Editing IPCC:AR6/WGII/Chapter-9 (section)

==== 9.9.4.1 Projected Risks for Human Settlements ====

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The extent of urban areas in Africa exposed to climate hazards will increase considerably and cities will be hotspots of climate risks, which could amplify pre-existing stresses related to poverty, exclusion and governance ( ''high confidence'' ) ( [[#IPCC--2018b|IPCC, 2018b]] ).

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<span id="flooding"></span>
===== 9.9.4.1.1 Flooding =====

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Continuing current population and GDP growth trends, the extent of urban land exposed to high-frequency flooding is projected to increase around 270% in north Africa, 800% in southern Africa, and 2600% in mid-latitude Africa by 2030 when compared to 2000, without considering climate change ( [[#Güneralp--2015|Güneralp et al., 2015]] ). In addition, global warming is projected to increase frequency and magnitude of river floods in east, central and west Africa ( [[#Alfieri--2017|Alfieri et al., 2017]] ; [[#Gu--2020|Gu et al., 2020]] ; [[#Kam--2021|Kam et al., 2021]] ). On average, across large African river basins, the frequency of flood events with a current return period of 100 years is projected to increase to 1 in 40 years at 1.5°C and 2°C global warming, and 1 in 21 years at 4°C warming, with Egypt, Nigeria, Sudan and the Democratic Republic of Congo in the top 20 countries globally for projected damages ( [[#Alfieri--2017|Alfieri et al., 2017]] ). Compared to population in 2000, human displacement due to river flooding in sub-Saharan Africa is projected to increase 600% by 2066–2096 with moderate-to-high population growth and 2.6°C global warming, with risk reducing to a 200% increase for low population growth and 1.6°C global warming ( [[#Kam--2021|Kam et al., 2021]] ).

Urban population exposure to tropical cyclone hazards in southeastern Africa, in particular Mozambique, is projected to increase due to the intensification of cyclones and their extended duration associated with warmer sea surface temperatures ( [[#Fitchett--2018|Fitchett, 2018]] ; [[#Vidya--2020|Vidya et al., 2020]] ). Urban damage assessment based on a 10-year flood protection level for Accra, Ghana, shows that without flood protection, there is a 10% probability of a flood occurring annually which could cause USD 98.5 million urban damage, affect GDP by USD 50.3 million and affect 34,000 people ( [[#Asumadu-Sarkodie--2015|Asumadu-Sarkodie et al., 2015]] ). Many urban households and Africa’s growing assets could therefore be exposed to increased flooding ( [[#IPCC--2018b|IPCC, 2018b]] ).

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<span id="sea-level-rise-and-coastal-flooding"></span>
===== 9.9.4.1.2 Sea level rise and coastal flooding =====

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Africa’s low-lying coastal zone population is expected to grow more than any other region from 2000 to 2060 (see Figure 9.28; [[#Neumann--2015|Neumann et al., 2015]] ). Future rapid coastal development is expected to increase existing high vulnerabilities to sea level rise (SLR) and coastal hazards, particularly in east Africa ( ''high confidence'' ) (Figure 9.29; [[#Hinkel--2012|Hinkel et al., 2012]] ; [[#Kulp--2019|Kulp and Strauss, 2019]] ). By 2100, sea levels are projected to rise at least 40 cm above those in 2000 in a below 2°C scenario, and possibly up to 1 m by the end of the century under a 4°C warming scenario ( [[#Serdeczny--2017|Serdeczny et al., 2017]] ; see also Cross-Chapter Box SLR in Chapter 3).

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[[File:112cbee81c32c023e3fdb2f8c1e6b9b0 IPCC_AR6_WGII_Figure_9_028.png]]

'''Figure 9.28 |''' '''Tens to hundreds of millions of people in Africa are projected to be exposed to sea level rise, with a major risk driver being increased exposure due to population increase in low-lying areas.'''

'''(a)''' Population in the low-elevation coastal zone (LECZ) projected to be exposed to mean sea level rise (SLR) for 2030 (+10 cm SLR) and 2060 (+21 cm SLR). Scenarios A, C have exclusive social, political and economic governance whereas scenarios B and D have inclusive social, political and economic governance.

