Editing IPCC:AR6/WGI/Chapter-12 (section)

=== 12.4.1 Africa ===

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Previous IPCC assessments results are summarized in Atlas.4.1.1 For the purpose of this assessment the Africa region has been divided in nine sub-regions of which eight – Sahara (SAH), Western Africa (WAF), Central Africa (CAF), North Eastern Africa (NEAF), South Eastern Africa (SEAF), West Southern Africa (WSAF), East Southern Africa (ESAF) and Madagascar (MDG) – are the official AR6 regions (Figure Atlas.2) and one – North Africa – is used in this assessment to indicate the African portion of the Mediterranean region.

Quite a large body of new literature is now available for the African climate as a result of regionally downscaled CORDEX Africa outputs, in particular, providing projections of both the mean climate ( [[#Mariotti--2014|Mariotti et al., 2014]] ; [[#Nikulin--2018|Nikulin et al., 2018]] ; [[#Dosio--2019|Dosio et al., 2019]] ; [[#Teichmann--2021|Teichmann et al., 2021]] ) and extreme climate phenomena ( [[#Giorgi--2014|Giorgi et al., 2014]] ; [[#Nikulin--2018|Nikulin et al., 2018]] ; [[#Dosio--2019|Dosio et al., 2019]] ; [[#Coppola--2021b|Coppola et al., 2021b]] ). CORDEX Africa simulations are assessed in the Atlas, which finds reasonable skill in mean temperature and precipitation as well as important features of regional climate (e.g., timing of monsoon onset in West Africa) although lower performance in Central Africa.

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==== 12.4.1.1 Heat and Cold ====

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'''Mean air temperature:''' The African continent has experienced increased warming since the beginning of the 20th century in regions where measurements allow a sufficient homogeneous observation coverage to estimate trends ( ''high confidence'' ) (Figure Atlas.11). This warming is ''very likely'' attributable to human influence ( [[IPCC:Wg1:Chapter:Chapter-3|Chapter 3]] and Atlas.4.2) at continental scale. Mean annual temperatures have increased at a high rate since the mid-20th century, reaching 0.2°C–0.5°C per decade in some regions such as north, north-eastern, west and south-western Africa (high confidence) (Atlas.4.2 and Figure Atlas.11).

It is ''very likely'' that temperatures will increase in all future emissions scenarios and all regions of Africa (Atlas.4.4). By the end of the century under RCP8.5 or SSP5-8.5, all African regions will ''very likely'' experience a warming larger than 3°C except Central Africa, where warming is ''very likely'' expected above 2.5°C, while under RCP2.6 or SSP1-2.6, the warming remains ''very likely'' limited to below 2°C (Figure Atlas.12). A ''very likely'' warming with ranges between 0.5°C and 2.5°C is projected by the mid-century for all scenarios depending on the region ( ''high confidence'' ). Mean temperatures for all regions are projected to increase with increasing global warming ( ''virtually certain'' ) (Figure Atlas.12).

'''Extreme heat:''' Warm extremes have increased in most of the regions ( ''high confidence'' ), NEAF, SEAF and MDG ( ''medium confidence'' ) and with ''low confidence'' in CAF (Table 11.4). Despite the increasing mean temperature, there is ''low confidence'' ( ''limited evidence'' ) that Africa has experienced increased extreme heat stress trend for agriculture or human health in the last two decades of the 20th century in a few regions such as West Africa, South Africa and North Africa considering the period from 1973 to 2012 ( [[#Knutson--2016|Knutson and Ploshay, 2016]] ).

A substantial increase in heatwave magnitude and frequency over most of the Africa domain is projected for even 2°C global warming ( ''high confidence'' ) (Sections 11.3 and 11.9, and Table 11.4), with potential effects on health and agriculture. The number of days with maximum temperature exceeding 35°C is projected to increase ( [[#Coppola--2021b|Coppola et al., 2021b]] ) in the range of 50–100 days by 2050 under SSP5-8.5 in WAF, ESAF and WSAF and NEAF ( ''high confidence'' ) (Figure 12.4b). Under SSP1-2.6, the change in the number of exceedance days remains limited to about 40–50 days per year at the end of the century in these regions, while it increases by 150 days or more in WAF, CAF for SSP5-8.5 (Figure 12.4a,c; Figure 12.SM.1).

