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

== Atlas.4 Africa ==

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The assessment in this section focuses on changes in average temperature and precipitation (rainfall and snow), including the most recent years of observations, updates to observed datasets, the consideration of recent studies using CMIP5 and those using CMIP6 and CORDEX simulations. Assessment of changes in extremes is in [[IPCC:Wg1:Chapter:Chapter-11|Chapter 11]] (Tables 11.4–11.6) and climatic impact-drivers in [[IPCC:Wg1:Chapter:Chapter-12|Chapter 12]] (Tables 12.1–12.12).

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=== Atlas.4.1 Key Features of the Regional Climate and Findings from Previous IPCC Assessments ===

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==== Atlas.4.1.1 Key Features of the Regional Climate ====

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Africa has many varied climates which can be categorized as dry regime in the Saharan region, tropical humid regime in West and East Africa except for parts of the Greater Horn of Africa (alpine) and the Sahel (semi‐arid), and a dry/wet season regime in the northern and southern African region including the Namib and Kalahari deserts; each climate region has its local variations resulting in very high spatial and temporal variations ( [[#Peel--2007|Peel et al., 2007]] ). Based on the varied climates, nine sub-regions are defined for Africa (Figure Atlas.1 6): the Mediterranean region (MED) including North Africa, Sahara including parts of the Sahel (SAH), West Africa (WAF), Central Africa (CAF), North Eastern Africa (NEAF), South Eastern Africa (SEAF), West Southern Africa (WSAF), East Southern Africa (ESAF) and Madagascar (MDG).

The climatic features that characterize the intra-seasonal and interannual variability of Africa are mainly the Madden–Julian Oscillation (MJO), which is confined to the deep tropics during boreal winter, Pacific Decadal Variability (PDV), and the shift of the Atlantic Inter-tropical Convergence Zone in response to changes in the meridional SST gradient. A positive phase of PDV weakens African monsoons (Figure AIV.8d; [[#Meehl--2006|Meehl and Hu, 2006]] ), and MJO phase 4 suppresses convection over equatorial Africa (Figure AIV.10a; see Annex IV). Other features influence specific sub-regions. For instance, El Niño events increase precipitation in eastern Africa and decrease precipitation in southern Africa. Over southern Africa there is a strong link between ENSO and droughts ( [[#Meque--2015|Meque and Abiodun, 2015]] ). The positive phase of the Indian Ocean Dipole (IOD) increases rainfall in eastern tropical Africa in boreal autumn to early winter (Figure AIV.5d), while the negative phase induces the reduction in rainfall. The West African Monsoon is influenced by Atlantic Zonal Mode (AZM) with decreased rainfall over the Sahel and increased rainfall over Guinea ( [[#Losada--2010|Losada et al., 2010]] ). Positive Atlantic Multi-decadal Variability (AMV) influences positive anomalies all year round over a broad Mediterranean region, including North Africa.

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==== Atlas.4.1.2 Findings From Previous IPCC Assessments ====

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The most recent IPCC reports, AR5 and SR1.5 ( [[#Christensen--2013|Christensen et al., 2013]] ; [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ), state that over most parts of Africa, minimum temperatures have warmed more rapidly than maximum temperatures during the last 50 to 100 years ( ''medium confidence'' ). In the same period, minimum and maximum temperatures have increased by more than 0.5°C relative to 1850–1900 ( ''high confidence'' ). While the quality of ground observational temperature measurements tends to be high compared to that of measurements for other climate variables, Africa remains an under-represented region as reported in SR1.5 ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ; [[#IPCC--2018c|IPCC, 2018c]] ). Based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble and reported in IPCC AR5 and SR1.5, surface air temperatures in Africa are projected to rise faster than the global average increase and are ''likely'' to increase by more than 2°C and up to 6°C by the end of the century, relative to the late 20th century, if global warming reaches 2°C ( [[#Bindoff--2013|Bindoff et al., 2013]] ; [[#Niang--2014|Niang et al., 2014]] ; [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). The higher temperature magnitudes are projected during boreal summer. Southern Africa is ''likely'' to exceed the global mean land surface temperature increase in all seasons by the end of the century. Temperature projections for East Africa indicate considerable warming under RCP8.5 where average warming across all models is approximately 4°C by the end of the century. According to SROCC, eastern Africa like other regions with smaller glaciers is projected to lose more than 80% of its glaciers by 2100 under RCP8.5 ( ''medium confidence'' ) ( [[#Hock--2019b|Hock et al., 2019b]] ).

