Jet Stream Changes due to Global Warming?

Posted by Joshua S. Hill

April 22, 2008

In an article that just screams northern-hemispheric superiority, MSNBC has touched only briefly upon new research from scientists at the Carnegie Institute.

According to Cristina Archer and Ken Caldeira of the Carnegie Institution’s Department of Global Ecology, Earth’s jet streams are shifting; possibly as a result of global warming. However they are upfront with the fact that they need to do more research before they can pinpoint what will happen, and why it is happening.

Jet streams are the high-altitude bands of fast moving wind that influence the paths of storms and other weather systems. “The jet streams are the driving factor for weather in half of the globe,” says Archer. “So, as you can imagine, changes in the jets have the potential to affect large populations and major climate systems.”

The Carnegie pair studied research taken over a 23 year span from 1979 to 2001, consisting of changes in the average position and strength of the planets jet streams. The data came from the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Protection, and the National Center for Atmospheric Research, and included outputs from weather prediction models, conventional observations from weather balloons and surface instruments, and remote observations from satellites.

MSNBC focused upon evidence that the jet stream in the northern hemisphere – what they label “America’s stormy weather maker” – is moving northward and weakening in intensity. What that means for the US is less rain in the already dry South and Southwest of the country, and an increase in storms in the north.

Jet streams have another impact upon the weather systems, that of suppressing the development of hurricanes. With the US jet stream dissipating and moving north, Archer and Caldeira suspect that the number of hurricanes could increase, and the strength grow.

Consider this analogy; a part of town with a medium crime rate already has large police protection. But imagine if that police protection decided to move away. With whatever was keeping that crime rate down moving away, the crime rate would increase. The same can be said for hurricanes, with the jet streams moving away from the sub-tropical zones where hurricanes are born.

The changes to Earth’s jet stream’s is consistent with numerous other signals of global warming. Those other signals include the widening of the tropical belt, the cooling of the stratosphere and the poleward shift of storm tracks. However this is the first study to use observation-based datasets to examine these trends in the jet streams.

“At this point we can’t say for sure that this is the result of global warming, but I think it is,” says Caldeira. “I would bet that the trend in the jet streams’ positions will continue. It is something I’d put my money on.”

Photo Courtesy of Space Ritual via Flickr

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