Extreme winter weather isn’t down to a wavier jet stream

According to new research, the increasingly erratic winter times in the northern hemisphere are not the result of the fleeing flow of becoming more wavy – although climate change makes winter storms more intense in other respects.

The northern polar jet flow is a current of winds that sweeps away the northern hemisphere, directed by the limits between temperate air and cold air around the Arctic.

For more than a decade, some researchers suspect that warming the Arctic causes a more dramatic jet jet loop in winter, causing extreme storms that bring snow and ice much more south than usual.

But the theory was difficult to verify, partly due to the recording of relatively short satellite data, and also because of the intense natural variability of the jet flow during the winter months.

Erich Osterberg at Dartmouth College, New Hampshire, and his colleagues have decided to determine whether the recent Jet Stream behavior is out of the ordinary compared to the long -term average.

The satellites began to collect reaction flow data in 1979, so that the researchers used data on temperature and atmospheric pressure extending to 1901 to rebuild the movement of the polar jet on the United States for the rest of the 20th century.

They found that the polar jet had experienced several increased ripples during this period, suggesting that the recent erratic behavior is not out of the ordinary. In some cases, the winter jet flow was even more vague in the past than today. “What is going on now with the Jet Stream does not seem really unusual when you zoom in and look all the 20th century,” explains Osterberg.

The winters of the northern hemisphere are becoming hotter and warmer due to climate change causing more intense storms and precipitation, even without the change of jet, underlines Osterberg. “It is clear that climate change affects extreme weather events in all kinds of really important ways,” he said. “What we say is that, as far as the winter jet flow is concerned, it does not seem that the jet flow is an essential element of these changes.”

Tim Woollings at the University of Oxford says that research recalls how important it is to assess long -term data when identifying modifications to the fleeing flow, the behavior of which can vary enormously in the short and medium term. “Using several long data records and a range of methods, it shows how jets in recent North American winters is not worse than in previous decades,” he said.

This is another story during the northern hemisphere, however, with growing evidence suggesting that the polar jet becomes more wavy during the hottest months due to climate change which increases air temperatures under the tropics. “In summer, it seems that the Jet Stream sees a fundamental change in behavior, where it becomes slower, with larger waves, which leads to things like big waves of heat, drought and forest fires,” explains Osterberg. “It seems to be associated with climate change.”