Mortality-related heat stress levels and deadly temperatures are ''very'' ''likely'' to become more frequent in the future in RCP8.5/SSP5-8.5 and RCP4.5/SSP2-4.5 and for a 2°C global warming ( [[#Mora--2017|Mora et al., 2017]] ; [[#Nangombe--2018|Nangombe et al., 2018]] ; [[#Sylla--2018a|Sylla et al., 2018a]] ; [[#Rohat--2019|Rohat et al., 2019]] ; Q. [[#Sun--2019|]] [[#Sun--2019|]] [[#Sun--2019|Sun et al., 2019]] ). In particular the equatorial regions where heat is combined with higher humidity levels, but also North Africa, the Sahel and Southern Africa (Figure 12.4d–f) are among the regions with the largest increases of heat stress ( [[#Zhao--2015|Zhao et al., 2015]] ; [[#Ahmadalipour--2018|Ahmadalipour and Moradkhani, 2018]] ; [[#Coffel--2018|Coffel et al., 2018]] ). Mitigation scenarios make a large difference in frequency of exceedance of high heat stress indices thresholds (e.g., HI &gt; 41°C) by the end of the century (Figure 12.4d–f; [[#Schwingshackl--2021|Schwingshackl et al., 2021]] ). In West Africa and Central Africa, under SSP5-8.5, the expected number of days per year with HI &gt; 41°C will increase by around 200 days while in SSP1-2.6 such exceedances are expected to increase by less than 50 days per year (Figure 12.4; Figure 12.SM.2).

'''Cold spell and frost:''' Africa experiences cold events and frost days that can affect agriculture, infrastructure, health and ecosystems, especially in Southern and North Africa, which have marked cold seasons and mountainous areas. Cold spells have ''likely'' decreased in frequency over subtropical areas. In particular, in North and Southern Africa, the frequency of cold events has ''likely'' decreased in the last few decades (Sections 11.3 and 11.9). There is a ''high confidence'' that cold spells and low target temperatures will decrease in future climates under all scenarios in West, Central and East Africa. Heating degree days will have a substantial decrease by the end of the century for up to about one month under RCP8.5 in North and Southern Africa ( ''high confidence'' ) ( [[#Coppola--2021b|Coppola et al., 2021b]] ).

'''There is''' high confidence '''that extreme heat has increased in frequency and intensity in most African regions. Heatwaves and deadly heat stress and the frequency of exceedance of hot temperature thresholds (e.g., 35°C) will drastically increase by the end of the century''' ( high confidence ''') under SSP5-8.5, but limited increases are expected in SSP1-2.6. Dangerous heat stress thresholds (HI &gt; 41°C) are projected to be crossed more than 200 days more in West and Central Africa under SSP5-8.5, while this increase remains limited to a few tens of days more for SSP1-2.6. Cold spells and frost days are projected to occur less frequently in all scenarios.'''

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[[File:ec270bb71e166b03dbc08e4cca546973 IPCC_AR6_WGI_Figure_12_5.png]]

'''Figure 12.5''' '''|''' '''Projected changes in selected climatic impact-driver indices for Africa.''' Mean change in 1-in-100-year river discharge per unit catchment area (Q100, m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ) from CORDEX-Africa models for 2041–2060 relative to 1995–2014 for RCP8.5. '''(b)''' Shoreline position change along sandy coasts by the year 2100 relative to 2010 for RCP8.5 (metres; negative values indicate shoreline retreat) from the CMIP5-based dataset presented by [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] . '''(c)''' Bar plots for Q100 (m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ) averaged over land areas for the AR6 WGI Reference Regions (defined in Chapter 1). The left-hand column within each panel (associated with the left-hand y-axis) shows the ‘recent past’ (1995–2014) Q100 absolute values in grey shades. The other columns (associated with the right-hand y-axis) show the Q100 changes relative to the recent past values for two time periods (‘mid’ 2041–2060 and ‘long’ 2081–2100) and for three global warming levels (GWLs, defined relative to the pre-industrial period 1850–1900): 1.5°C (purple), 2°C (yellow) and 4°C (brown). The bars show the median (dots) and the 10–90th percentile range of model ensemble values across each model ensemble. CMIP6 is shown by the darkest colours, CMIP5 by medium, and CORDEX by light. SSP5-8.5/RCP8.5 is shown in red and SSP1-2.6/RCP2.6 in blue. '''(d)''' Bar plots for shoreline position change show CMIP5-based projections of shoreline position change along sandy coasts for 2050 and 2100 relative to 2010 for RCP8.5 (red) and RCP4.5 (blue) from [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] . Dots indicate regional mean change estimates and bars show the 5–95th percentile range of associated uncertainty. Note that these shoreline position change projections assume that there are no additional sediment sinks/sources or any physical barriers to shoreline retreat. See Technical ( [[IPCC:Wg1:Chapter:Annex-vi|Annex VI]] for details of indices. Further details on data sources and processing are available in the chapter data table (Table 12.SM.1).

