‘A new climatic regime’
By Summit Voice
FRISCO — The number of severe heatwaves could double by 2020 and quadruple by 2040, according to a team of German and Spanish scientists who fine-tuned a set of climate models to try and reduce uncertainty. In the second half of the century, even higher frequencies are expected unless greenhouse gas emissions are reduced.
“In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today. That’s what our calculations show for a scenario of unabated climate change,” said Dim Coumou, of the Potsdam Institute for Climate Impact Research. “We would enter a new climatic regime.”
The scientists focused on heat waves that exceed the usual natural variability of summer month temperatures in a given region by a large margin. These are periods of several weeks that are three standard deviations warmer than the normal local climate — often resulting in harvest losses, forest fires, and additional deaths cities.
Extreme heatwaves could affect 85 percent of the global land area in summer by 2100, if CO2 continues to be emitted as it is today, the study shows. Even hotter extremes, virtually non-existent today, would affect 60 percent of the global land area.
While climate change mitigation could prevent this, the projected increase up to mid-century is expected to happen regardless of future emissions scenarios. Current concentrations of heat-trapping gases all but guarantee extreme heatwaves in the short-term future, Coumou said.
The study defines a heat extreme based on the natural variability a region has experienced in the past, so absolute temperatures during heatwaves will differ in different regions of the world. The observed Russian heatwave in 2010 brought an increase of the monthly average temperature by 7 degrees Celsius in Moscow and daily peak temperatures above 40 degrees. In tropical regions like Southern India or Brazil, natural variability is much smaller than in the moderate zones, hence extreme events are not as large a deviation in absolute temperatures.
“In general, society and ecosystems have adapted to extremes experienced in the past and much less so to extremes outside the historic range,” said Alexander Robinson of Universidad Complutense de Madrid. “So in the tropics, even relatively small changes can yield a big impact — and our data indicates that these changes, predicted by earlier research, in fact are already happening.”
We show that these simulations capture the observed rise in heat extremes over the past 50 years very well.” Robinson said. “This makes us confident that they’re able to robustly indicate what is to be expected in future.”
Filed under: climate and weather, global warming Tagged: | climate change, Complutense University of Madrid, extreme weather, global warming, Greenhouse gas, heatwaves, Potsdam Institute for Climate Impact Research