Global floods and droughts worsen with warming, study suggests

These are not simply difficult weather events, but are leading to extremes such as crop failure, infrastructure damage and even humanitarian crises and conflicts, according to research published in the journal Nature Water.

The big picture for water comes from data from a pair of satellites known as the Grace, or Gravity Recovery and Climate Experiment, which were used to measure changes in Earth’s water storage: the sum of all the water on and in land, including groundwater, surface water, ice, and snow.

“It’s amazing that we can now monitor the pulse of continental water from outer space,” said Park Williams, a bioclimatologist at the University of California, Los Angeles who was not involved in the study.

People wade through flood waters in the town of Moree in northern New South Wales, Australia
People wade through flood waters in the town of Moree, New South Wales, Australia (Brad Hunter, Pool, AP)

“I have a feeling that when future generations look back and try to determine when humanity really began to understand the planet as a whole, this will be one of the standout studies,” he said.

The researchers say the data confirms that both the frequency and intensity of rainfall and droughts are increasing due to the burning of fossil fuels and other human activities that release greenhouse gases.

“I was surprised to see how well the global intensity was correlated with global mean temperatures,” said Matthew Rodell, study author and deputy director of Earth sciences for hydrosphere, biosphere, and geophysics at NASA’s Goddard Space Flight Center.

The strong link between these weather extremes and rising global average temperatures means that continued global warming will mean more droughts and rainstorms that are worse by many measures: more frequent, more severe, longer, and larger.

The researchers looked at 1,056 events between 2002 and 2021 using a novel algorithm that identifies where the earth is much wetter or drier than normal.

That showed that the most extreme rainfall is still occurring in sub-Saharan Africa, at least until December 2021, the end of the data.

Rainfall extremes also occurred in central and eastern North America between 2018 and 2021, and in Australia during 2011 and 2012.

The most intense droughts were a record in the northeast of South America between 2015 and 2016; an event in the Cerrado region of Brazil that began in 2019 and continues; and the ongoing drought in the American Southwest that has caused dangerously low water levels in two of the largest reservoirs in the United States, Lake Mead and Lake Powell. Those remain low despite heavy rain this year.

Drought events outnumbered heavy rain events by 10%.

Its geographic extent and duration were similar.

A warmer atmosphere increases the rate at which water evaporates during dry spells.

It also contains more water vapor, which fuels heavy rains.

The study noted that infrastructure such as airports and sewage treatment plants that were designed to withstand once-in-a-100-year events face further challenges as these extremes occur more frequently and with greater intensity. .

“Looking ahead, in terms of water resource management and flood control, we should anticipate that the wetter ends will get wetter and the dry ends will get drier,” said Richard Seager, a climate scientist at the Lamont Earth Observatory. Doherty. at Columbia University, who was not involved in the study.

Seager said it’s a mistake to assume that future wet and dry extremes can be handled in the same way as in the past because “everything will be amplified at both ends of the dry-wet spectrum.”

According to the US National Integrated Drought Information System, 20% of annual economic losses from extreme weather events in the US are due to floods and droughts.

People walk across the cracked earth in an area that was once under the water of Lake Mead in the Lake Mead National Recreation Area near Boulder City, Nevada.
People walk along cracked earth in an area that was once under water from Lake Mead in the Lake Mead National Recreation Area near Boulder City, Nev. (John Locher/AP)

A drastic switch between extreme drought and unprecedented flooding, dubbed “whiplash,” is becoming common in some regions.

Water stress is expected to significantly affect poor and disenfranchised communities, as well as ecosystems that have been underfunded and exploited.

For example, the United Nations has said that Somalia is experiencing its longest and most severe drought, an event that has caused the death of millions of cattle and widespread famine.

Venezuela, a country that has faced years of political and economic crisis, resorted to nationwide power cuts during April 2016 as a result of drought conditions that affected the water levels of the Guri dam.

As for solutions, using floodwater to replenish depleted aquifers and improving the health of agricultural soil so it can better absorb water and store more carbon are just a few of the methods that could improve water resilience. in a warming world, says the study.


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