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

=== 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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