0.7–1.25 million years old—The age of plant matter preserved in a column of sediment that was drilled off the coast of South Africa and analyzed in recent research to study the influence of climate change on extreme droughts. The plant samples, from a period known as the Mid-Pleistocene Transition, contained hydrogen isotopes from rainfall that helped researchers reconstruct climate conditions from that time and discover that significant changes in global atmospheric circulation caused extreme wet and dry periods in southern Africa. Specifically, they detected drought conditions similar to those during a 2015–20 drought in Cape Town, South Africa, called the “Day Zero” drought in reference to the day when the city would have run out of municipal water (restrictions to water usage prevented that from happening). “We found that when the climate has changed dramatically in the past, it produced shifts analogous to the Day Zero drought,” explains coauthor Tripti Bhattacharya of Syracuse University. “This suggests that those types of events are really driven by global climate change.” Bhattacharya and colleagues found evidence in the plant matter of contractions and expansions of the Hadley Cell, the global tropical atmospheric overturning circulation in which air rises near the equator and descends in the subtropics, which could have caused shifts in rainfall patterns that produced the extreme drought conditions. The findings, which were published in Nature Communications, provide more insight into the relationship between climate change and drought, which is typically examined with modeling. “But a model is not the real world,” Bhattacharya says. “So we looked back in time.” [Source: Syracuse University]
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