Climate change is causing major planetary atmospheric circulation systems like the jet stream to slow down — stalling summer weather patterns across Europe, North America, and parts of Asia, according to a new analysis published in the journal Nature Communications. As a result, rains are turning into floods, sunny days into long-lasting heat waves, and dry conditions into wildfires.
“While it might not sound so bad to have more prolonged sunny episodes in summer, this is in fact a major climate risk,” the scientists, led by Dim Coumou of the Potsdam Institute for Climate Impact Research (PIK), said in a statement. “We have rising temperatures due to human-caused global warming, which intensifies heat waves and heavy rainfall, and on top of that we could get dynamical changes that make weather extremes even stronger – this is quite worrying.”
In the coming decades, this disruption of global atmospheric circulation systems could cause “very extreme extremes,” particularly in major agricultural regions, the study concludes.
In the Northern hemisphere, the difference in temperature between the Arctic and the Equator has historically been the driving force behind the air streams that shift weather patterns eastward across continents. But the Arctic has been warming two to four times faster than the rest of the globe, causing this temperature gap to narrow. As The Guardian’s Jonathan Watts explains, “as this ramp flattens, winds struggle to build up sufficient energy and speed to push around pressure systems in the area between them.”
A prime example of this phenomenon is Hurricane Harvey, which hovered over Texas’ coastline for an unusually long time last summer, which allowed the storm to continuously refuel itself using warm Gulf of Mexico waters and drop record-breaking levels of rain.
Western Canada’s recent string of intense, prolonged wildfires — such as a two-month wildfire in Alberta in 2016 that caused $3.6 billion in damages — is another example of stalled weather patterns, finds a second study published by the same team of scientists in the journal Scientific Reports.