Climatologists predict that extreme weather events will become more common as human-caused global warming intensifies. So I've been wondering if the really weird December weather here in the Pacific Northwest has anything to do with global warming.
There's a good chance that Portland will break the all-time record for least rainfall in December. I recall KGW meteorologist Rod HIll saying the record goes back all the way to 1876, or thereabouts.
New research presented at a recent American Geophysical Union meeting suggests there could be a link between the unusually long-lasting high pressure that has keep storms away from Oregon, and the loss of Arctic sea ice caused by global warming.
"The question is not whether sea ice loss is affecting the large-scale atmospheric circulation...it's how can it not?" That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk "Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?", presented at last week's American Geophysical Union meeting in San Francisco.
Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops. High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.
Now, so far there isn't conclusive evidence that this is happening, even though there's no doubt that the Arctic is getting warmer, greener, and with less ice.
But it sure seems reasonable to expect that losing Arctic sea ice equivalent to 44% of the size of the contiguous United States would, as Dr. Francis said, do something to the jet stream which normally funnels storms into the Pacific Northwest during the winter.
Here's another excerpt from the Climate Progress repost of Jeff Master's Wunderblog piece:
The Arctic has seen a stunning amount of sea ice loss in recent years, due to melting and unfavorable winds that have pushed large amounts of ice out of the region. Forty percent of the sea ice was missing in September 2007, compared to September of 1980. This is an area equivalent to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe. Such a large area of open water is bound to cause significant impacts on weather patterns, due to the huge amount of heat and moisture that escapes from the exposed ocean into the atmosphere over a multi-month period following the summer melt.