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==== 12.4.1.2 Wet and Dry ====

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'''Mean precipitation:''' Since the mid-20th century, precipitation trends have varied in Africa but notable drying trends are found in eastern, central and north-eastern parts of Southern Africa, Central Africa and in the Horn of Africa (Atlas.4.2).

There is ''high confidence'' in projected mean precipitation decreases in North Africa and West Southern Africa and ''medium confidence'' in East Southern Africa by the end of the 21st century ( [[#Dosio--2019|Dosio et al., 2019]] ; [[#Gebrechorkos--2019|Gebrechorkos et al., 2019]] ; [[#Teichmann--2021|Teichmann et al., 2021]] ; Atlas.4.5). The Western Africa region features a gradient in which precipitation decreases in the west and increases in the east and increase is also projected over Eastern Africa ( ''medium confidence'' ) (Atlas.4.5), with trends in Western Africa affecting the boreal summer monsoon ( [[#Chen--2020|Chen et al., 2020]] ). Increasing precipitation for 1.5°C and 2°C GWLs are found in central and eastern Sahel with ''low confidence'' and the wet signal is getting stronger and more extended for a 3°C and 4°C warmer world (Atlas.4.4).

A change in monsoon seasonality is also reported in Western Africa and Sahel ( ''low confidence'' ) with a forward shift in time (later onset and end; [[IPCC:Wg1:Chapter:Chapter-8#8.2|Section 8.2]] ; [[#Mariotti--2011|Mariotti et al., 2011]] ; [[#Seth--2013|Seth et al., 2013]] ; [[#Ashfaq--2021|Ashfaq et al., 2021]] ). This shift has been associated with a precipitation decrease during the monsoon season attributed to a decrease of African easterly wave activity in the 6–9-day regime ( [[#Mariotti--2014|Mariotti et al., 2014]] ) and a soil precipitation feedback reported in [[#Mariotti--2011|Mariotti et al. (2011)]] .

'''River flood:''' Generally in Africa from 1990 through 2014, annual flood frequencies have fluctuated and there is ''medium confidence'' in an upward trend in flood events occurrences (C.-J. [[#Li--2016|]] [[#Li--2016|]] [[#Li--2016|Li et al., 2016]] ). In particular, over Western Africa, upward trends in hydrological extremes such as maximum peak discharge have ''likely'' occurred during the last few decades (i.e., after 1980) and have caused increased flood events in riparian countries of rivers such as Niger, Senegal and Volta ( ''high confidence'' ) ( [[#Nka--2015|Nka et al., 2015]] ; [[#Aich--2016a|Aich et al., 2016a]] ; [[#Wilcox--2018|Wilcox et al., 2018]] ; [[#Tramblay--2020|Tramblay et al., 2020]] ). In Southern Africa, trends in flood occurrences were decreasing prior to 1980 and increasing afterwards ( ''medium confidence'' ) ( [[#Tramblay--2020|Tramblay et al., 2020]] ).

Under future climate scenarios, the extreme river discharge as characterized by the 30-year return period of 5-day average peak flow is projected to increase by the end of the century for RCP8.5 (more than 10% relative to the 1971–2000 period) for most of the tropical African river basins ( [[#Dankers--2014|Dankers et al., 2014]] ) and a consistent increase of flood magnitude is projected across humid tropical Africa by 2050 for the A1B scenario ( ''medium confidence'' ) (Figure 12.5; [[#Arnell--2013|Arnell and Gosling, 2013]] ). Specifically, in Western Africa there is not a univocal pattern of change for future projections ( [[#Roudier--2014|Roudier et al., 2014]] ); However, under RCP8.5, there is ''medium confidence'' of a projected increase of 20-year flood magnitudes by 2050 in countries within the Niger River basin ( [[#Aich--2016b|Aich et al., 2016b]] ) and ''low confidence'' ( ''limited evidence'' ) of an increase in extreme peak flows and their duration in countries of the Volta River basin by 2050 and 2090 ( [[#Jin--2018|Jin et al., 2018]] ). A significant median change of flood magnitude for the Gambia River (–4.5%) and for the Sessandra (+14.4%) and Niger (+6.1%) are projected under several scenarios between mid- and end-of-century ( [[#Roudier--2014|Roudier et al., 2014]] ). In East Africa, extreme flows are projected to increase for regions within the Blue Nile basin with ''low confidence'' ( ''limited evidence'' ) ( [[#Aich--2014|Aich et al., 2014]] ). However, uncertainty due to the climate scenario dominates the projection of extreme flows ( [[#Aich--2014|Aich et al., 2014]] ; [[#Krysanova--2017|Krysanova et al., 2017]] ) for the Blue Nile and Niger River basins. Averaged over the African continent for different levels of global warming, the present-day 100-year return period flood levels will have a return period of 40 years in 1.5°C and 2°C ( [[#Alfieri--2017|Alfieri et al., 2017]] ) and 21 years for 4°C warmer climate ( [[#Hirabayashi--2013|Hirabayashi et al., 2013]] ; [[#Alfieri--2017|Alfieri et al., 2017]] ).