'''(b)''' African countries with the highest projected population numbers in the LECZ, and also the additional population projected to be exposed in these countries due to a 1-in-100 year storm surge event. For panel b projections of population exposure used the high population growth socio-economic scenario (scenario C). Data sourced from [[#Neumann--2015|Neumann et al. (2015)]] .

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[[File:5a391848b4f227f3ceb881fd706a9c8d IPCC_AR6_WGII_Figure_9_029.png]]

'''Figure 9.29 |''' '''Multiple large African cities will be exposed to sea level rise (SLR), these include the selected examples:''' '''(a)''' Dar es Salaam, Bagamoyo, and Stone Town in Tanzania (east Africa), '''(b)''' Lagos in Nigeria, and Cotonou and Porto-Novo in Benin (west Africa) and '''(c)''' Cairo and Alexandria in Egypt (north Africa). Orange shows built-up area in 2014. Shades of blue show permanent flooding due to SLR by 2050 and 2100 under low (RCP2.6), intermediate (RCP4.5) and high (RCP8.5) greenhouse gas emissions scenarios. Darker colours for higher emissions scenarios show areas projected to be flooded in addition to those for lower emissions scenarios. The figure assumes failure of coastal defences in 2050 and 2100. Some areas are already below current SLR and coastal defences need to be upgraded as SLRs (e.g., in Egypt), others are just above mean sea levels and they do not necessarily have high protection levels, so these defences need to be built (e.g., Dar es Salaam and Lagos). Blue shading shows permanent inundation surfaces predicted by Coastal Digital Elevation Model (DEM) and Shuttle Radar Topography Mission (SRTM) given the 95th percentile K14/RCP2.6, RCP4.5 and RCP8.5, for present day, 2050, and 2100 sea level projection for permanent inundation (inundation without a storm surge event), and RL10 (10-year return level storm) ( [[#Kulp--2019|Kulp and Strauss, 2019]] ). Low-lying areas isolated from the ocean are removed from the inundation surface using connected components analysis. Current water bodies are derived from the SRTM Water Body Dataset. Orange areas represent the extent of coastal human settlements in 2014 ( [[#Corbane--2018|Corbane et al., 2018]] ). See Figure CCP4.7 for projections including subsidence and worst-case scenario projections for 2100.

In the absence of any adaptation, Egypt, Mozambique, and Nigeria are projected to be worst affected by SLR in terms of the number of people at risk of flooding annually in a 4°C warming scenario ( [[#Hinkel--2012|Hinkel et al., 2012]] ). Recent estimates have explored the potential damages due to SLR and coastal extreme events in 12 major African cities using a stochastic approach to account for uncertainty ( [[#Abadie--2020|Abadie et al., 2020]] ). The aggreate of expected average damages to these cities in 2050 is USD 65 billion for RCP4.5 and USD 86.5 billion for RCP8.5, and USD 137.5 billion under a high-end scenario that incorporates expert opinion on additional ice sheet melting with damages up to (Table 9.8). When considering low-probability, high-damage events, aggregate damage risks can be more than twice as high, reaching USD 187 billion and USD 206 billion under RCP4.5 and RCP8.5 scenarios, respectively, and USD 397 billion under the high-end scenario. City characteristics and exposure play a larger role in expected damages and risk than changes in sea level. The city of Alexandria in north Africa leads the ranking, with aggregate expected damage of USD 36 billion and USD 50 billion under RCP4.5 and RCP8.5 scenarios, respectively, and USD 79.4 billion under a high-end scenario.

Sea level rise and associated episodic flooding are identified as key drivers of projected net migration of 750,000 people out of the east African coastal zone between 2020 and 2050 ( [[#IPCC--2019a|IPCC, 2019a]] ). These trends, alongside the emergence of ‘hotspots’ of climate in- and out-migration (Box 9.8), will have major implications for climate-sensitive sectors and the adequacy of human settlements, including urban infrastructure and social support systems. Actions which could help reduce the number of people being forced to move in distress, include adoption of inclusive and CRD policies, together with targeted investments to manage the reality of climate migration; and mainstreaming climate migration in development planning (Box 9.8).

