCs, Small Islands and the Arctic, and for small-scale food producers, low-income households and Indigenous Peoples globally ( ''high confidence'' ). { ''WGII SPM B.1.3, WGII SPM.B.2.3, WGII Figure SPM.2, WGII TS B.2.3, WGII TS Figure TS. 6; SRCCL SPM A.2.8, SRCCL SPM A.5.3; SROCC SPM A.5.4., SROCC SPMA.7.1, SROCC SPM A.8.1, SROCC Figure SPM.2'' } .

'''In urban settings, climate change has caused adverse impacts on human health, livelihoods and key infrastructure (''' '''''high confidence)''''' '''.''' Hot extremes including heatwaves have intensified in cities ( ''high confidence'' ), where they have also worsened air pollution events. ( ''medium confidence'' ) and limited functioning of key infrastructure ( ''high confidence'' ). Urban infrastructure, including transportation, water, sanitation and energy systems have been compromised by extreme and slow-onset events '''[[#footnote-078|79]]''' , with resulting economic losses, disruptions of services and impacts to well-being ( ''high confidence'' ). Observed impacts are concentrated amongst economically and socially marginalised urban residents, e.g., those living in informal settlements. ( ''high confidence'' ). Cities intensify human-caused warming locally ( ''very high confidence'' ), while urbanisation also increases mean and heavy precipitation over and/or downwind of cities ( ''medium confidence'' ) and resulting runoff intensity ( ''high confidence'' ). { ''WGI SPM C.2.6; WGII SPM B.1.5, WGII Figure TS.9, WGII 6 ES'' }

'''Climate change has adversely affected human physical health globally and mental health in assessed regions (''' '''''very high confidence), and is contributing to humanitarian crises where climate hazards interact with high vulnerability (''''' '''''high confidence).''''' In all regions increases in extreme heat events have resulted in human mortality and morbidity ( ''very high confidence'' ). The occurrence of climate-related food-borne and water-borne diseases has increased ( ''very high confidence'' ). The incidence of vector-borne diseases has increased from range expansion and/or increased reproduction of disease vectors ( ''high confidence'' ). Animal and human diseases, including zoonoses, are emerging in new areas ( ''high confidence'' ). In assessed regions, some mental health challenges are associated with increasing temperatures ( ''high confidence'' ), trauma from extreme events ( ''very high confidence'' ), and loss of livelihoods and culture ( ''high confidence'' ). (Figure 2.3). Climate change impacts on health are mediated through natural and human systems, including economic and social conditions and disruptions ( ''high confidence'' ). Climate and weather extremes are increasingly driving displacement in Africa, Asia, North America ( ''high confidence'' ), and Central and South America. ( ''medium confidence'' ). (Figure 2.3), with small island states in the Caribbean and South Pacific being disproportionately affected relative to their small population size ( ''high confidence'' ). Through displacement and involuntary migration from extreme weather and climate events, climate change has generated and perpetuated vulnerability ( ''medium confidence'' ). { ''WGII SPM B.1.4, WGII SPM B.1.7'' }

'''Human influence has''' '''''likely increased the chance of compound extreme events''''' '''[[#footnote-077|80]] since the 1950s. Concurrent and repeated climate hazards have occurred in all regions, increasing impacts and risks to health, ecosystems, infrastructure, livelihoods and food (''' '''''high confidence).''''' Compound extreme events include increases in the frequency of concurrent heatwaves and droughts ( ''high confidence'' ); fire weather in some regions ( ''medium confidence'' ); and compound flooding in some locations ( ''medium confidence'' ). Multiple risks interact, generating new sources of vulnerability to climate hazards, and compounding overall risk ( ''high confidence'' ). Compound climate hazards can overwhelm adaptive capacity and substantially increase damage ( ''high confidence'' ). { ''WGI SPM A.3.5; WGII SPM. B.5.1, WGII TS.C.11.3'' }

