As per a new study, the rapidly warming arctic is causing disruption in the jet stream leading to diminished summer storms which in turn is resulting in increased summer heat waves. The study has appeared in the journal Science. Lead-author Dim Coumou, of the Potsdam Institute for Climate Impact Research stated “When the great air streams in the sky above us get disturbed by climate change, this can have severe effects on the ground. While you might expect reduced storm activity to be something good, it turns out that this reduction leads to a greater persistence of weather systems in the Northern hemisphere mid-latitudes. In summer, storms transport moist and cool air from the oceans to the continents bringing relief after periods of oppressive heat. Slack periods, in contrast, make warm weather conditions endure, resulting in the buildup of heat and drought.”
Some highly controversial theories have surfaced since 2012 and the recent research is in favor of these theories. Potsdam researchers have stated that winter weather activity was the main focus of most of the previous researches on storm activity. Winter storm activity, which is the most damaging, is almost unchanged as per the global data; however, some regions may have unusual frequency or intensity of storms.
Analysis of weather station and satellite data suggests a prominent and consistent decline in average summer storm activity. This may lead to a decrease in frequency or intensity or both. The research team specifically analyzed synoptic eddies which is a specific type of turbulence and calculated the total energy held by them on the basis of their wind speed. The energy generated is a measure of the “interplay between intensity and frequency of high and low pressure systems in the atmosphere.” Since 1979, this intensity has dropped by ten percent. Co-author Jascha Lehmann said “Unabated climate change will probably further weaken summer circulation patterns which could thus aggravate the risk of heat waves. Remarkably, climate simulations for the next decades, the CMIP5, show the same link that we found in observations. So the warm temperature extremes we’ve experienced in recent years might be just a beginning.”
The Arctic is warming twice as fast as other regions of the Earth and this could be the driving force behind these changes. With the decline in sea ice coverage, less heat is absorbed by the region and the dark water reflects less light back into space. Usually the difference between the cold arctic and the warm air drives air movement. As this difference is less, the jet stream is weakened which is leading to decreased storm activity. Coumou explained “From whichever angle we look at the heat extremes, the evidence we find points in the same direction. The heat extremes do not just increase because we’re warming the planet, but because climate change disturbs airstreams that are important for shaping our weather. The reduced day-to-day variability that we observed makes weather more persistent, resulting in heat extremes on monthly timescales. So the risk of high-impact heat waves is likely to increase.”