West Africa has also experienced an overall reduction of rainfall over the 20th century, with a recovery towards the last 20 years of the century ( [[#Christensen--2013|Christensen et al., 2013]] ). Over the last three decades rainfall has decreased over East Africa, especially between March and May/June. Projected rainfall changes over Africa in the mid- and late 21st century is uncertain. In regions of high or complex topography such as the Ethiopian Highlands, downscaled projections indicate ''likely'' increases in rainfall and extreme rainfall by the end of the 21st century. However, North Africa and the south-western parts of South Africa are ''likely'' to have a reduction in precipitation.

The consequence of increased temperature and evapotranspiration, and decreased precipitation amount, in interaction with climate variability and human activities, have contributed to desertification in dryland areas in sub-Saharan Africa ( ''medium confidence'' ) as reported in SRCCL ( [[#Mirzabaev--2019|Mirzabaev et al., 2019]] ).

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=== Atlas.4.2 Assessment and Synthesis of Observations, Trends and Attribution ===

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Figure Atlas.11 shows observed trends in annual mean surface temperature and indicates it has been rising rapidly over Africa from 1961 to 2015 and with significant increases in all regions of 0.1°C–0.2°C per decade and higher over some northern, eastern and south-western regions ( ''high confidence'' ) (see also Interactive Atlas). This is confirmed by an independent analysis performed for a longer period (1961–2018) over areas where long-term homogeneous temperature time series are available ( [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ). More specifically over the Horn of East Africa, the long-term mean annual temperature change between 1930 and 2014 showed two distinct but contrary trends: significant decreases between 1930 and 1969 and increases from 1970 to 2014 ( [[#Ghebrezgabher--2016|Ghebrezgabher et al., 2016]] ). North Africa has an overall warming in observed seasonal temperature ( [[#Barkhordarian--2012|Barkhordarian et al., 2012]] ; [[#Lelieveld--2016|Lelieveld et al., 2016]] ) with positive trends in annual minimum and maximum temperatures ( [[#Vizy--2012|Vizy and Cook, 2012]] ). Temperatures over West Africa have increased over the last 50 years ( [[#Mouhamed--2013|Mouhamed et al., 2013]] ; [[#Niang--2014|Niang et al., 2014]] ) with a spatially variable warming reaching 0.5°C per decade from 1983 to 2010 ( [[#Sylla--2016|Sylla et al., 2016]] ). West Africa has also experienced a decrease in the number of cool nights, as well as more frequent warm days and warm spells ( [[#Mouhamed--2013|Mouhamed et al., 2013]] ; [[#Ringard--2016|Ringard et al., 2016]] ). Similarly, East Africa has experienced a significant increase in temperature since the beginning of the early 1980s ( [[#Anyah--2012|Anyah and Qiu, 2012]] ) with an increase in seasonal mean temperature. Over South Africa, positive trends were found in the annual mean, maximum and minimum temperatures for 1960–2003 in all seasons, except for the central interior ( [[#Kruger--2004|Kruger and Shongwe, 2004]] ; [[#Zhou--2010|Zhou et al., 2010]] ; [[#Collins--2011|Collins, 2011]] ; [[#Kruger--2013|Kruger and Sekele, 2013]] ; [[#MacKellar--2014|MacKellar et al., 2014]] ), where minimum temperatures have decreased significantly ( [[#MacKellar--2014|MacKellar et al., 2014]] ). Within inland southern Africa, minimum temperatures have increased more rapidly than maximum temperatures ( [[#New--2006|New et al., 2006]] ).

