by Nathaniel Smith, Politics: A View from West Chester, 3/3/14
The current pattern, here in Pennsylvania, of unusually hot summers and unusually cold winters, is surprising us all. But it shouldn’t, as it has been going on for several years.
We tend to think our own weather sets the worldwide trend. The forecast for tonight in West Chester is for -1 degrees. How about Anchorage, Alaska? A balmy 21 degrees! That extremely random sample bears out the premise of what you are about to read.
I’m going to repost what I still see as the reasonable explanation for the climatic weirdness of our time, from a blog I wrote three years ago, “Why it’s colder here—because it’s warmer there,” in February 2011:
I just heard an interesting interview by Robin Young, “Scientists Blame Dramatic Weather On Weakening ‘Arctic Fence,’” Here and Now, 2/3/11. Listen there; here’s the online description:
Many parts of Europe and the U.S. have seen unusual snowstorms and frigid temperatures for two years in a row. But places like northern Canada and Greenland have seen temperatures that in some months are running 15 to 20 degrees above average.
The reason, some researchers say, is a weakening “vortex,” a kind of atmospheric fence, that normally keeps cold air up north and warmer air south. We speak with Justin Gillis, who covers climate issues for the New York Times, about why the weather world seems to have flipped upside down.
The interview brings out that the jet stream, which normally circles the North Pole from west to east, currently is dipping down to visit us, one factor in the disrupted weather patterns the world has seen lately.
People tend to have short memories. Many of us have probably stepped outside the last few weeks and exclaimed: “Well, global warming is over, at least!”
Not likely: the program mentioned that 2010 tied 2005 and 1998 as the warmest ever as a global average and 2010 saw the hottest summer ever in the Mid-Atlantic states. The globe has warmed by 1.4 degrees Fahrenheit in the last couple of centuries, most in the past 30 or 40 years, according to Justin Gillis. See his related New York Times article “Cold Jumps Arctic ‘Fence,’ Stoking Winter’s Fury.”
In sum, it seems quite likely that the weather is (somewhat) colder than usual here right now because it’s (a lot) warmer in the Arctic.
Find out more in “A ‘Bulge’ in Atmospheric Pressure Gives Us a Super-Cold Winter Amid Global Warming” by Christa Marshall and Tiffany Stecker, New York Times, 1/5/11:
…According to some climate scientists, the cold in places like Florida actually could be a sign of warming, rather than an argument against the phenomenon.
The ongoing disappearance of sea ice in the Arctic from elevated temperatures is a factor to changes in atmospheric pressure that control jet streams of air, explained James Overland, an oceanographer of the National Oceanic and Atmospheric Administration, or NOAA.
That is because ice-less ocean is darker and, thus, absorbs more solar heat, which in turn spews warmer air than average back into the Arctic atmosphere.
That unusually warm air can contribute to a “bulge” effect to the atmospheric pressure controlling how cold air flows, according to Overland, who works at NOAA’s Pacific Marine Environmental Laboratory. Rather than moving circularly in the Arctic from west to east as typical, the bulge may prompt air to move in a U-shaped pattern down to the southern United States….