Twenty years of NASA’s global satellite data show just how much the extent, duration and severity of extreme droughts and floods have risen alongside warming global temperatures, a new study reveals.
The study looked at the timing of such events and where they’re happening 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 temperature increases.
More extreme events — more frequent, bigger and more severe — occurred in the later years, since 2015, which have ranked among warmest top 10 on record, Rodell said.
Weather events are changing
When you have warmer temperatures, you see these more intense events happening, and happening more frequently, Rodell said. It’s “highly likely that as the world continues to warm, we will see more frequent and more severe droughts and (periods of increased rainfall).”
Warmer air causes more evaporation during droughts and increases the amount of water available in thunderstorms and other precipitation during wet events.
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 underestimates that occur in extreme precipitation data and for uncertainties in rain and snow measurements at higher elevations.
Floodwaters cover an agriculture area in California after the Salinas River overflowed its banks as atmospheric rivers pounded California in January. (Photo by Justin Sullivan/Getty Images)
What did the scientists do?
Observed: Changes in land-based water storage measured by remote-sensing satellites, including groundwater, soil moisture, snow and ice and surface waters around the world.
Found: 505 wet events and 551 extreme dry events from 2002-2021, with an average duration of 5-6 months.
Analyzed: Monthly temperature records and monthly total intensity of all wet and dry events and compared them.
What did they find?
One of the key findings: A decrease in frequency of wet events in the U.S. and an increased frequency of dry events, for example the series of droughts in the Southwest since 2012.
Also:
A “highly correlated’ connection between global mean temperature and the intensity of extreme wet and dry events – combining extent, duration, and severity.
A stronger connection with temperature than with El Nino or any other circulation patterns.
A shift from more wet events to more dry events in Southeastern Brazil and within a “vast swath from southern Europe across the Middle East and Arabian Peninsula to south-western China and Bangladesh.”
More dry events in sub-Saharan Africa and west central South America during the first half of the 20 years, and more wet events in the second half.
A big flood event that covered most of Central Africa starting in 2019 and still ongoing at the end of 2021 was three times as large as the next biggest wet or dry event in the entire 20-year span.