'''Heavy precipitation and pluvial flood:''' [[IPCC:Wg1:Chapter:Chapter-11|Chapter 11]] found that heavy precipitation intensity and frequency has ''likely'' increased over West and East Southern Africa but there is no evidence due to a lack of studies that any significant trend is observed in any other region. In addition, East Africa has experienced strong precipitation variability and intense wet spells leading to widespread pluvial flooding events hitting most countries including Ethiopia, Somalia, Kenya and Tanzania ( ''medium confidence'' ). Finally, with respect to Southern Africa, heavy precipitations events have increased in frequency ( ''medium confidence'' ).

In West Africa and Central Africa, there is ''high confidence'' that the intensity of extreme precipitation will increase in a future climate under both RCP4.5 and RCP8.5 scenarios and 1.5°C and 2°C GWLs threatening widespread flood occurrences before, during and after the mature monsoon season (Chapter 11). Extreme precipitation intensity is also increasing in several other regions, such as SAH, NEAF, SEAF, ESAF and MDG ( ''high confidence'' ) for 2°C GWL and higher (Chapter 11).

'''Landslides:''' There is an increase in reported landslides in WAF, CAF, NEAF and SEAF in the past decades but with ''limited evidence'' of significant trends ( [[#Gariano--2016|Gariano and Guzzetti, 2016]] ; [[#Haque--2019|Haque et al., 2019]] ). There is ''low confidence'' ( ''limited evidence'' ) of a future increase in landslides in central-eastern Africa, and literature is largely missing to assess this important hazard ( [[#Gariano--2016|Gariano and Guzzetti, 2016]] ).

'''Aridity:''' Section 11.9 assesses ''medium confidence'' in observed long-term declines of soil moisture and aridity indices in several African regions (NAF, WAF). Trends in East Africa are not definitive given uncertain balances between precipitation and potential evaporation ( [[#Kew--2021|Kew et al., 2021]] ). Projected declines in precipitation and soil moisture trends indicate ''high confidence'' in increased aridity over the 21st century in NAF, WSAF and ESAF but ''low confidence'' elsewhere in Africa ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ; see also Figure 12.4j–l; [[#Gizaw--2017|Gizaw and Gan, 2017]] ). A growing number of studies provide further regional context on expanding aridity in several places in East and West Africa, respectively ( [[#Sylla--2016a|Sylla et al., 2016a]] ; [[#Liu--2018b|Liu et al., 2018b]] ; [[#Haile--2020|Haile et al., 2020]] ).

'''Hydrological drought:''' Section 11.9 noted observed decreases in hydrological drought over the Mediterranean ( ''high confidence'' ) and diminished summer river flows in West Africa ( ''medium confidence'' ). Recent regional modelling studies project substantial increases in hydrological drought affecting major West African river basins under 1.5°C and 2°C GWLs and RCP4.5 and RCP8.5 scenarios (Oguntunde et al. 2018, 2020; [[#Sylla--2018b|Sylla et al., 2018b]] ); however, there remains ''low confidence'' in future projections given disagreement with global model runoff projections (e.g., B.I. [[#Cook--2020|]] [[#Cook--2020|Cook et al., 2020]] ). There is ''high confidence'' that a 2°C GWL would see an increase in hydrological droughts in the Mediterranean region, and ''medium confidence'' in increasing hydrological drought conditions in the Southern Africa regions ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ).

