Rise in Extreme Heat Waves Already Locked in for Next 30 Years

The amount of global land affected by extreme heat waves classified as three-sigma events is set to double by 2020 and quadruple by 2040 regardless of changes in the amount of carbon dioxide released into the atmosphere, a study published in Environmental Research Letters reports.

Three-sigma heat waves -- a reference to an average rise in temperature three standard deviations above the norm -- include the hot spell that, in 2010, gripped Russia all the way from the Baltic to the Caspian Sea, during which time temperatures averaged 7 degrees Celsius higher than normal.

Furthermore, the study warns of a rise in five-sigma heat waves from essentially non-existent to covering 3 percent of global land surface by 2040. From there on out, any increase, whether for three or five sigma events, depends on how much CO2 is emitted, the researchers determined.

In the case that emissions are low, frequency will stabilize by 2040; however, should emissions increase, the land affected will increase by 1 percent every year after that. Looking out toward the end of the century, the researchers found three-sigma heat waves will cover 85 percent of the global land area and five-sigma as much as 60 percent by 2100 in the case of high emissions. 

To reach these conclusions, Dim Coumou, from the Potsdam Institute for Climate Impact Research, and Alexander Robinson, from Universidad Complutense de Madrid, relied on climate models that took into account two future warming scenarios known as RCP2.6 and RCP8.5. According to their results, not all parts of the world will be affected evenly with the hardest hit area being tropical regions -- a reality the researchers say can already be detected when analyzing regional data dating from 2000 to 2012.

Ultimately, the scientists report, the implications of a rise in such extreme heat would pose a threat in a wide variety of ways.

"Heat extremes can be very damaging to society and ecosystems, often causing heat-related deaths, forest fires or losses to agricultural production," Coumou said. "So an increase in frequency is likely to pose serious challenges to society and some regions will have to adapt to more frequent and more severe heat waves already in the near-term."