The Cape Town “Day Zero” drought was caused by an exceptional 3-year rainfall deficit. Combined with management practices and infrastructure shortcomings, the drought caused one of the most serious water crises ever experienced in any heavily populated metropolitan area, with extensive economic impacts. Through the use of a higher-resolution climate model, a new analysis further constrains previous work showing that anthropogenic climate change made this event five to six times more likely relative to the early 20th century.
The authors of the study, led by former AOS Associate Research Scholar Salvatore Pascale (Stanford University) with support from CIMES, provide a clear and well-supported mechanism for the increase in drought risk in southwestern South Africa (SSA) through a dedicated analysis of the circulation response, which highlights how—as in 2015–2017—a reduction in precipitation during the shoulder seasons is likely to be the cause of drought risk in SSA in the 21st century. Sarah Kapnick '04, a physical scientist at GFDL and former AOS postdoc, AOS Faculty Member Tom Delworth (GFDL) and William Cooke (GFDL) are co-authors of the study. The paper was recently published in PNAS.