Editing IPCC:AR6/WGII/Chapter-18 (section)

==== 18.5.1.1 Climate Change Risk for Different Global Regions ====

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Two important elements of understanding the opportunities and challenges associated with the pursuit of CRD in different regional contexts are a) the geographic variability in climate conditions that shape livelihoods, behaviours and responses of human and natural systems; and b) how those conditions could shift in the future in response to climate change, which determines the additional burden that climate change could create for adaptation and sustainable development.

The climate analyses of WGI provide information on regional differences in temperature, rainfall and sea surface temperatures for different global regions and how they are projected to change in response to different levels of aggregate global warming (Table 18.4). Such data reveal that even when aggregated to broad geographic regions, significant variations exist for all of these parameters, which is a function of the baseline climatology of each region. For example, temperatures in Africa and Australia are, on average, warmer than in Europe or North America. Significant variations are also observed for rainfall variables. Such regional variation in climate conditions is part of the regional context that shapes current patterns of development of the past present and future. They influence biodiversity and natural resource availability as well as exposure to climatic extremes (tropical storms, heatwaves and drought) that contribute to disasters.

The WGI data also indicate that increases in globally averaged temperatures will have different consequences for regional climate change (Table 18.4), including variation in the magnitude and, for precipitation, even the direction of change ( ''very high confidence'' ). For example, although average temperatures, daily minimum temperature and the number of days over a given threshold are projected to increase in all regions except Antarctica, the magnitude of the change varies. Moreover, little change is projected for daily maximum temperatures across different regions. Nevertheless, the number of days over different temperature thresholds such as 35°C increases markedly in most regions, reflecting the disproportionate impact that global warming has on the tails of temperature distributions. Given outcomes in many systems including public health, agriculture, ecosystems and biodiversity, and infrastructure are often associated with biophysical thresholds (e.g., physiological or design thresholds), those regions where such thresholds are increasingly exceeded due to climate change may experience disproportionately higher impacts ( ''very high confidence'' ). Given such temperatures occur more frequently in regions such as Africa and Central and South America, this disproportionate exposure is exacerbated by disproportionate vulnerability, adaptation gaps and development needs ( ''very high confidence'' ; [[#18.2.4|Section 18.2.4]] ; Table 18.4).

The regional response of precipitation to globally averaged temperature increases is less clear than temperature, in part due to high intra-region variability. Average daily precipitation remains fairly stable in all global regions in response to higher magnitudes of global warming (Table 18.4). However, 5-day precipitation totals provide a clearer signal of increasing hydrologic activity in response to higher globally averaged temperatures (Table 18.4). Such data does not necessarily reflect changes in rainfall extremes that could occur with downstream consequences for hazards such as drought or flooding. Similarly, while sea surface temperatures (SSTs) are more uniform across global ocean basins, all basins are anticipated to warm in response to higher globally averaged temperatures (Table 18.5). Unlike temperature, however, SST increases are anticipated to be only a fraction of the globally averaged increase in temperature, due in large part to the heat capacity of the oceans. Nevertheless, such higher SSTs have implications not only for ocean ecosystems and the distribution of marine species, but also for weather patterns, such as formation and intensity of tropical cyclones ( ''very high confidence'' ).

The other aspect of the regional climate responses to global temperature increases that is important for CRD is the marked differences observed between changes in response to 1.5°C versus 4°C of warming. Higher levels of global warming are associated with higher regional changes, including changes in extremes of temperature. This in turn increases climate risk to exposed and vulnerable human and natural systems, thereby increasing demand for adaptation. If that demand is not met, then the adaptation gap will be larger, with greater risk of loss and damage ( ''very high confidence'' ) ( [[#Schaeffer--2015|Schaeffer et al., 2015]] ; [[#Chen--2016|Chen et al., 2016]] ; United Nations Environment Programme, 2021). This is true not only for regions, but also at the sectoral level ( [[#18.5.2|Section 18.5.2]] ). Therefore, CRD pathways must balance the demands for emissions reductions to reduce exposure, adaptation to manage residual climate change risks, and sustainable development to address vulnerability and enhance capacity for sustainable development.

