Water disasters at both ends of the spectrum — dry and wet — are getting more intense as the planet warms, study finds


From long-term droughts to severe floods, 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 are more strongly linked to higher global temperatures than to naturally changing weather patterns such as El Niño and La Niña. This suggests that these extreme events will increase as the climate crisis accelerates, the study says.

The study comes as California is being hit with its 11th atmospheric river so far this season – storms that have brought torrential rain and crushing snow to a region that has been mired in extreme drought for the past several years. These storms have caused significant flooding, mudslides, collapsed bridges and unusable roads.

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

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

The study found 505 extreme wet events and 551 extreme dry events during this period, with about 70% lasting six months or less and about 10% lasting more than a year.

Scientists found that these extreme events have increased in intensity and frequency since 2015, when the trend of record warm years began.

“We thought maybe this was related to global warming, because we know the last seven years or so have been the hottest on record,” Rodell told CNN. “Certainly, there was a significant correlation between this overall global intensity of these events and the temperature record.”

Rodell wanted to be sure of this conclusion, so he ran analyzes to rule out other climate indicators, including the El Niño-Southern Oscillation, which is a natural climate that involves sea temperature changes in the Pacific Ocean that affects weather worldwide .

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

“What I feel most confident about is that as the world warms, we will see the greater global intensity of all wet and dry events increase, meaning they will be more frequent, larger and more severe overall. Rodel said. “What’s happening in a regional sense is a little harder to say for sure.”

Monday’s report found that the most extreme wet event during the study period occurred in 2020 in sub-Saharan Africa, where months of heavy rainfall swelled Lake Victoria – Africa’s largest lake – to the highest levels ever recorded. The rising water flooded homes and affected critical infrastructure such as drinking water, health care facilities and hydropower.

The most severe dry event recorded by the study was in Brazil and Venezuela from 2015 to 2016, which Rodell said “was about twice as severe” as the current drought in the US Southwest in late 2021. The drought seriously threatened hydropower. drained critical reservoirs and reduced crop yields.

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

“This study uses new data to confirm that human-induced warming is driving the climate system toward more extreme extended wet and dry episodes,” he said.

The worst drought ever to plague Brazil's Amazon region drained river levels to record lows in 2015.

United Nations scientists recently concluded that as the climate changes, droughts that might have occurred only once every 10 years or so are now occurring 70% more often. while heavy rains that used to occur once every 10 years now occur 30% more often.

Although 2022 was not included in the study period, huge areas of the world saw extreme events last year, including deadly floods that submerged a third of Pakistan as well as a severe European drought that caused some rivers to drop to historic lows.

Kim Cobb, a climate scientist and director of the Institute for Environment and Society at Brown University, who was not involved in the study, told CNN that the latest research brings “a new lens into our rapidly changing water cycle, connecting many from the headings droughts, floods and fires in this global analysis.’

Dramatic swings between the two extremes – periods of drought and high rainfall – also known as weathering are another phenomenon that scientists warn will happen more often under a warming planet in the coming decades.

California, which is experiencing a historic drought that is causing severe water shortages, has been suddenly hit by heavy rains and snowstorms in recent months.

“This finding really reinforces the trends we see from the analysis of precipitation data and climate model output and in that sense adds important evidence for emergency planning and response, infrastructure planning, agricultural practices and water management. resources under constant heating,” Cobb said. he said.

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

“The study is another way for people to recognize that climate change affects everyone,” he said. “It is not just the temperature that is rising on average around the world, but the actual weather events that have serious effects on people that may be increasing in intensity and frequency.”

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