Be it heavy downpours or super-hot spells, summer weather becomes more persistent in North America, Europe and parts of Asia. When those conditions stall for several days or weeks, they can turn into extremes: heatwaves resulting in droughts, health risks and wildfires; or relentless rainfall resulting in floods. A team of scientists now presents the first comprehensive review of research on summer weather stalling focusing on the influence of the disproportionally strong warming of the Arctic as caused by greenhouse-gas emissions from burning fossil fuels. Evidence is mounting, they show, that we likely meddle with circulation patterns high up in the sky. These are affecting, in turn, regional and local weather patterns – with sometimes disastrous effects on the ground. This has been the case with the 2016 wildfire in Canada, another team of scientists show in a second study. “Giant airstreams encircle our globe in the upper troposphere – we call them planetary waves,” explains Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research (PIK) and co-author of the second paper. “Now evidence is mounting that humanity is messing with these enormous winds. Fueled by human-made greenhouse-gas emissions, global warming is probably distorting the natural patterns.
From Potsdam Institute Photo John Vlahakis