'''Economic impacts attributable to climate change are increasingly affecting peoples’ livelihoods and are causing economic and societal impacts across national boundaries (''' '''''high confidence)''''' '''.''' 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 labour productivity ( ''high confidence'' ) with some exceptions of positive impacts in regions with low energy demand and comparative advantages in agricultural markets and tourism. ( ''high confidence'' ). 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 ( ''high confidence'' ). Tropical cyclones have reduced economic growth in the short-term ( ''high confidence'' ). Event attribution studies and physical understanding indicate that human-caused climate change increases heavy precipitation associated with tropical cyclones ( ''high confidence'' ). Wildfires in many regions have affected built assets, economic activity, and health ( ''medium'' to ''high confidence'' ). In cities and settlements, climate impacts to key infrastructure are leading to losses and damages across water and food systems, and affect economic activity, with impacts extending beyond the area directly impacted by the climate hazard. ( ''high confidence'' ). { ''WGI SPM A.3.4; WGII SPM B.1.6, WGII SPM B.5.2, WGII SPM B.5.3'' } .

'''Climate change has caused widespread adverse impacts and related losses and damages to nature and people (''' '''''high confidence).''''' Losses and damages are unequally distributed across systems, regions and sectors ( ''high confidence'' ). Cultural losses, related to tangible and intangible heritage, threaten adaptive capacity and may result in irrevocable losses of sense of belonging, valued cultural practices, identity and home, particularly for Indigenous Peoples and those more directly reliant on the environment for subsistence. ( ''medium confidence'' ). For example, changes in snow cover, lake and river ice, and permafrost in many Arctic regions, are harming the livelihoods and cultural identity of Arctic residents including Indigenous populations ( ''high confidence'' ). Infrastructure, 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 well-being ( ''high confidence'' ). { ''WGII SPM B.1, WGII SPM B.1.2, WGII SPM.B.1.5, WGII SPM C.3.5, WGII TS.B.1.6; SROCC SPM A.7.1'' }

'''Across sectors and regions, the most vulnerable people and systems have been disproportionately affected by the impacts of climate change''' '''''(''''' '''''high confidence).''''' LDCs and SIDS who have much lower per capita emissions (1.7 tCO 2 -eq, 4.6 tCO 2 -eq, respectively) than the global average (6.9 tCO 2 -eq) excluding CO 2 -LULUCF, also have high vulnerability to climatic hazards, with global hotspots of high human vulnerability observed in West-, Central- and East Africa, South Asia, Central and South America, SIDS and the Arctic ( ''high confidence'' ). Regions and people with considerable development constraints have high vulnerability to climatic hazards ( ''high confidence'' ). 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) ( ''high confidence'' ). Vulnerability at different spatial levels is exacerbated by inequity and marginalisation linked to gender, ethnicity, low income or combinations thereof ( ''high confidence'' ), especially for many Indigenous Peoples and local communities ( ''high confidence'' ). Approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change ( ''high confidence'' ). Between 2010 and 2020, human mortality from floods, droughts and storms was 15 times higher in highly vulnerable regions, compared to regions with very low vulnerability ( ''high confidence'' ). In the Arctic and in some high mountain regions, negative impacts of cryosphere change have been especially felt among Indigenous Peoples ( ''high confidence'' ). Human and ecosystem vulnerability are interdependent ( ''high confidence'' ). Vulnerability of ecosystems and people to climate change differs substantially among and within regions ( ''very high confidence'' ), driven by patterns of intersecting socio-economic development, unsustainable ocean and land use, inequity, marginalisation, historical and ongoing patterns of inequity such as colonialism, and governance '''[[#footnote-076|81]]''' ( ''high confidence'' ). { ''WGII SPM B.1, WGII SPM B.2, WGII SPM B.2.4; WGIII SPM B.3.1; SROCC SPM A.7.1, SROCC SPM A.7.2'' }

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