Monday, December 21, 2009

Snow in Copenhagen

Tis the season for climate change skeptics to point out the unremarkable fact that it gets cold in the northern hemisphere this time of year. Media Matters has the roundup of the right wingers who seem to think it's clever to point out that it snowed in Copenhagen last week.
So perhaps I should go back to pointing out the difference between weather and climate.
Weather is what’s happening in a specific place at a specific time. Weather changes moment by moment. Climate encompasses the entire planet and changes slowly.
Given the considerable resistance among some to accepting the data on global warming, let's try another approach.
Imagine a large frozen object, such as a glacier or polar ice cap. When such an object remains roughly the same size over a long period of time, one could conclude that the temperature has remained in equilibrium. If such a large frozen object were to start shrinking, one could conclude with confidence that additional heat were being applied to said object.
So for those skeptics who question the charts depicting global temperatures rising after more than a thousand years of relative equilibrium, I would ask, what of the shrinking glaciers and ice caps?


Anonymous Edmund Dohnert said...

Tom -

I fully agree with you that many of the climate change skeptics either ignorantly or purposely confuse weather with climate. Having an unusually cold winter in one locale no more disproves global warming than does an unusually hot summer in another locale prove global warming. One must look at long-term trends.

As far as glaciers go, it is just a bit simplistic to compare a glacier to a big ice cube just sitting there melting away. In fact, they are extremely complex. Water is constantly being added to glaciers via snowfall and water is constantly being removed (via several different mechanisms). To further complicate the picture, glaciers are constantly moving, usually slowly oozing downhill toward the sea, where they break off to become icebergs.

The shrinkage of glaciers would indeed indicate that more water is being removed than added, and one can probably confidently infer that the reason is a combination of less snowfall and exposure of the periphery of the glacier to warmer air and water temperatures. But it is a further stretch to say that such phenomena is proof positive that the entire globe is warming, and ever a further stretch to infer an average global temperature for say the Fourteenth Century solely from glacier data.

Something is definitely going on here, but I think many of the climate change crowd would have us believe that they understand it with far more certainty than they really do.

5:54 PM, December 21, 2009  

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