'''Agricultural and ecological drought:''' Farmers and food security experts in East Africa have noted spatial extensions in seasonal agricultural droughts in recent decades ( [[#Elagib--2014|Elagib, 2014]] ), but it is difficult to disentangle these trends from climate variability. In Ethiopia, past severe agricultural drought conditions in the northern regions are moderately common events in recent years ( [[#Zeleke--2017|Zeleke et al., 2017]] ). In Southern Africa, the number of ‘flash’ droughts (with rapid onset and durations from a few days to couple of months) have increased by 220% between 1961 and 2016 as a result of anthropogenic warming ( [[#Yuan--2018|Yuan et al., 2018]] ). [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] notes ''medium confidence'' increases in agricultural and ecological drought trends in North, Western and Central Africa as well as both Southern Africa regions. The most striking drought is the Western Cape drought in 2015–2018, a prolonged drought that resulted in acute water shortages ( [[#Wolski--2018|Wolski, 2018]] ; [[#Burls--2019|Burls et al., 2019]] ; [[IPCC:Wg1:Chapter:Chapter-10#10.6.2|Section 10.6.2]] ). Anthropogenic climate change caused a threefold increase in the probability of such a drought to occur (Chapters 10 and 11; [[#Botai--2017|Botai et al., 2017]] ; [[#Otto--2018|Otto et al., 2018]] ). [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] assesses increases in agricultural and ecological drought at 2°C GWL for North Africa and West Southern Africa ( ''high confidence'' ) and for East Southern Africa and Madagascar ( ''medium confidence'' ), with confidence generally rising for higher emissions scenarios ( [[#Sylla--2016b|Sylla et al., 2016b]] ; [[#Zhao--2017|Zhao and Dai, 2017]] ; [[#Diedhiou--2018|Diedhiou et al., 2018]] ; [[#Abiodun--2019|Abiodun et al., 2019]] ; [[#Todzo--2020|Todzo et al., 2020]] ; [[#Coppola--2021b|Coppola et al., 2021b]] ). [[#Liu--2018b|Liu et al. (2018b)]] identified the Southern Africa region as the drought ‘hottest spot’ in Africa in 1.5°C and 2°C global warming scenarios.

'''Fire weather:''' There is ''low confidence'' ( ''low agreement'' ) in recent reductions in fire activity given soil moisture increases in some regions and substantial land use changes ( [[#Andela--2017|Andela et al., 2017]] ; [[#Forkel--2019|Forkel et al., 2019]] ; [[#Zubkova--2019|Zubkova et al., 2019]] ). Days prone to fire conditions are going to increase in all extratropical Africa until the end of the century and fire weather indices are projected to largely increase in North and Southern Africa, where increasing aridity trends occur ( ''high confidence'' ), with an emerging signal well before the middle of the century where drought and heat increase will combine (Chapter 11; [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ; [[#Abatzoglou--2019|Abatzoglou et al., 2019]] ). There is ''low confidence'' ( ''limited evidence'' ) of fire weather changes for other African regions.

'''Total precipitation is projected to decrease in the northernmost''' ( high confidence ''') and southernmost regions of Africa''' ( medium confidence '''), with West and East Africa regions each having a west-to-east pattern of decreasing-to-increasing precipitation''' ( medium confidence '''). Most African regions will undergo an increase in heavy precipitation that can lead to pluvial floods''' ( high confidence '''), even as increasing dry climatic impact-drivers (aridity, hydrological, agricultural and ecological droughts, fire weather) are generally projected in the North Africa and Southern African regions''' ( high confidence ''') and western portions of West Africa''' ( medium confidence ''').'''

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==== 12.4.1.3 Wind ====

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'''Mean wind speed:''' Decreasing trends in wind speeds have occurred in many parts of Africa ( ''low confidence'' due to observations with limited homogeneity) ( [[#McVicar--2012|McVicar et al., 2012]] ; AR5 WGI). There is ''high confidence'' in climate change-induced future decreasing mean wind, wind energy potential and strong winds in North Africa and Mediterranean regions as a consequence of the poleward shift of the Hadley cell ( [[#Karnauskas--2018a|Karnauskas et al., 2018a]] ; [[#Kjellström--2018|Kjellström et al., 2018]] ; [[#Sivakumar--2018|Sivakumar and Lucio, 2018]] ; [[#Tobin--2018|Tobin et al., 2018]] ; [[#Jung--2019|Jung and Schindler, 2019]] ) in the RCP4.5 and RCP8.5 scenarios by the middle of the century or beyond, and for a GWL of 2°C or higher. Over Western Africa and Southern Africa a future significant increase in wind speeds and wind energy potential is expected ( ''medium confidence'' ) (Figure 12.4m–o; [[#Karnauskas--2018a|Karnauskas et al., 2018a]] ; [[#Jung--2019|Jung and Schindler, 2019]] ).

