Global warming is driving more extreme droughts and floods, NASA data shows

Twenty years of global satellite data from NASA show how the extent, duration and severity of extreme droughts and floods have increased alongside warming global temperatures, a new study finds.

The study looked at the timing of such events and where they occur around the world, said study co-author Matthew Rodell, a scientist at NASA’s Goddard Space Flight Center.

Published in the journal Nature Water, the study found a strong correlation between extreme wet and dry events and increases in temperature.

More extreme events — more frequent, larger and more severe — have occurred in recent years, since 2015, which ranked among the 10 hottest on record, Rodell said.

This work adds to a growing body of evidence suggesting that continued warming could cause more frequent, widespread and severe droughts and floods.

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Weather events change

When you have warmer temperatures, you see these more intense events happening and happening more frequently, Rodell said. It is “very likely that as the world continues to warm, we will see more frequent and severe droughts and (periods of increased precipitation).”

Warmer air causes more evaporation during droughts and increases the amount of water available in thunderstorms and other precipitation during wet events.

A USA TODAY survey in 2021 showed that extreme rainfall had increased in the eastern half of the United States, but droughts were becoming more frequent and intense.

Investigation:How a summer of extreme weather reveals a startling change in the way rain falls in America.

Years of studies had predicted this might be the case, but like the survey, most academic studies use rainfall data.

Rodell and Bailing Li, employed by the University of Maryland at the Space Flight Center, used information from NASA satellites. Rodell said the more precise data helps account for underestimations that occur in extreme precipitation data and uncertainties in rain and snow measurements at higher elevations.

What did the scientists do?

• Observed: Changes in terrestrial water storage measured by remote sensing satellites, including groundwater, soil moisture, snow and ice, and surface waters worldwide.
• Find: 505 wet events and 551 extreme drought events from 2002 to 2021, with an average duration of 5 to 6 months.
• Analysis : Monthly temperature records and monthly total intensity of all wet and dry events and compared them.

What did they find?

One of the main findings: a decrease in the frequency of wet events in the United States and an increase in the frequency of dry events, for example the series of droughts in the Southwest since 2012.

Also:

• A “highly correlated” connection between the global average temperature and the intensity of extreme wet and dry events – combining extent, duration and severity.
• A stronger link to temperature than to El Nino or any other circulation pattern.
• A shift from wetter to drier events in southeastern Brazil and a “broad swath stretching from southern Europe through the Middle East and the Arabian Peninsula to southwestern China and Bangladesh”.
• More dry events in sub-Saharan Africa and west-central South America in the first half of the 20 years, and more wet events in the second half.
• A major flood that covered most of central Africa from 2019 and still ongoing at the end of 2021 was three times larger than the next largest wet or dry event over the entire 20-year period.

How precipitation changes in the United States:See how it changed your community

Satellite data versus precipitation data

“People intuitively recognize that extreme events happen more often, but it’s been hard to say for sure,” Rodell said. “Satellite data gives us a new way of looking at things, which gives us some confidence that this is already happening.”

“We’re not always good at measuring extreme rainfall,” he said. And, rain and snow measurements can’t account for evaporation and runoff, and don’t see the “big picture” of the total amount of water gained or lost.

Rodell and Li used satellites known as GRACE satellites, for Gravity Recovery and Climate Experiment. The satellites measure reflected light and monitor each other’s orbits, taking into account the gravitational pull that affects all data collected and measuring their orbits “with incredible precision”.

In the same way that the US Drought Monitor provides regular monitoring of drought conditions in the country, “the approach presented by Rodell and Li can provide regular monitoring of extreme wet and dry events on a global scale,” wrote Melissa Rohde, in an article also published in Nature Water in March.

“Recognizing drought and flood events before they intensify can help water managers respond accordingly to reduce negative impacts,” she said. The Goddard scientists’ approach “can help communicate the urgency of addressing climate change.”

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Dinah Voyles Pulver covers climate and environmental issues for USA TODAY. She can be reached at dpulver@gannett.com or @dinahvp on Twitter.