Potential impacts of global warming levels 1.5 degrees C and above on climate extremes in Botswana

摘要

Limiting global warming to 1.5 degrees C and 2.0 degrees C above pre-industrial levels has been proposed as a way to reduce the impacts of climate change globally. Formulating reliable policies to adapt to these warming levels requires an understanding of the impacts at regional and national scales. The present study examines the potential impacts of the different global warming levels (1.5 degrees C and above) on climate extremes over Botswana, one of the most vulnerable countries to extreme climate events. Using a series of regional climate model simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), we investigate the impacts of the warming on characteristics of the rainy season (onset, cessation, length, and number of wet days), extreme precipitation, and droughts. The simulations project a short length of the rainy season with a reduced number of wet days over Botswana at all the warming levels. They also indicate more frequent and intensified extreme precipitation, particularly in north-west Botswana. However, the additional rain water from the extreme rainfall may not offset the deficit in rainfall amount induced by the shorter rainy season with fewer wet days. Drought intensity and frequency are also projected to increase, but the magnitude of changes increases with higher warming levels. The policy implications of projected changes are discussed in relation to the possible impacts on society using agriculture and water availability as examples.