'''Table 9.8 |''' Regional relative sea level rise (SLR) for 2050 and 2100, and associated aggregated expected damage risks over the period 2020 to 2050 in 12 major African coastal cities under four SLR scenarios. '''(a)''' Regional relative SLR by 2050 and 2100. For SLR, median and 95th percentiles are presented, in centimetres. '''(b)''' Probabilistic damage estimations by 2050 include expected average damages (EAD), damages at the 95th percentile (value at risk; VaR) and the expected shortfall (ES), which represents the average damages of the 5% worst cases. Four relative sea level projections were considered under no adaptation: the RCP2.6, 4.5 and 8.5 scenarios from the ( [[#IPCC--2014a|IPCC, 2014a]] ), and a high-end RCP8.5 scenario that incorporates expert opinion on additional ice sheet melting. Note that figures are provided in undiscounted millions of US dollars (2005) and have been rounded off to avoid a false sense of precision ( [[#Abadie--2020|Abadie et al., 2020]] ; [[#Abadie--2021|Abadie et al., 2021]] ).

{| class="wikitable"
|-
! colspan="13"| (a) Regional relative sea level rise (cm)

|-
! rowspan="2"| City

! rowspan="2"| Year

! colspan="3"| RCP2.6

! colspan="3"| RCP4.5

! colspan="3"| RCP8.5

! colspan="2"| High-end

|-
! colspan="2"| Median

! P95

! colspan="2"| Median

! P95

! colspan="2"| Median

! P95

! Median

! P95

|-
| rowspan="2"| '''Abidjan'''

| '''2050'''

| colspan="2"| '''21'''

| '''30'''

| colspan="2"| '''22'''

| '''32'''

| colspan="2"| '''24'''

| '''34'''

| '''28'''

| '''48'''

|-
| '''2100'''

| colspan="2"| '''44'''

| '''69'''

| colspan="2"| '''53'''

| '''86'''

| colspan="2"| '''75'''

| '''114'''

| '''86'''

| '''206'''

|-
| rowspan="2"| '''Alexandria'''

| '''2050'''

| colspan="2"| '''18'''

| '''26'''

| colspan="2"| '''18'''

| '''28'''

| colspan="2"| '''21'''

| '''30'''

| '''25'''

| '''43'''

|-
| '''2100'''

| colspan="2"| '''36'''

| '''58'''

| colspan="2"| '''46'''

| '''73'''

| colspan="2"| '''67'''

| '''102'''

| '''78'''

| '''186'''

|-
| rowspan="2"| '''Algiers'''

| '''2050'''

| colspan="2"| '''19'''

| '''27'''

| colspan="2"| '''19'''

| '''29'''

| colspan="2"| '''22'''

| '''31'''

| '''25'''

| '''45'''

|-
| '''2100'''

| colspan="2"| '''39'''

| '''62'''

| colspan="2"| '''47'''

| '''76'''

| colspan="2"| '''66'''

| '''98'''

| '''78'''

| '''192'''

|-
| rowspan="2"| '''Cape Town'''

| '''2050'''

| colspan="2"| '''20'''

| '''30'''

| colspan="2"| '''21'''

| '''31'''

| colspan="2"| '''23'''

| '''33'''

| '''27'''

| '''48'''

|-
| '''2100'''

| colspan="2"| '''44'''

| '''69'''

| colspan="2"| '''53'''

| '''87'''

| colspan="2"| '''75'''

| '''117'''

| '''86'''

| '''199'''

|-
| rowspan="2"| '''Casablanca'''

| '''2050'''

| colspan="2"| '''19'''

| '''27'''

| colspan="2"| '''20'''

| '''29'''

| colspan="2"| '''22'''

| '''31'''

| '''26'''

| '''46'''

|-
| '''2100'''

| colspan="2"| '''39'''

| '''63'''

| colspan="2"| '''47'''

| '''78'''

| colspan="2"| '''65'''

| '''99'''

| '''77'''

| '''198'''

|-
| rowspan="2"| '''Dakar'''

| '''2050'''

| colspan="2"| '''21'''

| '''31'''

| colspan="2"| '''21'''

| '''31'''

| colspan="2"| '''23'''

| '''33'''

