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Interviewee: Cristina Archer,
Rivers of Air
Somewhere above us churn rivers of air, speeding along at anywhere from 60 to 250 miles an hour: the jet streams. These meandering rivers loop north and south at elevations of eight to 12 miles and are what drive our weather. In the mid latitudes, such as over the United States, they flow west to east, shoving highs and lows, cold fronts and warm fronts, from the Pacific to the Atlantic. But scientists have found the overall location is gradually changing. Cristina Archer of the Carnegie Institution of Washington at Stanford says, “The jets (jet streams) have been moving towards the poles, both in the northern and southern hemisphere.”
She and co-author Ken Calderia, also with the Carnegie Institution combed 23 years of records to find that, on average, the jet streams are shifting at the rate of 1.25 miles a year, something they believe is connected to global warming. Archer says they were not surprised by the discovery, noting that other studies have found that the atmosphere in the subtropical regions near the equator is heating up and expanding. As the tropical air region expands, Archer notes, “The jet streams are pushed towards… the poles as well.”
Archer adds that means weather patterns will also shift. She says, “Changes to the jets mean changes to the storms, and changes to the storms means changes in precipitation, changes in how much rain and how much snow we can count on.”
Their research also showed that the jet streams are gaining altitude. But, the changes are not the same everywhere. She notes that the jet stream shift “over Asia is much stronger than the shifts over North America.”
While the shift is small, only a little more than six yards a day, Archer says, “If there was a big shift, that would mean big trouble for us.” Large shifts would steer storms in a far different pattern, resulting in extreme changes in climate.
But even a gradual change is significant. She notes that over time, it could pose a problem for some plants and animals that can’t adapt that quickly.
While the study did not focus on hurricanes, there is the possibility that a shift in the jet streams away from where hurricanes develop might mean more hurricanes. For a hurricane to develop a number of factors must be just right, including a lack of wind in the area where the hurricane is developing. Therefore, Archer notes that the presences of a jet stream means “the hurricanes cannot form as strongly as they could,” and vice-versa. However, Archer cautions to not draw too strong of a conclusion about the future of hurricanes, noting that, “There are other effects of global warming on hurricanes that we did not look at and that cannot be dismissed.”
The study was published in the journal “Geophysical Research Letters,” on April 18, 2008, and was funded by the University of Calgary.
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