Floods and droughts are intensifying
Nature Water March 2023
A study published in the journal Nature Water on 13 March 2023 finds that extreme rainfall and droughts have increased in frequency, duration and extent on every continent in the last 20 years due to human induced climate change. Warming conditions intensify the water cycle, increasing evaporation during dry events and raising atmospheric moisture that results in heavy precipitation. The global frequency and intensity of events correlated well with the rise in global mean temperatures due to burning fossil fuels and other human releases of greenhouse gases.
The study, which examined over 1,000 events from 2002 to 2021, used satellite data that monitored shifts in Earth's water storage on and in the land, including groundwater, surface water, ice and snow. It then used an algorithm that indicates where the wetness or dryness of land was greater than usual.
The most extreme rains were in sub-Saharan Africa, in central and eastern North America, and for a while in Australia. The most intense droughts were in northeastern South America, the Cerrado region of Brazil, and in the American southwest. Drought events were 10 percent more frequent that heavy rains, but their geographic extent and duration were similar. The swing between extreme drought and unprecedented flooding is called "weather whiplash".
The result of such extreme events is a range of outcomes such as crop failures, infrastructure damage, economic losses, humanitarian crises and conflict. Water stress significantly affects the poor, as with the continuing drought in Somalia, killing millions of livestock and resulting in widespread famine. Many ecosystems are also being damaged.
Continued global warming will mean that drought and rainstorms will be more frequent and severe, both longer and affecting larger areas. Infrastructure that was designed for once-in-a-100-year events will be increasingly challenged. To respond, flood waters can be used to recharge depleted aquifers. Regenerating soil in agriculture so that it can absorb more water and store carbon will also help to increase water resiliency.
Based on Matthew Rodell and Bailing Li. 2023. Changing intensity of hydroclimatic extreme events revealed by GRACE and GRACE-FO. Nature Water, 13 March 2023 https://doi.org/10.1038/s44221-023-00040-5.
Last updated 17 March 2023