'''Table 18.5 |''' Projected sea surface temperature change ranges by global warming level and ocean biome (°C). Ranges are 5th and 95th percentiles from SSP5-8.5 WGI CMIP6 ensemble results. There is little variation in the 5th and 95th percentile values by GWL across the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 projections. Source: WGI AR6 Interactive Atlas (Gutiérrez et al., 2021).

{| class="wikitable"
|-
! '''Global warming level'''

! '''All ocean biomes'''

! '''Northern Hemisphere; high latitudes'''

! '''Northern Hemisphere; Subtropics'''

! '''Equatorial'''

! '''Southern Hemisphere; Subtropics'''

! '''Southern Hemisphere; high latitudes'''

! '''Gulf of Mexico'''

! '''Eastern Boundaries'''

! '''Amazon River'''

! '''Arabian Sea'''

! '''Indonesian flowthrough'''

|-
| '''4°C'''

| 1.9 to 2.4

| 2.0 to 3.3

| 2.2 to 2.8

| 2.1 to 3.0

| 1.8 to 2.4

| 1.3 to 2.0

| 2.1 to 2.8

| 2.1 to 2.7

| 1.7 to 2.5

| 2.3 to 2.9

| 1.9 to 2.7

|-
| '''3°C'''

| 1.3 to 1.7

| 1.2 to 2.2

| 1.4 to 2.4

| 1.4 to 2.2

| 1.2 to 1.7

| 0.7 to 1.4

| 1.5 to 2.3

| 1.4 to 2.1

| 1.2 to 2.0

| 1.6 to 2.2

| 1.3 to 1.9

|-
| '''2°C'''

| 0.6 to 1.0

| 0.5 to 1.4

| 0.7 to 1.4

| 0.7 to 1.3

| 0.5 to 1

| 0.3 to 0.8

| 0.6 to 1.4

| 0.6 to 1.3

| 0.6 to 1.3

| 0.6 to 1.3

| 0.5 to 1.2

|-
| '''1.5°C'''

| 0.2 to 0.7

| 0.1 to 0.9

| 0.2 to 1.0

| 0.2 to 0.8

| 0.2 to 0.6

| 0.1 to 0.5

| 0.2 to 1.0

| 0.2 to 0.9

| 0.2 to 0.9

| 0.2 to 0.9

| 0.1 to 0.8

|}

'''Table 18.4 |''' Projected continental level result ranges for select temperature and precipitation climate change variables by global warming level. Ranges are 5th and 95th percentiles from SSP5-8.5 WGI CMIP6 ensemble results. There is little variation in the 5th and 95th percentile values by GWL across the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 projections. Source: WGI AR6 Interactive Atlas (Gutiérrez et al., 2021).

{| class="wikitable"
|-
! '''Climate variable'''

! '''Global warming level'''

! '''All Regions'''

! '''North America'''

! '''Europe'''

! '''Asia'''

! '''Central–South America'''

! '''Africa'''

! '''Australia'''

! '''Antarctica'''

|-
| rowspan="4"| '''Mean temperature (°C)'''

| '''4°C'''

| 12 to 15

| 8 to 11

| 5 to 9

| 12 to 14

| 24 to 27

| 26 to 29

| 24 to 27

| −33 to −27

|-
| '''3°C'''

| 11 to 14

| 6 to 11

| 4 to 7

| 10 to 14

| 23 to 26

| 25 to 28

| 23 to 26

| −35 to −26

|-
| '''2°C'''

| 10 to 13

| 5 to 9

| 3 to 6

| 8 to 12

| 22 to 25

| 24 to 27

| 22 to 25

| −36 to −27

|-
| '''1.5°C'''

| 9 to 12

| 4 to 8

| 2 to 5

| 8 to 12

| 22 to 24

| 24 to 26

| 22 to 24

| −36 to −27

|-
| rowspan="4"| '''Minimum of daily minimum temperatures (°C)'''

| '''4°C'''

