Jet stream, America’s storm maker, moving slowly northward

The jet stream — America’s stormy weather maker — is creeping northward and weakening, new research shows. That potentially means less rain in the already dry South and Southwest and more storms in the North.

From 1979 to 2001, the Northern Hemisphere’s jet stream moved northward on average at a rate of about 1.25 miles a year, according to the paper published Friday in the journal Geophysical Research Letters. The authors suspect global warming is the cause, but have yet to prove it.
The study looked at the average location of the constantly moving jet stream and found that when looked at over decades, it has shifted northward. The study’s authors and other scientists suggest that the widening of the Earth’s tropical belt — a development documented last year — is pushing the three jet streams toward the poles.

Climate models have long predicted that with global warming, the world’s jet streams would move that way, so it makes sense to think that’s what happening, Caldeira said. However, proving it is a rigorous process, using complex computer models to factor in all sorts of possibilities. That has not been done yet.

A rate of 1.25 miles a year “doesn’t sound like much, but that works out to about 18 feet per day,” Caldeira said. “If you think about climate zones shifting northward at this rate, you can imagine squirrels keeping up. But what are oak trees going to do?

“We are seeing a general northward shift of all sorts of phenomena in the Northern Hemisphere occurring at rates that are faster than what ecosystems can keep up with,” he said.

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