As winter takes hold in the Northern Hemisphere, we can count on many of those in denial about climate change to re-emerge after a summer of ignoring hot weather extremes to cite local cold weather as supposedly evidence against climate change. It is a Thinksee Nosebetter special, fully lacking any semblance of critical thinking - if it is "cold" somewhere, how can there be global warming?
It is worth pointing out first that "cold" is a relative and inexact term and that snow does not equal "cold". In many areas increases in heavy snowfall events are an expected consequence of global warming due to increased moisture in the air. And global warming does not mean there is no more winter or that everywhere always has sweltering heat going on. There will still be winter and cold, but in general averages will creep higher and warm extremes will become increasingly more common as cold extremes become less common.
Of course the main point I have made and will continue to make is that local and even regional cool spells over the course of weeks and even a season do not at all preclude a long-term worldwide shift toward a warmer climate. It is wrong to look at the relatively strong North Dakota economy of the past couple years and assume that the national and global economy must be fine too.
If you look around you can find plenty of individuals doing quite well in this down economy. Some, like a foreclosure specialist, may be doing well exactly because the overall economy is not doing well.
Similarly some of the current news-making cold outbreaks, particularly across Europe, may very well be due to global warming. This is the point where Thinksee Nosebetter tunes out and refuses to listen further because of a desire to believe that snow in England is not just a result of an unusual atmospheric circulation pattern but justifies denial of climate science.
It should be noted that at least for this past November in the non-tropical Northern Hemisphere besides northern Europe and part of western North America most other areas had above normal temperatures, and in many areas well above normal. What those maps of November temperature illustrate is that the hemisphere was warmer than normal overall because of the prevalence of warm anomalies. But some areas were under cooler temperature regimes basically because of a redistribution of air masses from the average configuration. The noted coldness across Europe is part of the other side of the coin of the extreme warmth in many other areas in the Northern Hemisphere.
For further more thorough explanation of the science behind the theorizing of how the warming world is helping drive cold winter weather in some areas I point to RealCimate. In short, the decreasing Arctic sea ice as a result of general warming may be driving circulation anomalies sending colder weather over some areas. Where there had been more sea ice and now there is less, more warmth is coming from the ocean into the atmosphere, and that warmth leads to rather persistent changes in the flow of air masses and weather patterns across a much larger area.
More simply, it is not as cold overall, but some of the cold has been shifted around to places that usually do not experience it.
There remains much to be learned about how and to what extent some people may experience cold spells systematically because of global warming. But certainly everyone will still at least occasionally experience cold weather due to random fluctuations in weather. Only the foolish and ignorant of climate science think those instances disprove that the climate is warming.
Sunday, December 19, 2010
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