Most areas lack enough observational data to draw conclusions about trends in annual precipitation over the past century. In addition, many regions of Africa have discrepancies between different observed precipitation datasets ( [[#Sylla--2013|Sylla et al., 2013]] ; [[#Panitz--2014|Panitz et al., 2014]] ). A statistically significant (95% confidence level) decrease in rainfall and the number of rainy days is reported in autumn over the eastern, central and north-eastern parts of South Africa in spring and summer during 1960–2010 ( [[#MacKellar--2014|MacKellar et al., 2014]] ; [[#Kruger--2017|Kruger and Nxumalo, 2017]] ). Central Africa has experienced a significant decrease in total precipitation, which is likely associated with a significant decrease of the length of the maximum number of consecutive wet days ( [[#Aguilar--2009|Aguilar et al., 2009]] ). Furthermore, rainfall decreased significantly in the Horn of Africa ( [[#Tierney--2015|Tierney et al., 2015]] ) with the largest reductions during the long rains season from March to May ( [[#Lyon--2012|Lyon and DeWitt, 2012]] ; [[#Viste--2013|Viste et al., 2013]] ; [[#Rowell--2015|Rowell et al., 2015]] ). Over mountainous areas significant increases are found in the number of rain days around the southern Drakensberg in spring and summer during the period 1960–2010 ( [[#MacKellar--2014|MacKellar et al., 2014]] ). Similarly, southern West Africa is observed to have had more intense rainfall from 1950 to 2014 during the second rainy season of September to November ( [[#Nkrumah--2019|Nkrumah et al., 2019]] ). The Sahel region also had more intense rainfall throughout the rainy season ( [[#Panthou--2014|Panthou et al., 2014]] , 2018a, b; [[#Sanogo--2015|Sanogo et al., 2015]] ; [[#Gaetani--2017|Gaetani et al., 2017]] ; [[#Taylor--2017|Taylor et al., 2017]] ; [[#Biasutti--2019|Biasutti, 2019]] ) during the period 1980–2010. Southern African rainfall shows a significant downtrend of –0.013 mm day <sup>–1</sup> year <sup>–1</sup> in recent decades and –0.003 mm day <sup>–1</sup> year <sup>–1</sup> for longer periods during 1900–2010 ( ''low confidence'' ) ( [[#Jury--2013|Jury, 2013]] ).

Temperature increases over Africa in the 20th century can be attributed to the strong evidence of a continent-wide anthropogenic signal in the warming (Figure 3.9; [[#Hoerling--2006|Hoerling et al., 2006]] ; [[#Min--2007|Min and Hense, 2007]] ; [[#Stott--2010|Stott et al., 2010]] , 2011; [[#Niang--2014|Niang et al., 2014]] ). More specifically over West Africa, the clear emergence of temperature change (Figure Atlas.11) is due to the relatively small natural climate variability in the region which generates narrow climate bounds that can be easily surpassed by relatively small climate changes ( [[#Niang--2014|Niang et al., 2014]] ). Warming over North Africa is largely due to anthropogenic climate forcing ( [[#Knippertz--2003|Knippertz et al., 2003]] ; [[#Barkhordarian--2012|Barkhordarian et al., 2012]] ; [[#Diffenbaugh--2017|Diffenbaugh et al., 2017]] ).

