9
SPM
Summary for Policymakers
Observed Impacts from Climate Change
28 Attribution is defined as the process of evaluating the relative contributions of multiple causal factors to a change or event with an assessment of confidence. {Annex II Glossary, CWGB ATTRIB}
29 Impacts of climate change are caused by slow onset and extreme events. Slow onset events are described among the climatic-impact drivers of the WGI AR6 and refer to the risks and impacts
associated with e.g., increasing temperature means, desertification, decreasing precipitation, loss of biodiversity, land and forest degradation, glacial retreat and related impacts, ocean acidification,
sea level rise and salinization (https://interactive-atlas.ipcc.ch).
30 Acute food insecurity can occur at any time with a severity that threatens lives, livelihoods or both, regardless of the causes, context or duration, as a result of shocks risking determinants of food
security and nutrition, and used to assess the need for humanitarian action.
B.1 Human-induced climate change, including more frequent and intense extreme events, has caused widespread adverse
impacts and related losses and damages to nature and people, beyond natural climate variability. Some development and
adaptation efforts have reduced vulnerability. Across sectors and regions the most vulnerable people and systems are ob-
served to be disproportionately affected. The rise in weather and climate extremes has led to some irreversible impacts as
natural and human systems are pushed beyond their ability to adapt. (high confidence) (FigureSPM.2) {TS B.1, FigureTS.5,
1.3, 2.3, 2.4, 2.6, 3.3, 3.4, 3.5, 4.2, 4.3, 5.2, 5.12, 6.2, 7.2, 8.2, 9.6, 9.8, 9.10, 9.11, 10.4, 11.3, 12.3, 12.4, 13.10, 14.4, 14.5,
15.3, 16.2, CCP1.2, CCP3.2, CCP4.1, CCP5.2, CCP6.2, CCP7.2, CCP7.3, CCB DISASTER, CCB EXTREMES, CCB ILLNESS, CCB
MIGRATE, CCB NATURAL, CCB SLR}
B.1.1 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 (high confidence).Increasingly since AR5, these observed impacts have been attributed
28
to human-induced
climate change particularly through increased frequency and severity of extreme events. These include increased heat-related human
mortality (medium confidence), warm-water coral bleaching and mortality (high confidence), and increased drought-related tree
mortality (high confidence). Observed increases in areas burned by wildfires have been attributed to human-induced climate change
in some regions (medium to high confidence). Adverse impacts from tropical cyclones, with related losses and damages
19
, have
increased due to sea level rise and the increase in heavy precipitation (medium confidence). Impacts in natural and humansystems
from slow-onset processes
29
such asocean acidification, sea level rise or regional decreases in precipitationhave also been attributed
to human induced climate change (high confidence). {1.3, 2.3, 2.4, 2.5, 3.2, 3.4, 3.5, 3.6, 4.2, 5.2, 5.4, 5.6, 5.12, 7.2, 9.6, 9.7, 9.8, 9.11,
11.3, Box11.1, Box11.2, Table11.9, 12.3, 12.4, 13.3, 13.5, 13.10, 14.2, 14.5, 15.7, 15.8, 16.2, CCP1.2, CCP2.2, BoxCCP5.1, CCP7.3,
CCB DISASTER, CCB EXTREME, CCB ILLNESS, WGI AR6 SPM.3, WGI AR6 9, WGI AR6 11.3–11.8, SROCC Chapter4}
B.1.2 Climate change has caused substantial damages, and increasingly irreversible losses, in terrestrial, freshwater andcoastal and open
ocean marine ecosystems (high confidence). The extent and magnitude of climate change impacts are larger than estimated in previous
assessments (high confidence). 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 (high confidence), with adverse socioeconomic consequences
(high confidence). Approximately half of the species assessed globally have shiftedpolewards or,on land, also to higher elevations
(very high confidence). Hundreds of local losses of species have been driven by increases in the magnitude of heat extremes (high
confidence), as well as mass mortality events on land and in the ocean (very high confidence) and loss of kelp forests (high confidence).
Some losses are already irreversible, such as the first species extinctions driven by climate change (medium confidence). Other impacts
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). (FigureSPM.2a). { TS B.1,
FigureTS.5, 2.3, 2.4, 3.4, 3.5, 4.2, 4.3, 4.5, 9.6, 10.4, 11.3, 12.3, 12.8, 13.3, 13.4, 13.10, 14.4, 14.5, 14.6, 15.3, 16.2, CCP1.2, CCP3.2,
CCP4.1, CCP5.2, FigureCCP5.4, CCP6.1, CCP6.2, CCP7.2, CCP7.3, CCB EXTREMES, CCB ILLNESS, CCB MOVING PLATE, CCB NATURAL,
CCB PALEO, CCB SLR, SROCC 2.3}
B.1.3 Climate change including increases in frequency and intensity of extremes have reduced food and water security, hindering efforts
to meet Sustainable Development Goals (high confidence). Although overall agricultural productivity has increased, climate change
has slowed this growth over the past 50years globally (medium confidence), related negative impacts were mainly in mid- and low
latitude regions but positive impacts occurred in some high latitude regions (high confidence). Ocean warming and ocean acidification
have adversely affected food production from shellfish aquaculture and fisheries in some oceanic regions (high confidence). Increasing
weather and climate extreme events have exposed millions of people to acute food insecurity
30
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
(high confidence). Jointly, sudden losses of food production and access to food compounded by decreased diet diversity have increased
malnutrition in many communities (high confidence), especially for Indigenous Peoples, small-scale food producers and low-income
households (high confidence), with children, elderly people and pregnant women particularly impacted (high confidence). 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 (medium confidence). (FigureSPM.2b) {3.5, 4.3, 4.4, Box4.1, 5.2, 5.4, 5.8, 5.9, 5.12, 7.1, 7.2, 9.8, 10.4, 11.3, 12.3, 13.5, 14.4,
14.5, 15.3, 16.2, CCP5.2, CCP6.2}