It happened again.

Someplace attained a record, unseasonable cold temperature, so my favorite wingnut sent me a link to the story with a snide comment about “Global warming, huh?” This happens every time there is an unusual snowfall or late frost or whatever.

Now, the fact of the matter is, every one of these incidents can be seen as further evidence for the global-warming model. As the earth absorbs heat, it does so very unevenly. There are certain hotspots that warm up more quickly, and other cold spots that take on heat more slowly. The result is that there is more total heat energy in the system, and the atmosphere of the earth functions like one large and very complex heat engine that becomes wilder and more unpredictable in its actions as more energy pours into the system.

Yes, overall, the temperature is going up (very rapidly on a geological scale, but apparently much more slowly on a human scale). But what is increasing much more rapidly than the mean temperature is the total craziness in the weather machinery. More energy, absorbed very unevenly at various points on the globe, means greater turbulent variation in high and low-pressure systems, dramatic and unpredictable shifts in ocean currents, and a general increase in events that are outside the norm.

Put in statistical terms, the variance is increasing much more rapidly than the mean. The net result is that the wild swings in the weather are much more dramatic than are the comparatively small, but cumulatively disastrous, upward trends in temperature. We observe a set of record low temperatures in some locations that seem to cancel out the string of record high temperatures that are occurring elsewhere. But when we attend merely to the individual temperatures, we are missing the main point, which is that we are seeing unprecedented extremes in the weather, and it is these extremes--both high and low--that are the signature of global warming.