(ORDO NEWS) — Scientists have predicted that droughts and floods will become more frequent and severe as our planet warms and changes, but detecting this on regional and continental scales has proven difficult.
Now, a new NASA-led study confirms that major droughts and pluvials – periods of excessive rainfall and water accumulation on land – do occur more often.
Two NASA scientists examined 20 years of data from the NASA/German GRACE and GRACE-FO satellites to identify extremes in wetness and drought.
Each year, floods and droughts account for more than 20% of the economic losses caused by extreme weather events in the United States.
The economic impact is similar around the world, although the loss of life tends to be most devastating in poor areas and developing countries.
In the period 2015-2021 – seven of the nine warmest years on record – the frequency of extreme wet and dry events was four per year, up from three per year in the previous 13 years.
This makes sense, the authors say, because warmer air causes more moisture to evaporate from the Earth‘s surface during drought events; warmer air can also hold more moisture, resulting in heavy snowfalls and downpours.
“The idea of climate change can be abstract.
A couple of degrees of warming doesn’t seem like much, but the impact on the water cycle is palpable,” said Matt Rodell, study co-author and hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“Global warming will lead to more intense droughts and wet spells, affecting people, economies and agriculture around the world.
Monitoring extreme hydrological events is important for preparing for, mitigating and adapting to future events.”
Rodell and study co-author Bailing Li of Goddard studied 1,056 extreme wet and dry events from 2002 to 2021 observed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow-On (GRACE-FO) satellites.
Satellites use accurate measurements of the Earth’s gravity field to detect anomalies in water storage – in particular, how much water stored in soils, aquifers, lakes, rivers, snow cover and ice is compared to normal.
Because GRACE and GRACE-FO provide a new map of water storage anomalies around the world each month, they provide a complete picture of the severity of hydrological events and how they evolve over time.
The most intense event identified in the study was a pluvial that began in 2019 in Central Africa and is still ongoing. This caused the level of Lake Victoria to rise by more than one metre.
The 2015-2016 drought in Brazil was the worst drought event in the past two decades, emptying reservoirs and cutting off water supplies in some Brazilian cities.
“Both events were linked to climate variability, but the drought in Brazil occurred in the warmest year on record (2016), reflecting the impact of global warming.
“Global warming has had wide and deep impacts on the earth’s water supply, such as the reduction in annual snowfall at high altitudes and the depletion of groundwater by humans when surface water is scarce,” said Bailing Li, a hydrologist at the University of Maryland at Goddard.
“By reflecting these changes, the GRACE data gives us a unique perspective on how extreme hydrological events around the world have changed.”
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