My coldest winter since Chicago

Climate change is a politically charged subject. This makes it more difficult for us layman to evaluate the arguments over what is happening and expected to happen to temperatures (i.e. to know who to trust). “Climate change” is a more neutral term than “Global Warming” reflecting, I assume, the fact that scientists who specialize in climate and weather disagree not only over the impact of increases in CO2 on temperatures, but how to measure and compare temperatures over time. Should we measure land temperatures or sea temperatures or land and sea temperatures combined. Are these temperatures the result of averaging dozens or hundreds or tens of thousands of measurements and how is each reading weighed in the average? Which methods of measuring temperature are more reliable—satellite measures, ground stations, tree rings, etc. and how is one to be adjusted and matched to others in order to compare temperatures over long periods of time.

I suspect that one reason that global warming has been changed to climate change is that the global temperature has declined over the last 17 years. Temperatures have been rising and falling for thousands of years. By some measures (I have no idea which ones) it was hotter at the time of Christ than now and again in the 1300s AD and a lot hotter seven thousand years ago. But I don’t know how we can trust estimates of temperatures seven thousand years ago with now.

One of my favorite graphs is the “reconstructed global temperature over the past 420,000 years based on the Vostok ice core from the Antarctica (Petit et al. 2001).” The little red box on the far right is the most recent 5,000 years.

VostokTemp0-420000 BP

Thus I find the temperature information provided every morning in the Washington Post quite interesting. For example, yesterday at BWI the high was 23° and the low as 2°. The record high for BWI on the same date was 74° in 1930 (85 years ago) and yesterday’s low was the record low for that date. Fifty or so miles south at Reagan National (don’t quote me on the distance) the high yesterday was 27° and the low was 14° (well it is further south) while the record high and low for that date were 75° in 1953 and 7° in 1885. If those constitute a trend we must be moving into another ice age. Though it feels like it, I doubt it. Climate change seems the right words to describe what we have observed.