| '''27'''

| '''48'''

|-
| '''2100'''

| colspan="2"| '''43'''

| '''69'''

| colspan="2"| '''53'''

| '''86'''

| colspan="2"| '''73'''

| '''111'''

| '''85'''

| '''209'''

|-
| rowspan="2"| '''Dar es Salaam'''

| '''2050'''

| colspan="2"| '''20'''

| '''29'''

| colspan="2"| '''21'''

| '''31'''

| colspan="2"| '''24'''

| '''33'''

| '''27'''

| '''47'''

|-
| '''2100'''

| colspan="2"| '''45'''

| '''70'''

| colspan="2"| '''54'''

| '''86'''

| colspan="2"| '''76'''

| '''117'''

| '''87'''

| '''206'''

|-
| rowspan="2"| '''Durban'''

| '''2050'''

| colspan="2"| '''20'''

| '''30'''

| colspan="2"| '''22'''

| '''32'''

| colspan="2"| '''25'''

| '''34'''

| '''28'''

| '''49'''

|-
| '''2100'''

| colspan="2"| '''46'''

| '''72'''

| colspan="2"| '''55'''

| '''90'''

| colspan="2"| '''78'''

| '''119'''

| '''89'''

| '''207'''

|-
| rowspan="2"| '''Lagos'''

| '''2050'''

| colspan="2"| '''21'''

| '''30'''

| colspan="2"| '''22'''

| '''32'''

| colspan="2"| '''24'''

| '''34'''

| '''28'''

| '''48'''

|-
| '''2100'''

| colspan="2"| '''44'''

| '''69'''

| colspan="2"| '''54'''

| '''86'''

| colspan="2"| '''75'''

| '''113'''

| '''86'''

| '''205'''

|-
| rowspan="2"| '''Lome'''

| '''2050'''

| colspan="2"| '''21'''

| '''30'''

| colspan="2"| '''22'''

| '''32'''

| colspan="2"| '''24'''

| '''34'''

| '''28'''

| '''48'''

|-
| '''2100'''

| colspan="2"| '''44'''

| '''69'''

| colspan="2"| '''53'''

| '''86'''

| colspan="2"| '''76'''

| '''115'''

| '''87'''

| '''205'''

|-
| rowspan="2"| '''Luanda'''

| '''2050'''

| colspan="2"| '''21'''

| '''30'''

| colspan="2"| '''23'''

| '''32'''

| colspan="2"| '''25'''

| '''35'''

| '''29'''

| '''49'''

|-
| '''2100'''

| colspan="2"| '''45'''

| '''70'''

| colspan="2"| '''55'''

| '''88'''

| colspan="2"| '''78'''

| '''119'''

| '''90'''

| '''205'''

|-
| rowspan="2"| '''Maputo'''

| '''2050'''

| colspan="2"| '''21'''

| '''31'''

| colspan="2"| '''22'''

| '''32'''

| colspan="2"| '''24'''

| '''34'''

| '''28'''

| '''49'''

|-
| '''2100'''

| colspan="2"| '''45'''

| '''71'''

| colspan="2"| '''55'''

| '''89'''

| colspan="2"| '''78'''

| '''120'''

| '''89'''

| '''209'''

|-
| colspan="13"| '''(b) Expected average damages and risk measures (USD millions)'''

|-
| rowspan="2"| '''City'''

| colspan="3"| '''RCP2.6'''

| colspan="3"| '''RCP4.5'''

| colspan="3"| '''RCP8.5'''

| colspan="3"| '''High-end scenario'''

|-
| '''EAD'''

| '''VaR(95%)'''

| '''ES(95%)'''

| '''EAD'''

| '''VaR(95%)'''

| '''ES(95%)'''

| '''EAD'''

| '''VaR(95%)'''

| '''ES(95%)'''

| '''EAD'''

| '''VaR(95%)'''

| '''ES(95%)'''

|-
| '''Abidjan'''

| '''14,290'''

| '''33,910'''

| '''41,690'''

| '''16,730'''

| '''38,230'''

| '''46,390'''

| '''20,910'''

| '''42,140'''

| '''49,550'''

| '''32,670'''

| '''77,750'''

