New Delhi: A new study has identified an emerging natural process underlying the most extreme heatwaves in mid-latitudes, including northwestern India, in which soil moisture, atmospheric pressure and temperature interact to drive higher temperatures.
Researchers explained that high-pressure systems allow more solar radiation to reach the Earth's surface, heating up the land.
A high-pressure system is a surface area where the atmospheric pressure is higher than the surrounding area.
Likewise, they said, as temperatures rise, soils gradually dry out, reducing their ability to cool the surface through evaporation, which causes the land to heat.
"The two-way relationship between rising temperatures and drying soils has been understood for a while and is already factored into what we expect from a typical extreme heat event," lead author Yinglin Tian, scientist at Potsdam Institute for Climate Impact Research (PIK), said.
"But when we look at these mega heatwaves that have been significantly outstripping previous temperature records, what we're seeing is that once you reach a certain temperature, all three factors: drying soils, high pressure and extreme heat, begin to interact and drive each other further in a way that we haven't understood before," Tian said.
The analysis, published in the journal Science Advances, shows that as the world has warmed from climate change, it has become more likely that the temperature threshold at which this dynamic is triggered is exceeded, forming a vicious cycle, wherein rising temperatures spark off natural processes that cause mercury to climb even further.
Local temperature records have been shattered in heatwave hotspots where "mega heatwaves" have been increasing in frequency faster than more moderate extreme heat events in recent years.
The heatwave hotspots are concentrated in central and eastern Europe, southern Russia and Mongolia, eastern and northwestern North America, northwestern India, the western coast of South America, central and southern Africa, and northern interior Australia.
"We show that a three-way interaction among these components becomes active once a critical temperature threshold is exceeded, contributing, on average, (nearly) 10 per cent to peak temperature anomalies during the most extreme heat events across (nearly) 28 per cent of humid mid-latitude regions," the authors wrote.
The interaction could be systematically underestimated in global climate models, including Coupled Model Intercomparison Project Phase 6, they said.
Soils in the climate models are too dry when heat waves are triggered, thereby suppressing subsequent soil-moisture depletion and inhibiting feedback activation, the team said.
They added the findings help explain regional biases in the models related to upper-tail warming, whereby temperatures on the hottest days of a year increase at a significantly faster rate than average or typical temperatures.
"If we're right and this interaction is making the most extreme heat events even hotter, it means we could be in store for more severe future heatwave risks than what is currently expected," co-author Kai Kornhuber, from the International Institute for Applied Systems Analysis in Austria, said.
This report was published from a wire feed. Apart from the headline, the EdexLive Desk has not edited the copy.