Internally Driven Variability of the Angola Low is the Main Source of Uncertainty for the Future Changes in Southern African Precipitation.

Variations in southern African precipitation have a major impact on local communities, increasing climate‐related risks and affecting water and food security, as well as natural ecosystems. However, future changes in southern African precipitation are uncertain, with climate models showing a wide range of responses from near‐term projections (2020–2040) to the end of the 21st century (2080–2100). Here, we assess the uncertainty in southern African precipitation change using five Ocean‐Atmosphere General Circulation single model initial‐condition large ensembles (30–50 ensemble members) and four emissions scenarios. We show that the main source of uncertainty in 21st Century projections of southern African precipitation is the internal climate variability. In addition, we find that differences between ensemble members in simulating future changes in the location of the Angola Low explain a large proportion (∼60%) of the uncertainty in precipitation change. Together, the internal variations in the large‐scale circulation over the Pacific Ocean and the Angola Low explain ∼64% of the uncertainty in southern African precipitation change. We suggest that a better understanding of the future evolutions of the southern African precipitation may be achieved by understanding better the model's ability to simulate the Angola Low and its effects on precipitation. Plain Language Summary: The variability of precipitation in southern Africa has a strong impact on local communities, rain‐fed agriculture, food security and water demand, hydropower production, lake levels, ecosystems, and wildlife. Above‐average rainfall increases the risk of flooding, while below‐average rainfall increases the risk of drought. However, future changes in precipitation in southern Africa are poorly understood. Here, we examine the potential sources of uncertainty in southern African precipitation change using five ocean‐atmosphere general circulation single‐model initial‐condition large ensembles and four emissions scenarios. We show that the main source of uncertainty is the simulation of internal climate variability throughout the 21st century. Among potential drivers, we show that the main driver of uncertainty in southern African precipitation change is the future change in the location of the Angola low. A future northward (southward) shift of the Angola Low is associated with a future decrease (increase) in southern African precipitation. We suggest that a better understanding of future changes in southern African precipitation could be achieved by better understanding the impact of internal climate variability on the Angola Low. Key Points: Future changes in southern African precipitation are uncertainThe main source of uncertainty in simulating southern African precipitation change is internal climate variabilityFuture changes in southern African precipitation depend on internal variations in the meridional location of the Angola Low [ABSTRACT FROM AUTHOR]