Increasing Risk of Another Cape Town “Day Zero” Drought in the 21st Century

Publication Year
2020

Type

Journal Article
Abstract

Three consecutive dry winters (2015–2017) in southwestern SouthAfrica (SSA) resulted in the Cape Town “Day Zero” drought inearly 2018. The contribution of anthropogenic global warmingto this prolonged rainfall deficit has previously been evaluatedthrough observations and climate models. However, model ade-quacy and insufficient horizontal resolution make it difficult toprecisely quantify the changing likelihood of extreme droughts,given the small regional scale. Here, we use a high-resolutionlarge ensemble to estimate the contribution of anthropogenicclimate change to the probability of occurrence of multiyearSSA rainfall deficits in past and future decades. We find thatanthropogenic climate change increased the likelihood of the2015–2017 rainfall deficit by a factor of five to six. The prob-ability of such an event will increase from 0.7 to 25% by theyear 2100 under an intermediate-emission scenario (Shared Socio-economic Pathway 2-4.5 [SSP2-4.5]) and to 80% under a high-emission scenario (SSP5-8.5). These results highlight the strongsensitivity of the drought risk in SSA to future anthropogenic emissions.

Journal
PNAS
Volume
117
Issue
47
Pages
29495-29503
Date Published
November 2020
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