Fewer tornadoes are touching down in the United States, and we can thank global warming. This is the good news from researchers at the University of Illinois, who suggest that changes in atmospheric circulation linked to Arctic sea-ice retreat are the likely cause.
“A relationship between Arctic sea ice and tornadoes in the U.S. may seem unlikely,” said (Robert) Jeff Trapp, a professor of atmospheric sciences and co-author of the study. “But it is hard to ignore the mounting evidence in support of the connection.”
“Tornadoes and their parent thunderstorms are fueled by wind shear and moisture, when the jet stream migrates north, it takes the wind shear along for the ride, but not always the moisture. So, even though thunderstorms may still develop, they tend not to generate tornadoes because one of the essential ingredients for tornado formation is now missing.”
The reduced activity, the researchers believe, can be explained by how diminishing Arctic sea ice controls the path of the jet stream. As Arctic sea ice retreats, the jet stream migrates northward, and the atmospheric conditions that are favorable for tornado formation follow suit.
The researchers have analysed nearly three decades of weather and climate data, and found particularly strong correlations between tornado activity and the extent of Arctic sea ice, particularly during the month July.
Al Gore has directly linked increased numbers of tornadoes in particular years to climate change. Now it is clear that the trend has been for fewer tornadoes in the United States. In 2013, the tragic Oklahoma Tornado was followed by commentary implying that climate change may be to blame.
The new findings should help quell the hysteria surrounding the link between climate change and extreme weather events, and remind us that the consequences of a changing climate are not necessarily bad.
- Robert J. Trapp, Kimberly A. Hoogewind. Exploring a possible connection between U.S. tornado activity and Arctic sea ice. npj Climate and Atmospheric Science, 2018; 1 (1) DOI: 10.1038/s41612-018-0025-9
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August 6, 2018 at 12:56PM