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

==== 9.5.6.2 Precipitation ====

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===== 9.5.6.2.1 Observations =====

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Mean annual rainfall increased over parts of Namibia, Botswana and southern Angola during 1980–2015 by between 128 and 256 mm (Figure 9.13b). Since the 1960s, decreasing precipitation trends have been detected over the South African winter rainfall region ( ''high confidence'' ) and the far eastern parts of South Africa ( ''low confidence'' ) ( [[#Engelbrecht--2009|Engelbrecht et al., 2009]] ; [[#Kruger--2017b|Kruger and Nxumalo, 2017b]] ; [[#Burls--2019|Burls et al., 2019]] ; [[#Lakhraj-Govender--2019|Lakhraj-Govender and Grab, 2019]] ; [[#Gutiérrez--2021|Gutiérrez et al., 2021]] ; [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ). The frequency of dry spells and agricultural drought in the region has increased over the period 1961–2016 ( [[#Yuan--2018|Yuan et al., 2018]] ; [[#Seneviratne--2021|Seneviratne et al., 2021]] ), the frequency of meteorological drought increased by between 2.5–3 events per decade since 1961 (Spinoni et al 2019) and the probability of the multi-year drought over the southwestern cape of South Africa increased by a factor of three (95% confidence interval 1.5–6) in response to global warming ( [[#Otto--2018|Otto et al., 2018]] ). The number and intensity of extreme precipitation events have increased over the last century ( [[#Kruger--2017b|Kruger and Nxumalo, 2017b]] ; [[#Ranasinghe--2021|Ranasinghe et al., 2021]] ; [[#Sun--2021|Sun et al., 2021]] ), and in the Karoo region of southern South Africa, long-term station data show an increasing trend in annual rainfall of greater than 5 mm per decade over the period 1921–2015 ( [[#Kruger--2017b|Kruger and Nxumalo, 2017b]] ).

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===== 9.5.6.2.2 Projections =====

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Mean annual rainfall in the summer rainfall region is projected to decrease by 10–20%, accompanied by an increase in the number of consecutive dry days during the rainy season under RCP8.5 ( [[#Kusangaya--2014|Kusangaya et al., 2014]] ; [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ; [[#Lazenby--2018|Lazenby et al., 2018]] ; [[#Maúre--2018|Maúre et al., 2018]] ; [[#Spinoni--2019|Spinoni et al., 2019]] ). The western parts of the region are projected to become drier, with increasing drought frequency, intensity and duration ''likely'' under RCP8.5 ( ''high confidence'' ) (Figures 9.16c, e; 9.14; [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ; [[#Liu--2018b|Liu et al., 2018b]] ; 2018c; [[#Ukkola--2020|Ukkola et al., 2020]] ), including multi-year droughts ( [[#Zhao--2016|Zhao and Dai, 2016]] ; [[#Dosio--2017|Dosio, 2017]] ).

Dryness in the summer rainfall region is expected to increase at 1.5°C and higher levels of global warming ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ) and together with higher temperatures will enhance evaporation from the region’s mega-dams and reduce soil-moisture content ( [[#9.7.1|Section 9.7.1]] ; [[#Engelbrecht--2015|Engelbrecht et al., 2015]] ). Increases in drought frequency and duration are projected over large parts of southern Africa at GWL 1.5°C ( [[#Liu--2018b|Liu et al., 2018b]] ; 2018c; [[#Seneviratne--2021|Seneviratne et al., 2021]] ) and unprecedented extreme droughts (compared to the 1981–2010 period) emerge at GWL 2°C ( [[#Spinoni--2021|Spinoni et al., 2021]] ). Meteorological drought duration is projected to increase from approximately 2 months during 1950–2014 to approximately 4 months in the mid-to-late-21st century future under RCP8.5 ( [[#Ukkola--2020|Ukkola et al., 2020]] ). Heavy precipitation in the southwestern region is projected to decrease ( [[#Donat--2019|Donat et al., 2019]] ) and increase in the eastern parts of southern Africa at all warming levels ( [[#Li--2021|Li et al., 2021]] ; [[#Seneviratne--2021|Seneviratne et al., 2021]] ).

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