| −12 to −5

| −25 to −15

| −22 to −14

| −18 to −9

| 11 to 15

| 10 to 14

| 5 to 10

| −64 to −48

|-
| '''3°C'''

| −13 to −6

| −27 to −15

| −24 to −15

| −20 to −11

| 10 to 15

| 8 to 14

| 4 to 10

| −64 to −50

|-
| '''2°C'''

| −15 to −8

| −30 to −18

| −27 to −17

| −22 to −13

| 9 to 14

| 7 to 13

| 3 to 9

| −65 to −51

|-
| '''1.5°C'''

| −16 to −9

| −32 to −20

| −28 to −19

| −23 to −14

| 8 to 14

| 6 to 12

| 3 to 9

| −66 to −51

|-
| rowspan="4"| '''Maximum of daily maximum temperatures (°C)'''

| '''4°C'''

| 32 to 37

| 32 to 38

| 28 to 33

| 35 to 40

| 36 to 43

| 40 to 47

| 41 to 49

| −12 to −5

|-
| '''3°C'''

| 31 to 39

| 31 to 38

| 28 to 34

| 35 to 41

| 35 to 44

| 39 to 51

| 41 to 54

| −12 to −3

|-
| '''2°C'''

| 30 to 37

| 30 to 36

| 26 to 33

| 33 to 39

| 34 to 43

| 38 to 50

| 39 to 53

| −13 to −4

|-
| '''1.5°C'''

| 29 to 36

| 29 to 35

| 25 to 31

| 32 to 39

| 33 to 42

| 38 to 49

| 39 to 52

| −14 to −5

|-
| rowspan="4"| '''Number of days with maximum temperature above 35°C—bias adjusted'''

| '''4°C'''

| 81 to 106

| 36 to 50

| 11 to 22

| 57 to 77

| 138 to 194

| 153 to 210

| 140 to 168

| 0 to 0

|-
| '''3°C'''

| 66 to 87

| 27 to 40

| 6 to 15

| 44 to 59

| 100 to 153

| 131 to 183

| 124 to 147

| 0 to 0

|-
| '''2°C'''

| 52 to 68

| 19 to 29

| 4 to 8

| 33 to 45

| 61 to 106

| 116 to 151

| 102 to 124

| 0 to 0

|-
| '''1.5°C'''

| 45 to 58

| 16 to 24

| 2 to 5

| 30 to 39

| 43 to 85

| 107 to 133

| 94 to 115

| 0 to 0

|-
| rowspan="4"| '''Near-surface total precipitation (mm/d)'''

| '''4°C'''

| 2 to 3

| 2 to 3

| 2 to 2

| 2 to 3

| 4 to 5

| 2 to 3

| 1 to 2

| 1 to 1

|-
| '''3°C'''

| 2 to 3

| 2 to 3

| 2 to 2

| 2 to 3

| 3 to 5

| 2 to 3

| 1 to 2

| 1 to 1

|-
| '''2°C'''

| 2 to 3

| 2 to 3

| 2 to 2

| 2 to 3

| 3 to 5

| 2 to 3

| 1 to 2

| 1 to 1

|-
| '''1.5°C'''

| 2 to 3

| 2 to 3

| 2 to 2

| 2 to 3

| 3 to 5

| 2 to 3

| 1 to 2

| 1 to 1

|-
| rowspan="4"| '''Maximum 5-day precipitation amount (mm)'''

| '''4°C'''

| 79 to 99

| 75 to 93

| 53 to 71

| 81 to 105

| 118 to 168

| 68 to 113

| 81 to 124

| 20 to 29

|-
| '''3°C'''

| 66 to 99

| 68 to 87

| 48 to 68

| 70 to 101

| 97 to 165

| 60 to 118

| 76 to 129

| 19 to 27

|-
| '''2°C'''

| 64 to 93

| 65 to 84

| 47 to 65

| 66 to 95

| 93 to 162

| 55 to 107

| 73 to 122

| 18 to 26

|-
| '''1.5°C'''

| 63 to 91

| 63 to 83

| 46 to 64

| 64 to 93

| 92 to 160

| 52 to 105

| 74 to 119

| 18 to 25

|}

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