Cape Town, South Africa’s second most populated city, came dangerously close to running out of water in 2018, when the country’s reservoirs were depleted by the multi-year “Day Zero” drought. Since then, Stanford University experts have found that climate change has made this level of extreme drought five to six times more likely. They have cautioned that many more Day Zero events may occur in the future in countries with comparable conditions.
In the coming decades, a better understanding of likely surface air temperature and precipitation trends in South Africa and other dry, populated areas around the world could enable decision makers to pursue science-based climate mitigation and adaptation measures to reduce the risk of future Day Zero events.
Researchers from the MIT Joint Program on the Science and Policy of Global Change, the International Food Policy Research Institute and the CGIAR have developed modelled projections of 21st-century changes in seasonal surface air temperature and precipitation for South Africa that account for uncertainties in how Earth and socioeconomic systems behave and co-evolve.
These estimates, which were published in the journal Climatic Vary, illustrate how temperature and precipitation in three sub-national regions of South Africa — western, central and eastern — are projected to change under a variety of global climate mitigation policy scenarios.
In a business-as-usual global climate policy scenario, in which no emissions or climate targets are set or met, the predictions reveal that mid-century temperatures will rise threefold over the current climate’s range of fluctuation for all three regions. However, more aggressive climate targets practically eliminate the likelihood of these mid-century temperature increases.
Dangers of climate change
The probability of decreased precipitation levels in western and central South Africa is three to four times higher than the chance of enhanced precipitation levels, according to business-as-usual estimates.
Higher dependence and stress on broad water-efficiency measures developed in the aftermath of the Day Zero drought, show increased reliance and stress on widespread water-efficiency measures established in the aftermath of the Day Zero drought under a business-as-usual scenario. However, a worldwide climate mitigation policy of 1.5 degrees Celsius would postpone these dangers for 30 years, allowing South Africa plenty of time to prepare and adapt.
“Our analysis provides risk-based evidence on the benefits of climate mitigation policies as well as unavoidable climate impacts that will need to be addressed through adaptive measures,” says MIT joint programme deputy director C. Adam Schlosser, the lead author of the study.
“Global action to limit human-induced warming could give South Africa enough time to secure sufficient water supplies to sustain its population. Otherwise, anticipated climate shifts by the middle of the next decade may well make Day Zero situations more common.”
This research is part of a larger project to examine the dangers that climate change poses to the agricultural, economic, energy and infrastructure sectors in South Africa.
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