The drying observed over the Sahel in the 1960s to 1970s has been attributed to warming of the South Atlantic SST and southern African drying as a response to Indian Ocean warming ( [[#Hoerling--2006|Hoerling et al., 2006]] ; [[#Dai--2011|Dai, 2011]] ). Enhanced rainfall intensity since the mid-1980s over the Sahel ( [[#Maidment--2015|Maidment et al., 2015]] ; [[#Sanogo--2015|Sanogo et al., 2015]] ) is associated with increased greenhouse gases suggesting an anthropogenic influence ( ''medium confidence'' ) ( [[#Biasutti--2019|Biasutti, 2019]] ). In the last decade, the changes in the timing of onset and cessation of rainfall over Africa have been linked to changes in the progression of the tropical rainband and the Saharan heat low ( [[#Dunning--2018|Dunning et al., 2018]] ; [[#Wainwright--2019|Wainwright et al., 2019]] ). Moreover, later onset and earlier cessation of eastern Africa rainfall is associated with a delayed and then faster movement of the tropical rainband northwards during the boreal spring and northward shift of the Saharan heat low ( [[#Wainwright--2019|Wainwright et al., 2019]] ), driven by anthropogenic carbon emissions and changing aerosol forcings ( ''medium confidence'' ). Over East Africa, the drying trend is associated with an anthropogenic-forced relatively rapid warming of Indian Ocean SSTs ( [[#Williams--2011|Williams and Funk, 2011]] ; [[#Hoell--2017|Hoell et al., 2017]] ); a shift to warmer SSTs over the western tropical Pacific and cooler SSTs over the central and eastern tropical Pacific ( [[#Lyon--2012|Lyon and DeWitt, 2012]] ); multi-decadal variability of SSTs in the tropical Pacific, with cooling in the east and warming in the west ( [[#Lyon--2014|Lyon, 2014]] ); and the strengthening of the 200-mb easterlies ( [[#Liebmann--2017|Liebmann et al., 2017]] ). However, decadal natural variability from SST variations over the Pacific Ocean has also been associated with the drying trend of East Africa ( [[#Wang--2014|Wang et al., 2014]] ; [[#Hoell--2017|Hoell et al., 2017]] ) with an anthropogenic-forced rapid warming of Indian Ocean SSTs ( ''medium confidence'' ).

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=== Atlas.4.3 Assessment of Model Performance ===

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Model development has advanced in the world, but Africa still lags as a focus and in its contribution ( [[#James--2018|James et al., 2018]] ). None of the current generation of global climate models (GCMs) was developed in Africa ( [[#Watterson--2014|Watterson et al., 2014]] ), and the relevant processes in the continent have not been the priority for model development but treated in a one-size-fit-all approach ( [[#James--2018|James et al., 2018]] ) except for a few studies that focused on convective-permitting climate projections ( [[#Stratton--2018|Stratton et al., 2018]] ; [[#Kendon--2019|Kendon et al., 2019]] ). However, there are growing efforts to boost African climate science by running and evaluating climate models over Africa ( [[#Endris--2013|Endris et al., 2013]] ; [[#Kalognomou--2013|Kalognomou et al., 2013]] ; [[#Gbobaniyi--2014|Gbobaniyi et al., 2014]] ; [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ; [[#Klutse--2016|Klutse et al., 2016]] ; [[#Gibba--2019|Gibba et al., 2019]] ).

The CMIP project previously did not result in improved performance for Africa ( [[#Flato--2013|Flato et al., 2013]] ; [[#Rowell--2013|Rowell, 2013]] ; [[#Whittleston--2017|Whittleston et al., 2017]] ) and culling ensembles based on existing metrics for Africa fails to reduce the range of uncertainty in precipitation projections ( [[#Roehrig--2013|Roehrig et al., 2013]] ; [[#Yang--2015|Yang et al., 2015]] ; [[#Rowell--2016|Rowell et al., 2016]] ), but biases over Africa are lower in CMIP6 compared to CMIP5 ( [[#Almazroui--2020c|Almazroui et al., 2020c]] ). Nonetheless, the CMIP5 ensemble has been evaluated over Africa to advance its application for climate research ( [[#Biasutti--2013|Biasutti, 2013]] ; [[#Rowell--2013|Rowell, 2013]] ; [[#Dike--2015|Dike et al., 2015]] ; [[#McSweeney--2016|McSweeney and Jones, 2016]] ; [[#Onyutha--2016|Onyutha et al., 2016]] ; [[#Wainwright--2019|Wainwright et al., 2019]] ) as has, more recently, the CMIP6 ensemble ( [[#Almazroui--2020c|Almazroui et al., 2020c]] ).

