The areas most at risk from extreme rainfall and extreme droughts are being identified by new studies of the amount of water on the Earth’s surface, as well as in its interior, where the most important supply of drinking water is concentrated for the survival of the human species. , located.

The evidence came from data from a NASA satellite mission that found changes in gravity capable of detecting changes in the volume of water even underground. “Until now, we did not have data on groundwater in most countries of the world. The NASA program has made a difference and is giving us data from everywhere,” says Matthew Rodel, second officer at the US space agency’s Goddard Space Center.

In their publication Monday in the journal Nature Water, Dr. Rodel and colleagues analyzed satellite data and recorded 505 “events” of extreme rainfall and 551 extreme droughts between 2002 and 2021, ranking them by intensity, geographic coverage and duration.

The study also found that an increase in the average temperature of the Earth is intensifying the El Niño weather phenomenon, which can dramatically affect temperatures and precipitation in the Pacific Ocean and beyond. The tropical zone is experiencing increasingly intense rainy seasons, while the continental regions of the planet are prone to prolonged drought. However, the scientific community does not consider a 20-year observation period sufficient to make long-term predictions. “Any such study will necessarily be limited in scope. But no one can say that such studies are useless,” says John Fazullo, a researcher at the US National Center for Atmospheric Research who was not involved in the NASA study.

Data from the Grace satellite program, as the space agency’s program is called, show other shortcomings. Global precipitation measurements are recorded once a month and are thus released with a time delay, making early prediction of extreme events nearly impossible. At the same time, the clarity of satellite observations is limited, which makes it difficult to register local phenomena with possible significant effects.

The analysis also excludes geographic areas known to suffer from long-term human impacts, but does not account for the effects of rapid melting of the polar ice caps. However, NASA satellites have surveyed small geographic areas and have confirmed, for example, that groundwater in central California is being depleted due to intensive agriculture.

The disappearance of groundwater remains little studied by the scientific community, although it may be directly related to global warming. “With climate change, heavy rains and droughts will intensify. The study showed this,” says Dr. Fasolo.