PARIS: The intensity of extreme water cycle events – especially drought and precipitation or flooding – correlates strongly with a continuing rise in global temperatures, according to a study published Monday (Mar 13).
Applying a novel method, researchers used satellite observations to quantify and rank more than a thousand extreme weather events over the last 20 years that have up to now defied easy measurement.
Rainfall and soil moisture – or the lack of it – have previously been the main yardstick for assessing intensity.
“Warm air increases evaporation so that more water is lost during droughts, and warm air also holds and transports more moisture, increasing precipitation during wet events,” co-author Matthew Rodell of NASA told AFP.
“So what we are seeing – greater intensity of extreme wet and dry events as the world warms – makes sense.”
Since 2015, the frequency of the highest category extreme events has increased to four per year, compared to three per year over the previous 13 years, the study reported.
The scientists were nonetheless surprised at how closely the pace of global warming tracked with the intensity of disruptions in the water cycle.
The impact was even stronger than naturally occurring El Nino and La Nina weather phenomena, they reported in the journal Nature Water.
The findings leave little doubt that increasing temperatures will cause more frequent, widespread and severe droughts and precipitation events in the future.
Earth’s surface has warmed, on average, 1.2 degrees Celsius since the late 19th century, and – on current policies – is on track to heat up 2.8 degrees Celsius above that benchmark by 2100.
By far the largest extreme event of the past 20 years was a sustained deluge over central Africa that “dwarfed” all the others measured.
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