Coordinated Regional Downscaling Experiment (CORDEX) regional climate models have been widely evaluated over Africa. They capture the occurrence of the West African Monsoon jump and the timing and amplitude of the mean annual cycle of precipitation and temperature over the homogeneous sub-regions of West Africa ( [[#Gbobaniyi--2014|Gbobaniyi et al., 2014]] ), simulate eastern Africa rainfall adequately ( [[#Endris--2013|Endris et al., 2013]] ), and over southern Africa capture the observed climatological spatial patterns of extreme precipitation ( [[#Pinto--2016|Pinto et al., 2016]] ). They also effectively simulate the phasing and amplitude of monthly rainfall evolution and the spatial progression of the wet season onset over southern Africa ( [[#Shongwe--2015|Shongwe et al., 2015]] ). However, discrepancies and biases in present-day rainfall are reported over Uganda from the RCM-simulated rainfall compared to three gridded observational datasets ( [[#Kisembe--2019|Kisembe et al., 2019]] ). Specifically, they reported that the CORDEX models underestimate the annual rainfall in Uganda and struggle to reproduce the variability of the long and short rainy seasons.

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=== Atlas.4.4 Assessment and Synthesis of Projections ===

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Research over Africa has improved since AR5, and although SR1.5 ( [[#de%20Coninck--2018|de Coninck et al., 2018]] ) has synthesized new information for the continent, there is still not enough literature on specific areas for assessment. CMIP5 and CMIP6 projections (Figure Atlas.1 6) are for continued warming, with median projected regional warming for 2080–2100 compared to 1995–2014 of between 1°C and 2°C under SSP1-2.6/RCP2.6 emissions and exceeding 4°C and in some regions 5°C under SSP5-8.5/RCP8.5 emissions. The central interiors of southern and northern Africa are ''likely'' to warm faster than equatorial and tropical regions (Interactive Atlas). Projections from CMIP5 show that East Africa is ''likely'' to warm by 1.7°C–2.8°C and 2.2°C–5.4°C under the RCP4.5 and RCP8.5 scenarios respectively in the period 2071–2100 relative to 1961–1990 ( [[#Ongoma--2018|Ongoma et al., 2018]] ). Over southern Africa, areas in the south-western region of the sub-continent, covering South Africa and parts of Namibia and Botswana, are projected to experience the largest increase in temperature, which are expected to be greater than the global mean warming ( [[#Maúre--2018|Maúre et al., 2018]] ). A large ensemble of CORDEX Africa simulations have been used to project the impact of 1.5°C and 2°C GWLs ( [[#Klutse--2018|Klutse et al., 2018]] ; [[#Lennard--2018|Lennard et al., 2018]] ; [[#Maúre--2018|Maúre et al., 2018]] ; [[#Mba--2018|Mba et al., 2018]] ; [[#Nikulin--2018|Nikulin et al., 2018]] ; [[#Osima--2018|Osima et al., 2018]] ). While a few studies addressed the whole African continent ( [[#Lennard--2018|Lennard et al., 2018]] ; [[#Nikulin--2018|Nikulin et al., 2018]] ), some focused on specific regions of Africa ( [[#Diedhiou--2018|Diedhiou et al., 2018]] ; [[#Klutse--2018|Klutse et al., 2018]] ; [[#Kumi--2018|Kumi and Abiodun, 2018]] ; [[#Maúre--2018|Maúre et al., 2018]] ; [[#Mba--2018|Mba et al., 2018]] ). CORDEX simulations project robust warming over Africa in excess of the global mean ( [[#Lennard--2018|Lennard et al., 2018]] ; [[#Nikulin--2018|Nikulin et al., 2018]] ), and over West Africa the magnitude of regional warming reaches the 2080–2100 global warming level one to two decades earlier ( [[#Mora--2013|Mora et al., 2013]] ; [[#Niang--2014|Niang et al., 2014]] ; [[#Sylla--2016|Sylla et al., 2016]] ; [[#Klutse--2018|Klutse et al., 2018]] ). Temperature increases projected under RCP8.5 over Sudan and northern Ethiopia imply that the Greater Horn of Africa would warm faster than the global mean relative to 1971–2000 ( [[#Osima--2018|Osima et al., 2018]] ). Over North Africa, summer mean temperatures from CORDEX, CMIP5 (RCP8.5) and CMIP6 (SSP5-8.5) are projected to increase beyond 6°C by the end of the century with respect to the period 1970–2000 ( [[#Schilling--2012|Schilling et al., 2012]] ; [[#Ozturk--2018|Ozturk et al., 2018]] ; [[#Almazroui--2020c|Almazroui et al., 2020c]] ), see also the Interactive Atlas. Note that results for the CORDEX-AFR over the Mediterranean (MED) are consistent with those reported from the CORDEX-EUR dataset (Figure Atlas.24; Section [[#Atlas.1.3|Atlas.1.3]] ), in agreement with [[#Legasa--2020|Legasa et al. (2020)]] .

