NASA: Drought, wet events become more frequent and intense as global warming: NASA-led study

NEW DELHI: Major droughts and pluvials – periods of excessive rainfall and accumulation of water on land – are indeed more common, confirms a new study led by the National Aeronautics and Space Administration (NASA).
Scientists predict that as our planet warms and the climate changes, droughts and floods will become more frequent and severe, but this has been difficult to determine at regional and continental scales, the study said.
In a study published in the journal Nature Water, two scientists from NASA, USA, examined 20 years of data from the NASA/German GRACE and GRACE-FO satellites to identify extreme wet and dry events.
Floods and droughts account for more than 20 percent of economic losses from extreme weather events in the United States each year. The economic impacts are the same worldwide, although the human toll is most devastating in poor areas and developing countries.
The scientists also found that the worldwide intensity of these extreme wet and dry events—a measure that combines the extent, duration, and severity—is closely related to global warming.
Between 2015 and 2021—seven of the nine warmest years on record—the frequency of extreme wet and dry events was four per year, compared with three in the previous 13 years.
This makes sense, the authors say, because warm air causes more moisture to evaporate from the surface during dry events; warm air can also hold more moisture to burn heavy snow and precipitation.
“The idea of ​​climate change can be abstract. A couple of degrees of warming doesn’t sound like much, but the effect of the water cycle is felt,” he said. Matt RodellCo-author of the study at NASA.
“Global warming is causing severe droughts and wet periods that affect people, economies and agriculture around the world. Monitoring hydrological emergencies is important for preparing for, mitigating and adapting to future events,” Rodell said.
Rodell and co-author of the study Bailing Li It examined 1,056 extreme wet and dry events from 2002 to 2021, as observed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow-On (GRACE-FO) satellites.
The satellites use accurate measurements of the Earth’s gravity field to detect water storage anomalies, specifically how the amount of water stored in soil, aquifers, lakes, rivers, snowpack and ice compares to normal levels, the study said.
“It’s like controlling the water level in a bathtub.
“You can see how much it rises and falls without knowing the total amount of water in the tub,” Rodell said.
Because GRACE and GRACE-FO provide a new map of water storage anomalies around the world every month, they provide a comprehensive picture of the severity of hydrological events and how they evolve over time, the study said.
In their study, Rodell and Lee used an “intensity” metric that measures the severity, duration, and spatial extent of drought and extreme wet events.
They found that the overall global intensity of extreme events increased from 2002 to 2021, reflecting an increase in Earth’s temperature over that period.
According to the study, the most intense event identified in the study was a pluvial event that began in Central Africa in 2019 and is still ongoing.
This caused the level of Lake Victoria to rise by more than a meter.
The 2015-2016 drought in Brazil was the most intense in two decades, leaving reservoirs empty and water shortages in some Brazilian cities.
“Both events were linked to climate variability, but the drought in Brazil was the warmest year on record (2016), reflecting the effects of global warming,” Lee said.
“Recent droughts in the southwestern United States and southern Europe have also been among the most intense events due in part to anthropogenic warming,” Lee said.
“Global warming has had far-reaching and profound impacts on surface water conservation, such as reduced annual snowpack at high altitudes and human depletion of groundwater when surface water is scarce,” Lee added.
“By showing these changes, GRACE data gives us a unique perspective on how hydrological extremes have changed around the world,” Lee said.

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