Water disasters at both ends of the spectrum — dry and wet — are intensifying as the planet warms, research shows


From prolonged droughts to severe flooding, the intensity of water-related disasters around the world has increased over the past two decades as global temperatures have risen to record levels, according to new research.

The study by NASA scientists, published Monday in the journal Nature Water, found that increasingly frequent, widespread and intense droughts and floods were more strongly linked to higher global temperatures than to naturally changing weather patterns, such as El Niño and La Niña. This suggests these intense events will increase as the climate crisis accelerates, the study says.

The study comes as California is hit by its 11th atmospheric river so far this season — storms that have brought heavy rainfall and crushing snow in a region that has been mired in extreme drought in recent years. These storms have resulted in significant flooding, mudslides, collapsed bridges and unusable roads.

Although scientists have predicted that climate change will increase the frequency of droughts and floods, it has been difficult to measure.

Matthew Rodell, lead author of the study and a hydrologist at NASA Goddard Space Flight Center, looked at 20 years of NASA satellite data from 2002 to 2021 and analyzed the magnitude, duration and severity — how much wetter or drier it is than normal — of water-related extreme events over worldwide.

The study identified 505 extremely wet events and 551 extremely dry events during this period, about 70% of which lasted six months or less and about 10% lasted more than a year.

The scientists found that these extreme events have been increasing in intensity and frequency since 2015, when the trend of record warm years began.

“We thought, maybe this has to do with global warming, because we know the last seven years have been the hottest on record,” Rodell told CNN. “Of course there was a significant correlation between this total global intensity of these events and the temperature record.”

Rodell wanted to be sure of this conclusion, so he performed analyzes to rule out other climate indicators, including El Niño-Southern Oscillation, a natural climate pattern that involves changes in sea temperature in the Pacific Ocean and influences global weather.

And in the end, he said the climate change signal was stronger than the other natural indicators.

“What I’m more confident about is that as the world warms, we’re going to see the greater global intensity of all wet and dry events increase, meaning they’ll be more frequent, bigger and more severe overall,” Rodell said. happening in a regional sense is a bit more difficult to say with certainty.”

Monday’s report found that the most extreme wet event during the study period occurred in 2020 in sub-Saharan Africa, where months of intense rainfall caused Lake Victoria – Africa’s largest lake – to swell to the highest levels ever recorded. Rising water flooded homes and hit critical infrastructure such as drinking water, healthcare facilities and hydropower.

The most intense dry event the study recorded was in Brazil and Venezuela from 2015 to 2016, which Rodell said was “about twice as intense” as the current drought in the U.S. Southwest as of late 2021. The drought constituted a severe threat to hydroelectric power, critical reservoirs drained and crop yields reduced.

Richard Seager, a professor at Columbia University’s Lamont-Doherty Earth Observatory who was not involved in the study, told CNN that the scientists’ use of satellites to analyze water events was a new angle, since most studies have only measured levels of measure precipitation or soil. moisture.

“This study uses new data to confirm that human-induced warming is driving the climate system towards more extremes of both prolonged and dry spells,” he said.

The worst drought ever to hit Brazil's Amazon region sent river levels to an all-time low in 2015.

UN scientists recently concluded that as the climate changes, droughts that may have only happened once every 10 years are now 70% more common; while heavy rainfall that used to occur once every 10 years now occurs 30% more often.

Although 2022 is not included in the study period, large parts of the world experienced extreme events last year, including the deadly floods that submerged a third of Pakistan and the severe European drought that sent some rivers to historic lows .

Kim Cobb, a climate scientist and director of the Institute for Environment and Society at Brown University who was not part of the study, told CNN that the latest research “brings a new lens on our rapidly changing water cycle, turning many of the headlines about droughts, floods and wildfires to this global analysis.”

Dramatic swings between the two extremes — periods of drought and high precipitation — known as weather whiplash, is another phenomenon that scientists warn will become more common in coming decades under a warming planet.

California, which has endured a historic mega-drought that has led to severe water shortages, has suddenly been pummeled by torrential rain and blizzards in recent months.

“This finding really reinforces the trends we’re seeing from analysis of rainfall data and climate model outputs, and in that sense adds significant evidence for contingency planning and response, infrastructure planning, agricultural practices and water management to sustained warming,” says Cobb. said.

Rodell added that he hopes the study will help people realize that every small rise in global temperatures matters and that the world needs to curb the relentless increase in global warming.

“The study is another way for people to recognize that climate change affects everyone,” he said. “It’s not just about the average temperature increase around the world, it’s the actual weather events that are seriously affecting people and potentially increasing in intensity and frequency.”

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