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[[File:d9420961f942e86c62f8c331dfa9f080 IPCC_AR6_WGI_Atlas_Figure_16.png]]

'''Figure Atlas.16''' '''|''' '''Regional changes over land in annual mean surface air temperature and precipitation relative to the 1995–2014 baseline for the reference regions in Africa (warming since the 1850–1900 pre-industrial baseline is also provided as an offset).''' Bar plots in the left panel of each region triplet show the median (dots) and 10th–90th percentile range (bars) across each model ensemble for annual mean temperature changes for four datasets (CMIP5 in intermediate colours; a subset of CMIP5 used to drive CORDEX in light colours; CORDEX overlying the CMIP5 subset with dashed bars; and CMIP6 in solid colours); the first six groups of bars represent the regional warming over two time periods (near-term 2021–2040 and long-term 2081–2100) for three scenarios (SSP1-2.6/RCP2.6, SSP2-4.5/RCP4.5 and SSP5-8.5/RCP8.5), and the remaining bars correspond to four global warming levels (GWLs: 1.5°C, 2°C, 3°C and 4°C). The scatter diagrams of temperature against precipitation changes display the median (dots) and 10th–90th percentile ranges for the above four warming levels for December–January–February–March (DJFM; middle panel) and June–July–August–September (JJAS; right panel), respectively; for the CMIP5 subset only the percentile range of temperature is shown, and only for 3°C and 4°C GWLs. Changes are absolute for temperature (in °C) and relative (as %) for precipitation. See [[#Atlas.1.3|Atlas.1.3]] for more details on reference regions ( [[#Iturbide--2020|Iturbide et al., 2020]] ) and [[#Atlas.1.4|Atlas.1.4]] for details on model data selection and processing. The script used to generate this figure is available online ( [[#Iturbide--2021|Iturbide et al., 2021]] ) and similar results can be generated in the Interactive Atlas for flexibly defined seasonal periods. Further details on data sources and processing are available in the chapter data table (Table Atlas.SM.15).