| '''96,570'''

|-
| '''Alexandria'''

| '''32,840'''

| '''74,100'''

| '''92,470'''

| '''36,220'''

| '''83,700'''

| '''104,270'''

| '''49,990'''

| '''99,500'''

| '''117,580'''

| '''79,360'''

| '''180,090'''

| '''221,390'''

|-
| '''Algiers'''

| '''270'''

| '''620'''

| '''760'''

| '''300'''

| '''700'''

| '''870'''

| '''390'''

| '''810'''

| '''960'''

| '''640'''

| '''1,540'''

| '''1,920'''

|-
| '''Cape Town'''

| '''110'''

| '''310'''

| '''400'''

| '''130'''

| '''360'''

| '''450'''

| '''170'''

| '''410'''

| '''490'''

| '''300'''

| '''800'''

| '''1,010'''

|-
| '''Casablanca'''

| '''350'''

| '''1,150'''

| '''1,520'''

| '''420'''

| '''1,340'''

| '''1,740'''

| '''610'''

| '''1,570'''

| '''1,930'''

| '''1,230'''

| '''3,590'''

| '''4,630'''

|-
| '''Dakar'''

| '''590'''

| '''1,310'''

| '''1,590'''

| '''620'''

| '''1,390'''

| '''1,690'''

| '''760'''

| '''1,530'''

| '''1,800'''

| '''1,180'''

| '''2,880'''

| '''3,610'''

|-
| '''Dar es Salaam'''

| '''880'''

| '''2,100'''

| '''2,600'''

| '''1,050'''

| '''2,440'''

| '''2,970'''

| '''1,360'''

| '''2,760'''

| '''3,250'''

| '''2,140'''

| '''5,120'''

| '''6,360'''

|-
| '''Durban'''

| '''110'''

| '''370'''

| '''470'''

| '''150'''

| '''420'''

| '''530'''

| '''210'''

| '''490'''

| '''590'''

| '''370'''

| '''970'''

| '''1,230'''

|-
| '''Lagos'''

| '''3,680'''

| '''6,790'''

| '''7,950'''

| '''4,200'''

| '''7,660'''

| '''8,930'''

| '''4,920'''

| '''8,270'''

| '''9,420'''

| '''6,750'''

| '''13,820'''

| '''16,730'''

|-
| '''Lome'''

| '''3,230'''

| '''10,480'''

| '''13,460'''

| '''4,280'''

| '''12,580'''

| '''15,780'''

| '''5,980'''

| '''14,430'''

| '''17,380'''

| '''10,720'''

| '''28,580'''

| '''36,010'''

|-
| '''Luanda'''

| '''160'''

| '''380'''

| '''470'''

| '''200'''

| '''440'''

| '''530'''

| '''260'''

| '''510'''

| '''600'''

| '''400'''

| '''910'''

| '''1,130'''

|-
| '''Maputo'''

| '''650'''

| '''1,990'''

| '''2,530'''

| '''700'''

| '''2,080'''

| '''2,620'''

| '''980'''

| '''2,410'''

| '''2,910'''

| '''1,790'''

| '''4,830'''

| '''6,110'''

|-
| '''Aggregate damage'''

'''and risk'''

| '''57,160'''

| '''133,510'''

| '''165,910'''

| '''65,000'''

| '''151,340'''

| '''186,770'''

| '''86,540'''

| '''174,830'''

| '''206,460'''

| '''137,550'''

| '''320,880'''

| '''396,700'''

|}

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<span id="drought"></span>
===== 9.9.4.1.3 Drought =====