'''Severe wind storm:''' A limited number of studies allow an assessment of past trends in wind storms. In West Africa and specifically in the Sahel band, more intense storms have occurred since the 1980s ( ''low confidence, limited evidence'' ). A persistent and large increase of frequency of Sahelian mesoscale convective storms has been found in several studies ( [[#Panthou--2014|Panthou et al., 2014]] ; C.M. [[#Taylor--2017|]] [[#Taylor--2017|Taylor et al., 2017]] ), with consequences for extreme rainfalls, and potentially extreme winds ( ''low confidence, limited evidence'' ). There is ''low confidence'' of a general increasing trend in extreme winds across Western, Central, Eastern and Southern Africa in a majority of regions by the middle of the century even in high-end scenarios. The frequency of Mediterranean wind storms reaching North Africa, including Medicanes, is projected to decrease, but their intensities are projected to increase, by the mid-century and beyond under SRES A1B, SRES A2 and RCP8.5 ( ''medium confidence'' ) (Chapter 11; [[#Cavicchia--2014|Cavicchia et al., 2014]] ; [[#Walsh--2014|Walsh et al., 2014]] ; [[#Tous--2016|Tous et al., 2016]] ; [[#Romera--2017|Romera et al., 2017]] ; [[#Romero--2017|Romero and Emanuel, 2017]] ; [[#González-Alemán--2019|González-Alemán et al., 2019]] ).

'''Tropical cyclone:''' In the South Indian Ocean, an increase in Category 5 cyclones has been observed in recent decades ( [[#Fitchett--2018|Fitchett, 2018]] ) as in other basins ( [[IPCC:Wg1:Chapter:Chapter-11#11.7|Section 11.7]] ). However, there is a projected decrease in the frequency of tropical cyclones making landfall over Madagascar, South Eastern Africa and East Southern Africa in a 1°C, 2°C and 3°C warmer world ( ''medium confidence'' ) ( [[#Malherbe--2013|Malherbe et al., 2013]] ; [[#Roberts--2015|Roberts et al., 2015]] , 2020; [[#Muthige--2018|Muthige et al., 2018]] ; [[#Knutson--2020|Knutson et al., 2020]] ). There is ''medium confidence'' in general increasing intensities for cyclones in such studies for African regions.

'''Sand and dust storm:''' North Africa and the Sahel, and to a lesser extent Southern Africa, are prone to dust storms, having consequences on health ( [[#Querol--2019|Querol et al., 2019]] ), transmission of infectious diseases ( [[#Agier--2013|Agier et al., 2013]] ; [[#Wu--2016|Wu et al., 2016]] ), and solar power generation and related maintenance costs. There is ''limited evidence'' and ''low agreement'' of secular 20th century trends in wind speeds or dust emissions (limited length of data records, large variability). Dust variations are controlled by changes in surface winds, precipitation and vegetation, which in turn are modulated at multiple time scales by dominant modes of internal climate variability (Chapter 10). In North Africa, wind variability explains both the observed high concentrations between the 1970s and 1980s and lower concentrations thereafter ( [[#Ridley--2014|Ridley et al., 2014]] ; [[#Evan--2016|Evan et al., 2016]] ). Yet, the effect of vegetation changes may not be negligible ( [[#Pu--2017|Pu and Ginoux, 2017]] , 2018).

Changes to the frequency and intensity of dust storms also remain largely uncertain due to uncertainty in future regional wind and precipitation as the climate warms, CO <sub>2</sub> fertilization effects on vegetation ( [[#Huang--2017|Huang et al., 2017]] ), and anthropogenic land use and land-cover change due to land management and invasive species ( [[#Ginoux--2012|Ginoux et al., 2012]] ; [[#Webb--2018|Webb and Pierre, 2018]] ). Dust loadings and related air pollution hazards (from fine particles that affect health) are projected to generally decrease in many regions of the Sahara and Sahel due to the changing winds ( [[#Evan--2016|Evan et al., 2016]] ) and slightly increase over the Guinea coast and West Africa ( ''low confidence'' ) ( [[#Ji--2018|Ji et al., 2018]] ).

'''In summary, there is''' high confidence '''of a decrease in mean wind speed and wind energy potential in North Africa and''' medium confidence '''of an increase in Southern and Western Africa, by the middle of the century regardless of climate scenario or global warming level equal or superior to 2°C,''' high confidence '''of a decrease in frequency of cyclones landing in SEAF, ESAF and MDG, and''' low confidence '''of a general increase in wind storms in most African regions located south of the Sahel. The evolution of dust storms remains largely uncertain.'''

