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Colder US Winters Due To Shifting Polar Jet Stream: Study
Brett Smith for redOrbit.com – Your Universe Online
Global warming skeptics have pointed to the unusually cold winter in parts of the United States this year as evidence against climate change.
However, a new study from Rutgers University indicates that the unusually chilly temperatures in the Midwest and southeastern US are consistent with projections of permanent shifts in weather patterns caused by rising temperatures.
According to the study, which was presented on Saturday at a meeting of the American Association for the Advancement of Science (AAAS) in Chicago, the high-altitude polar jet stream is slowing down and driving cold polar air to the south as a result.
The jet stream is created when cold Arctic air meets warmer air moving north from temperate latitudes and is driven by this temperature contrast. Study researcher Jennifer Francis, a climate expert at Rutgers, said the recent warming of Arctic air means there is now less of a difference in temperatures when polar air hits air from lower latitudes.
While the contiguous United States is currently going through an especially bitter winter, Alaska and other northern areas are currently going through an unusually warm winter.
This indicates “that weather patterns are changing,” Francis told the AFP. “We can expect more of the same and we can expect it to happen more frequently.”
Average Arctic temperatures have been rising “two to three times faster than the rest of the planet,” said James Overland, a weather expert with the National Oceanic and Atmospheric Administration (NOAA).
Francis said it may be too early to point the finger directly at human activities for this change.
“Our data to look at this effect is very short and so it is hard to get very clear signal,” she said. “But as we have more data I do think we will start to see the influence of climate change.”
Like most theories involving climate change, this shift in the activity of the jet stream is a controversial idea.
“There is evidence for and against it,” said Mark Serreze, director of the National Snowland Ice Data Center in Boulder, Colorado.
However, Serreze did admit that rising Arctic temperatures are linked to melting ice caps, which in turn leads to additional warming.
“The sea ice cover acts as a lid which separates the ocean from a colder atmosphere,” Serreze told the scientific conference. When that lid is removed, warmth contained in the water rises into the polar atmosphere.
“We are going to see changes in patterns of precipitation, of temperatures that might be linked to what is going on in the far north,” Serreze said.
Jerry Hatfield, head of the National Laboratory for Agriculture and Environment, warned that significant changes in weather affects many nations besides the United States.
“Look around the world — we produce the bulk of our crops around this mid-latitude area,” he said.
Agriculture is most affected by extreme weather patterns, which are largely driven by the activity of the jet stream.
Both droughts and freezes are already having “a major impact on animal productivity, it influences meat production, milk and eggs production,” Hatfield added.
Source: http://www.redorbit.com/news/science/1113072879/jet-stream-shift-causing-colder-winters-study-021714/