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Although an increase in drought hazard is projected for north and southwest southern Africa with increased global warming (Figure 9.15), central African countries may have the highest drought risk because of high vulnerability and high population growth ( [[#Ahmadalipour--2019|Ahmadalipour et al., 2019]] ). Among continents, Africa contains the second largest population of people living in drylands, which is expected to double by 2050 ( [[#IPCC--2019a|IPCC, 2019a]] ). Continuing current population and GDP growth trends, the extent of urban land in arid zones is projected to increase around 180% in southern Africa, 300% in north Africa and 700% in mid-latitude Africa by 2030 when compared to 2000, without considering climate change ( [[#Güneralp--2015|Güneralp et al., 2015]] ). At 1.5°C warming, urban populations exposed to severe droughts in west Africa are projected to increase (65±34 million) and increase further at 2°C ( [[#IPCC--2018b|IPCC, 2018b]] ; [[#Liu--2018b|Liu et al., 2018b]] ). Risks associated with increases in drought frequency and magnitudes are projected to be substantially larger at 2°C than at 1.5°C for north Africa and southern Africa ( [[#IPCC--2018b|IPCC, 2018b]] ; [[#Oppenheimer--2019|Oppenheimer et al., 2019]] ). Dryland populations exposed (vulnerable) to water stress, heat stress, and desertification are projected to reach 951 (178) million at 1.5°C, 1152 (220) million at 2°C, and 1285 (277) million at 3°C of global warming ( [[#IPCC--2019a|IPCC, 2019a]] ). At global warming of 2°C under a scenario of low population growth and sustainable development (SSP1), the exposed (vulnerable) dryland population is 974 (35) million and for higher population growth and low environmental protections (SSP3) it is 1.27 billion (522 million), a majority of which is in west Africa ( [[#IPCC--2019a|IPCC, 2019a]] ).

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<span id="extreme-heat"></span>
===== 9.9.4.1.4 Extreme heat =====

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Projections for 173 African cities show that around 25 cities will have over 150 days per year with an apparent temperature above 40.6°C for 1.7°C global warming, increasing to 35 cities for 2.1°C and 65 cities for 4.4°C warming, with west African cities most affected ( [[#Rohat--2019|Rohat et al., 2019]] ). Across Africa, urban population exposure to extreme heat was estimated to be 2 billion person-days per year above 40°C for 1985–2005 (that is the annual average number of days with a maximum temperature above 40.6°C multiplied by the number of people exposed to that temperature), but this is expected to increase to 45 billion person-days for 1.7°C global warming with low population growth (SSP1), and to 95 billion person-days for 2.8°C and medium-high population growth (SSP4) by the 2060s, with increases of 20–52 times 1985–2005 levels by 2080–2100, depending on the scenario ( [[#Rohat--2019|Rohat et al., 2019]] ). West Africa (especially Nigeria) has the highest absolute exposure and southern Africa the least. Considering the urban heat island effect, the more vulnerable populations under 5 and over 64 exposed to heat waves of &gt;15 days over 42°C are projected to increase from 27 million in 2010 to 360 million by 2100 for low population growth (SSP1) with 1.8°C global warming, increasing to 440 million for low population growth (SSP5) with &gt;4°C global warming, with west Africa most affected ( [[#Marcotullio--2021|Marcotullio et al., 2021]] ). This portends increased vulnerability to risk of heat stress in big cities of central, east and west Africa ( ''very high confidence'' ) ( [[#Gasparrini--2015|Gasparrini et al., 2015]] ; [[#Liu--2017|Liu et al., 2017]] ; [[#Rohat--2019|Rohat et al., 2019]] ). Shifting to a low urban population growth pathway is projected to achieve a greater reduction in aggregate exposure to extreme heat for most cities in west Africa, whereas limiting warming through lower emissions pathways achieves greater reductions in exposure in central and east Africa ( [[#Rohat--2019|Rohat et al., 2019]] ).

The African population exposed to compound climate extremes, such as coincident heat waves and droughts or drought followed immediately by extreme rainfall, is projected to increase 47-fold by 2070–2099 compared to 1981–2010 for a scenario with high population growth and 4°C global warming (SSP3/RCP8.5) and only 12-fold for low population growth and 1.6°C global warming (SSP1/RCP2.6), with west, central-east, northeastern and southeastern Africa especially exposed ( [[#Weber--2020|Weber et al., 2020]] ). Coincident heat waves and drought is the compound event to which the most people are projected to be exposed: ~1.9 billion person-events (a 14-fold increase) for SSP1/RCP2.6 and ~7.3 billion person-events (52-fold increase) for SSP3/RCP8.5 ( [[#Weber--2020|Weber et al., 2020]] ).

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<span id="projected-risks-to-electricity-generation-and-transmission"></span>