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==== 12.4.1.4 Snow and Ice ====

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'''Snow and glacier:''' African glaciers are located in East Africa and more specifically on Mount Kenya, the Rwenzori Mountains and Mount Kilimanjaro, with glaciers reducing substantially in each region ( ''high confidence'' ) ( [[#Taylor--2006|Taylor et al., 2006]] ; [[#Cullen--2013|Cullen et al., 2013]] ; [[#Chen--2018|Chen et al., 2018]] ; [[#Prinz--2018|Prinz et al., 2018]] ; [[#Wang--2019|Wang and Zhou, 2019]] ). Observation and future projection of African glacier mass changes are assessed in [[IPCC:Wg1:Chapter:Chapter-9#9.5.1%20|Section 9.5.1]] within the low-latitude glacier region, which is one of the regions with the largest mass loss even under low-emissions scenarios (assessment of this region is dominated by glaciers in the South American Andes, however) ( ''high confidence'' ). Glaciers in the low-latitude region will lose 67 ± 42%, 86 ± 24% and 94 ± 13% of their mass by the end of the century for RCP2.6, RCP4.5 and RCP8.5 scenarios respectively ( [[#Marzeion--2020|Marzeion et al., 2020]] ). [[#Cullen--2013|Cullen et al. (2013)]] calculated that even imbalances between the Mount Kilimanjaro glaciers and present-day climate would be enough to eliminate the mountain’s glaciers by 2060. Snow water equivalent and snow cover season duration also decline in the East African mountains, Ethiopian Highlands and [[IPCC:Wg1:Chapter:Atlas|Atlas]] Mountains with climate change ( ''high confidence'' ) ( [[#López-Moreno--2017|López-Moreno et al., 2017]] ).

'''In conclusion, there is''' high confidence '''that African snow and glaciers have very significantly decreased in the last decades and that this trend will continue over the 21st century.'''

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==== 12.4.1.5 Coastal and Oceanic ====

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'''Relative sea level:''' Around Africa, from 1900 to 2018, a new tide gauge-based reconstruction finds a regional mean RSL change of 2.07 [1.36 to 2.77] mm yr <sup>–1</sup> in the South Atlantic and 1.33 [0.80 to 1.86] mm yr <sup>–1</sup> in the Indian Ocean ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of around 1.7 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5). For the period 1993–2018, these RSLR rates, based on satellite altimetry, increased to 3.45 [3.04 to 3.86] mm yr <sup>–1</sup> and 3.65 [3.23 to 4.08] mm yr <sup>–1</sup> respectively ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of 3.25 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5).

Relative sea level rise is ''virtually certain'' to continue in the oceans around Africa. Regional mean RSLR projections for the oceans around Africa range from 0.4–0.5 m under SSP1-2.6 to 0.8–0.9 m under SSP5-8.5 for 2081–2100 relative to 1995–2014 (median values), which is within the range of projected GMSL change ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.3|Section 9.6.3.3]] ). These RSLR projections may, however, be underestimated due to potential partial representation of land subsidence in their assessment ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.2|Section 9.6.3.2]] ).

'''Coastal flood:''' The present-day 1-in-100-year extreme total water level is between 0.1 and 1.2 m around Africa, with values around 1 m or above along the south-west, south-east and central east coasts ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ).

Extreme total water level (ETWL) magnitude and occurrence frequency are expected to increase throughout the region ( ''high confidence'' ) (Figure 12.4p–r and Figure 12.SM.6). Across the continent, the 5th–95th percentile range of the 1-in-100-year ETWL is projected to increase (relative to 1980–2014) by 7–36 cm and by 14–42 cm by 2050 under RCP4.5 and RCP8.5 respectively. By 2100, this range is projected to be 28–86 cm and 43–190 cm under RCP4.5 and RCP8.5 respectively ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ; [[#Kirezci--2020|Kirezci et al., 2020]] ). In terms of ETWL occurrence frequencies, the present-day 1-in-100-year ETWL is projected to have median return periods of around 1-in-10-years to 1-in-20-years by 2050 and 1-in-1-year to 1-in-5-years by 2100 in southern and North Africa and occur more than once per year by 2050 and 2100 in most of East and West Africa under RCP4.5 ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ). The present-day 1-in-50-year ETWL is projected to occur around three times a year by 2100 with an SLR of 1 m in Africa ( [[#Vitousek--2017|Vitousek et al., 2017]] ).

