Abstract
Anthropogenic forcing of the climate is estimated to have increased the likelihood of the 2015–2017 Western Cape drought, also called ‘Day Zero’ drought, by a factor of three, with a projected additional threefold increase of risk in a world with 2 °C warming. Here, we assess the potential for geoengineering using stratospheric aerosols injection (SAI) to offset the risk of ‘Day Zero’ level droughts in a high emission future climate using climate model simulations from the Stratospheric Aerosol Geoengineering Large Ensemble Project. Our findings suggest that keeping the global mean temperature at 2020 levels through SAI would offset the projected end century risk of ‘Day Zero’ level droughts by approximately 90%, keeping the risk of such droughts similar to today’s level. Precipitation is maintained at present-day levels in the simulations analysed here, because SAI (i) keeps westerlies near the South WesternCape in the future, as in the present-day, and (ii) induces the reduction or reversalof the upward trend in southern annular mode. These results are, however,specific to the SAI design considered here because using different model,different SAI deployment experiments, or analysing a different locationmight lead to different conclusions.
Highlights
Extreme weather and climate events are pathways through which climate change impacts are, and will continue to be, felt (Lavell et al 2012)
We used the return period calculated from the observational data and the normal distribution fitted to individual models’ series of 3 year rainfall means in present-day climate (PRST) simulations to determine the model-specific rainfall amount associated with the ‘Day Zero’ event
These results suggest that stratospheric aerosols injection (SAI) would significantly contribute to reducing the likelihood of ‘Day Zero’ level droughts, caused by human-induced climate change over the South Western Cape, by keeping its likelihood in the future in the range of the presentday climate
Summary
Stratospheric Aerosol Geoengineering could lower future risk of ‘Day Zero’ level droughts in Cape Town. Romaric C Odoulami , Mark New , Piotr Wolski , Gregory Guillemet, Izidine Pinto , Christopher Lennard , Helene Muri and Simone Tilmes
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