Projected rainfall changes over Africa in the mid- and late 21st century are uncertain in many regions, highly variable spatially and with differing levels of model agreements (Figure Atlas.1 6) though with robust projections of decreases in MED and WSAF and increases in NEAF and SEAF by 2080–2100 under high emissions (Interactive Atlas). Some uncertainties are reported over parts of Africa from CORDEX projections ( [[#Dosio--2016|Dosio and Panitz, 2016]] ; [[#Endris--2016|Endris et al., 2016]] ; [[#Klutse--2018|Klutse et al., 2018]] ). For example, large uncertainties are associated with projections at 1.5°C and 2°C of global warming over Central Africa ( [[#Mba--2018|Mba et al., 2018]] ) and over the Sahel ( [[#Gbobaniyi--2014|Gbobaniyi et al., 2014]] ; [[#Sylla--2016|Sylla et al., 2016]] ). Over southern Africa, enhanced warming is projected to result in a reduction in mean rainfall across the region ( [[#Maúre--2018|Maúre et al., 2018]] ), and in particular over the Limpopo basin and smaller areas of the Zambezi basin in Zambia, and also in parts of the Western Cape in South Africa, under a global warming of 2°C. The projections of reduced precipitation in summer rainfall regions of southern Africa are associated with delayed wet season onset in spring ( [[#Dunning--2018|Dunning et al., 2018]] ) due to a northward shift and delayed breakdown of the Congo Air Boundary ( [[#Howard--2020|Howard and Washington, 2020]] ). However, projected rainfall intensity over southern Africa is ''likely'' to increase and be magnified under RCP8.5 compared with RCP4.5 for the period 2069–2098 relative to the reference period 1976–2005 ( [[#Pinto--2018|Pinto et al., 2018]] ). For West Africa, rainfall projection is uncertain because of the contrasting signals from models ( [[#Dosio--2019|Dosio et al., 2019]] ). Nonetheless, West Africa river basin-scale irrigation potential would decline under 2°C of global warming even for areas where water availability increases ( [[#Sylla--2018|Sylla et al., 2018]] ). The western and eastern Sahel are projected as hotspots for delayed rainfall onset dates of about four days and six days causing reduced length of rainy season in the 1.5°C–2°C warmer climates under RCP4.5 and RCP8.5 scenarios ( [[#Kumi--2018|Kumi and Abiodun, 2018]] ). Projected delay in rainfall cessation dates and a longer length of rainy season over the western part of the Guinea coast is ''likely'' under the same scenarios (Figure Atlas.1 6; [[#Sellami--2016|Sellami et al., 2016]] ; [[#Kumi--2018|Kumi and Abiodun, 2018]] ). There is a tendency towards an increase in annual mean precipitation over central Sahel and eastern Africa (Interactive Atlas, Figure Atlas.1 6, ( [[#Nikulin--2018|Nikulin et al., 2018]] ), especially over the Ethiopian Highlands with up to 0.5 mm day <sup>–1</sup> ( [[#Osima--2018|Osima et al., 2018]] ).

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=== Atlas.4.5 Summary ===

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The rate of surface temperature increase has generally been more rapid in Africa than the global average and by at least 0.1°C–0.2°C during 1961–2015 ( ''high confidence'' ). Minimum temperatures have increased more rapidly than maximum temperatures over inland southern Africa ( ''medium confidence'' ). Since 1970, mean temperature over East Africa has shown an increasing trend but showed a decreasing trend in the previous 40 years ( ''medium confidence'' ).

The Horn of Africa has experienced significantly decreased rainfall during the long rains season from March to May ( ''high confidence'' ) and drying trends in this and other parts of Africa are attributable to oceanic influences ( ''high confidence'' ), resulting from both internal variability and anthropogenic causes. Drying over the Sahel in the last century was attributed to an increase in the South Atlantic SST and more recently over southern African as a response to anthropogenic-forced Indian Ocean warming. Drying over East Africa is associated with decadal natural variability in SSTs over the Pacific Ocean. The enhanced rainfall intensity over the Sahel in the last two decades is associated with increased greenhouse gases indicating an anthropogenic influence ( ''medium confidence'' ) ''.''

Relative to the late 20th century, annual mean temperature over Africa is projected to rise faster than the global average ( ''very high confidence'' ) with the increase ''likely'' to exceed 4°C by the end of the century under RCP8.5 emissions. The central interiors of southern and northern Africa are ''likely'' to warm faster than equatorial and tropical regions ( ''high confidence'' ).

There are contrasting signals in the projections of rainfall over some parts of Africa until the end of the 21st century ( ''high confidence'' ) though changes in any given region are generally projected with ''medium confidence.'' In regions of high or complex topography such as the Ethiopian Highlands, downscaled projections indicate increases in rainfall by the end of the 21st century. However, northern Africa and the south-western parts of South Africa are ''likely'' to have a reduction in precipitation under higher warming levels ( ''high confidence'' ). Over Western Africa, rainfall is projected to decrease in the western Sahel sub-region ( ''medium confidence'' ) and increase in the central Sahel sub-region ( ''low confidence'' ) and along the Guinea coast sub-region ( ''medium confidence'' ). Rainfall amounts are projected to increase over Eastern Africa ( ''medium confidence'' ). Southern Africa is projected to have a reduction in annual mean rainfall but increases in rainfall intensity by 2100 ( ''medium confidence'' ).

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