Climate Model-Based Assessment of Anthropogenic Influence on the 2015-19 Western Cape Drought

Abstract

The recent anthropogenic warming likely caused drying trends over Southern Hemisphere subtropics via Hadley Cell expansion and is expected to increase the characteristics of droughts over South Africa in the future. In recent year, the Western Cape region of South Africa has experienced a severe drought over 2015-19. Understanding of the impact of anthropogenic influence on the 2015/19-like multi-year drought remain limited. Here, we use the multiple ensemble members of historical, greenhouse gas, natural-only forcing runs from five CMIP6 models to quantify the anthropogenic influence on the probability of multi-year drought occurrences. According to the CMIP6 simulations, that anthropogenic greenhouse gas forcing has at least doubled the likelihood of 2015–19 like prolonged droughts over the South African Western Cape, with large cancellation due to other anthropogenic effects, particularly anthropogenic aerosol forcing. The findings of this study suggest a need for further studies of potential sources of predictability of multi-year Western Cape droughts.