'''Coastal erosion:''' Shoreline retreat rates up to 1 m yr <sup>–1</sup> have been observed around the continent during 1984–2015, except in ESAF, which has experienced a shoreline progradation rate of 0.1 m/r over the same period ( [[#Luijendijk--2018|Luijendijk et al., 2018]] ; [[#Mentaschi--2018|Mentaschi et al., 2018]] ). [[#Mentaschi--2018|Mentaschi et al. (2018)]] report a coastal area losses of 160 km <sup>2</sup> and 460 km <sup>2</sup> over a 30-year period (1984–2015) along the Atlantic and Indian Ocean coasts of the continent. At the more regional level, in Ghana along the Gulf of Guinea about 79% of the shoreline was found to be retreating while 21% was found to be stable or prograding over the period 1974–1996 ( [[#Addo--2016|Addo and Addo, 2016]] ).

Projections indicate that a vast majority of sandy coasts in the region will experience shoreline retreat throughout the 21st century ( ''high confidence'' ), while parts of the ESAF and western MDG coastline are projected to prograde over the 21st century, if present ambient trends continue. Median shoreline change projections (CMIP5), relative to 2010, presented by [[#Vousdoukas--2020b|Vousdoukas et al. (2020b)]] show that, under RCP4.5, shorelines in Africa will retreat by between 30 m (SAH, NEAF, WSAF, ESAF, MDG) and 55 m (WAF, CAF), by mid-century. By the same period but under RCP8.5, the median shoreline retreat is projected to be between 35 m (SAH, NEAF, WSAF, ESAF) and 65 m (WAF, CAF). By 2100, more than 100 m of median retreat is projected in WAF, CAF and SEAF under RCP4.5, while under RCP8.5, more than 100 m of shoreline retreat is projected in all regions except NEAF and WSAF. Under RCP8.5 especially, the projected retreat by 2100 is greater than 150 m in WAF and CAF. The total length of sandy coasts in Africa that is projected to retreat by more than a median of 100 m by 2100 under RCP4.5 and RCP8.5 is about 13,000 km and 17,000 km respectively, an increase of approximately 33%.

'''Marine heatwave (MHW):''' From 1982 to 2016, the coastal oceans of Africa have experienced on average 2–3 MHWs per year, with the coastal oceans around the southern half of the continent experiencing on average 2.5–3 MHWs per year. The average duration was between 5 and 15 days ( [[#Oliver--2018|Oliver et al., 2018]] ). Changes over the 20th century, derived from MHW proxies, show an increase in frequency between 0.5 and 2 MHWs per decade over the region, especially off the Horn of Africa; an increase in intensity per event around Southern Africa; and an increase in MHW duration along the North African coastlines ( [[#Oliver--2018|Oliver et al., 2018]] ).

There is ''high confidence'' that MHWs will increase around Africa. Mean SST, a common proxy for MHWs, is projected to increase by 1°C (2°C) around Africa by 2100, with a hotspot of around 2°C (5°C) along the coastlines of South Africa under RCP4.5 (RCP8.5; Interactive Atlas). Under global warming conditions, MHW intensity and duration will increase in the coastal zones of all sub-regions of Africa ( [[#Frölicher--2018|Frölicher et al., 2018]] ). Projections for SSP1-2.6 and SSP5-8.5 both show an increase in MHWs around Australasia by 2081–2100, relative to 1985–2014 (Box 9.2, Figure 1).

'''In general, there is''' high confidence '''that most coastal- and ocean-related hazards in Africa will increase over the 21st century. Relative sea level rise is''' virtually certain '''to continue around Africa, contributing to increased coastal flooding in low-lying areas''' ( high confidence ''') and shoreline retreat along most sandy coasts''' ( high confidence '''). Marine heatwaves are also expected to increase around the region over the 21st century''' ( high confidence ''').'''

The assessed direction of change in CIDs for Africa and associated confidence levels are illustrated in Table 12.3. No relevant literature could be found for permafrost and hail, although these phenomena may be relevant in parts of the continent.

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'''Table 12.3''' '''|''' '''Summary of confidence in direction of projected change in climatic impact-drivers in Africa, representing their aggregate characteristic changes for mid-century for scenarios RCP4.5, SSP2-4.5, SRES A1B, or above within each AR6 region (defined in Chapter 1), approximately corresponding (for CIDs that are independent of sea level rise) to global warming levels between 2°C and 2.4°C (see [[#12.4|Section 12.4]] for more details of the assessment method).''' The table also includes the assessment of observed or projected time-of-emergence of the CID change signal from the natural interannual variability if found with at least ''medium confidence'' in [[#12.5.2|Section 12.5.2]] .

[[File:cd304a9910c93ec3527dd226ee411456 IPCC_AR6_WGI_Chapter12_Table_12_3.jpg]]

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