From: Fred Pearce, Yale Environment360
Published March 1, 2014 07:59 AM

Is Global Warming responsible for weather extremes?

Scientists are trying to understand if the unusual weather in the Northern Hemisphere this winter — from record heat in Alaska to unprecedented flooding in Britain — is linked to climate change. One thing seems clear: Shifts in the jet stream play a key role and could become even more disruptive as the world warms.

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This winter's weather has been weird across much of the Northern Hemisphere. Record storms in Europe; record drought in California; record heat in parts of the Arctic, including Alaska and parts of Scandinavia; but record freezes too, as polar air blew south over Canada and the U.S., causing near-record ice cover on the Great Lakes, sending the mercury as low as minus 50 degrees Celsius in Minnesota, and bringing sharp chills to Texas.

Everyone is blaming the jet stream, which drives most weather in mid-latitudes. That would be a significant development. 

The polar jet stream may be driving a "hemispheric pattern of severe weather."
to the jet stream in the coming decades looks likely to be the key link between the abstractions of climate change and real weather we all experience. So, is our recent strange weather a sign of things to come? Are we, as British opposition leader Ed Milliband put it this month while surveying a flooded nation, "sleepwalking to a climate crisis"?

The story gets tangled because trying to identify long-term trends amid the noise of daily weather is hard.

The U.K. Met Office, which keeps a global weather watch, said in a rush report put out in mid-February that we are experiencing a "hemispheric pattern of severe weather," and that the events are linked. The most extreme days of the U.S. cold event, for instance, coincided with some of the most intense storms over the U.K. And physically the connection is through the polar jet stream, which the report said showed a "persistent pattern of perturbations" — in other words, it ran wild.

Jet Stream image via NASA Godard Space Flight Center

Read more at Yale Environment360.

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