Summer weather is stalling, leading to more extremes

New peer-reviewed research from the Potsdam Institute for Climate Impact Research shows that there is mounting evidence that humans are influencing the giant airstreams that circle the globe high above the surface and steer weather systems.

A blocked up (nearly stalled) North Atlantic weather pattern. Image courtesy NOAA.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x390_08221751_art2fig12.jpg"/>

Key excerpts from the <a href="https://www.pik-potsdam.de/news/press-releases/nice-sunny-days-can-grow-into-heat-waves-2013-and-wildfires-summer-weather-is-stalling">Potsdam Institute for Climate Impact Research.....</a>
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Under global warming, the Arctic warms more than the rest of the Northern Hemisphere. This reduces the temperature difference between the North Pole and the equator, yet this very difference is a main driving force for the airstreams. “There are many studies now, and they point to a number of factors that could contribute to increased airstream stalling in the mid-latitudes – besides Arctic warming, there’s also the possibility of climate-change-induced shifting of the storm tracks, as well as changes in the tropical monsoons,” says Simon Wang from Utah State University in the United States, a co-author of the review paper.</em>

When weather systems slow down elements such as rainfall can be more intense and persist for a longer duration, increasing the risk of dangerous floods. High pressure systems that stall out can lead to long periods of sunny, dry weather, which can quickly turn into a serious drought. They can also lead to longer, more intense heat waves. One example of this was the outbreak of massive wildfires that we saw in western Canada back in 2016 due to the extended period of unusually warm and dry weather.

<em>“There is strong evidence that winds associated with summer weather systems are weakening and this can interact with so-called amplified quasi-stationary waves. These combined effects point towards more persistent weather patterns, and hence more extreme weather," said Wang.</em>

The research team noted that these observed changes are typically more pronounced than what the climate models project.

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This study was recently published in the journal Nature Communications.