Global warming and other forms of climate change are driving unusual weather patterns around the globe. These conditions may be driven, at least in part, by changes in the jet stream, high-altitude winds that carry many weather patterns around the world.
Some researchers believe that melting in polar ice caps and other changes in the climate could be responsible for extreme weather conditions, including the severe winter seen along the east coast of the United States this year that brought record-breaking snowfalls to cities like Boston.
New research from the Potsdam Institute for Climate Impact Research and the University of Potsdam suggests that climate change is altering the jet stream. This could result not only in more severe winters, but in higher temperatures during the summer as well, climatologists warn.
Polar regions of the Earth are warming faster than areas near the equator, reducing the difference in temperatures between upper and lower latitudes. This effect has reduced winds circling areas of high and low pressure systems, known as eddy kinetic energy (EKE). These conditions are resulting in more persistent weather that changes more slowly than normal, potentially driving heat waves that last longer than normal.
"That's why they're saying that it's more likely to have summer extreme events. Because the weather just is not changing as much, and the weather systems themselves are just more stagnant and lethargic," Jennifer Francis of Rutgers University said.
A heat wave in Russia during 2010 drove temperatures as much as 18 degrees above normal, resulting in the deaths of as many as 55,000 people. The eddy kinetic energy seen in air pressure systems over Moscow that year was extremely low. This suggests that there may not have been enough energy to carry cooling temperatures over the nation, causing the heat wave.
Rising global temperatures could be resulting in a greater amount of thermal energy being released to the atmosphere from polar regions. This additional energy could be reducing EKE, weakening the jet stream, bringing longer heat waves to temperate regions, as well as extreme winter conditions.
Summer storms often bring wetter, cooler conditions to regions, breaking up potentially dangerous heat waves. However, a weakening EKE could be result in fewer storms during summer months, increasing the effect of such weather conditions.
As global temperatures continue to rise, heat waves could become stalled over areas more often, increasing the damage they can cause.
"It is increasingly clear that global warming does not just mean global warming in a narrow sense. Our planet is not simply getting warmer - rather this warming comes with real changes to the workings of the atmosphere and the oceans," Stefan Rahmstorf, a climatologist at the Potsdam Institute for Climate Impact Research, said.
Analysis of the effect of reduced eddy kinetic energies on weather systems was detailed in the journal Science.