Editing IPCC:AR6/SR15/Chapter-3 (section)

== 3.4.11 Interacting and Cascading Risks ==

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The literature on compound as well as interacting and cascading risks at warming of 1.5°C and 2°C is limited. Spatially compound risks, often referred to as hotspots, involve multiple hazards from different sectors overlapping in location (Piontek et al., 2014) <sup>[[#fn:r1101|1101]]</sup> . Global exposures were assessed for 14 impact indicators, covering water, energy and land sectors, from changes including drought intensity and water stress index, cooling demand change and heatwave exposure, habitat degradation, and crop yields using an ensemble of climate and impact models (Byers et al., 2018) <sup>[[#fn:r1102|1102]]</sup> . Exposures are projected to approximately double between 1.5°C and 2°C, and the land area affected by climate risks is expected to increase as warming progresses. For populations vulnerable to poverty, the exposure to climate risks in multiple sectors could be an order of magnitude greater (8–32 fold) in the high poverty and inequality scenarios (SSP3; 765–1,220 million) compared to under sustainable socio-economic development (SSP1; 23–85 million). Asian and African regions are projected to experience 85–95% of global exposure, with 91–98% of the exposed and vulnerable population (depending on SSP/GMT combination), approximately half of which are in South Asia. Figure 3.19 shows that moderate and large multi-sector impacts are prevalent at 1.5°C where vulnerable people live, predominantly in South Asia (mostly Pakistan, India and China), but that impacts spread to sub-Saharan Africa, the Middle East and East Asia at higher levels of warming. Beyond 2°C and at higher risk thresholds, the world’s poorest populations are expected to be disproportionately impacted, particularly in cases (SSP3) of great inequality in Africa and southern Asia. Table 3.4 shows the number of exposed and vulnerable people at 1.5°C and 2°C of warming, with 3°C shown for context, for selected multi-sector risks.

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====== Figure 3.19 ======

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==== Multi-sector risk maps for 1.5°C (top), 2°C (middle), and locations where 2°C brings impacts not experienced at 1.5°C (2°C–1.5°C; bottom). ====

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The maps in the left column show the full range of the multi-sector risk (MSR) score (0–9), with scores ≤5.0 shown with a transparency gradient and scores &gt;5.0 shown with a colour gradient. Score must be &gt;4.0 to be considered ‘multi-sector’. The maps in the right column overlay the 2050 vulnerable populations (low income) under Shared Socio-Economic Pathway (SSP)2 (greyscale) with the multi-sector risk score &gt;5.0 (colour gradient), thus indicating the concentrations of exposed and vulnerable populations to risks in multiple sectors. Source: Byers et al. (2018) <sup>[[#fn:r1103|1103]]</sup> .

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====== Table 3.4 ======

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==== Number of exposed and vulnerable people at 1.5°C, 2°C, and 3°C for selected multi-sector risks under shared socioeconomic pathways (SSPs).  ====

Source: Byers et al. (2018) <sup>[[#fn:r1104|1104]]</sup>

{| class="wikitable"
|-
! SSP2<br />
(SSP1 to SSP3 range), millions
! colspan="2"| 1.5°C
! colspan="2"| 2°C
! colspan="2"| 3°C
|-
| ''Indicator''
| Exposed
| Exposed<br />
and vulnerable
| Exposed
| Exposed<br />
and vulnerable
| Exposed
| Exposed<br />
and vulnerable
|-
| Water stress index
| 3340
(3032–3584)

| 496
(103–1159)

| 3658
(3080–3969)

| 586
(115–1347)

| 3920
(3202–4271)

| 662
(146–1480)

|-
| Heatwave event exposure
| 3960
(3546–4508)

| 1187
(410–2372)

| 5986
(5417–6710)

| 1581
(506–3218)

| 7909
(7286–8640)

| 1707
(537–3575)

|-
| Hydroclimate risk to power production
| 334
(326–337)

| 30
(6–76)

| 385
(374–389)

| 38
(9–94)

| 742
(725–739)

| 72
(16–177)

|-
| Crop yield change
| 35
(32–36)

| 8
(2–20)

| 362
(330–396)

| 81
(24–178)

| 1817
(1666–1992)

| 406
(118–854)

|-
| Habitat degradation
| 91
(92–112)

| 10
(4–31)

| 680
(314–706)

| 102
(23–234)

| 1357
(809–1501)

| 248
(75–572)

|-
| Multi-sector exposure
|
|-
| Two indicators
| 1129
(1019–1250)

| 203
(42–487)

| 2726
(2132–2945)

| 562
(117–1220)

| 3500
(3212–3864)

| 707
(212–1545)

|-
| Three indicators
| 66
(66–68)

| 7
(0.9–19)

| 422
(297–447)

| 54
(8–138)

| 1472
(1177–1574)

| 237
(48–538)

|-
| Four indicators
| 5
(0.3–5.7)

| 0.3
(0–1.2)

| 11
(5–14)

| 0.5
(0–2)

| 258
(104–280)

| 33
(4–86)

|}

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