Day By Day

Monday, November 21, 2005

PreIndustrial Climate Change

Back on the mountain -- cold and dreary (I'm referring to me, not the weather). "She Who Must Not Be Named” and I have come down with colds and are feeling dreary. We left the Harbor a day earlier than we had planned to and drove north, stopping from time to time to pick up necessities. Somehow feeling lousy takes all the fun out of grocery shopping. Tantalizing pastries and such hold no attraction at all for someone whose stomach is queasy. Consequently, we finished up at Whole Foods in only about fifteen minutes, and Wegmans took only a little longer. Then we were on our way into the wilds of Central Pennsylvania.

I hadn’t eaten anything all day so when we arrived on the mountain I snacked a bit and watched a nice little program on the History Channel on the subject of the “Little Ice Age” that afflicted the Northern Hemisphere from the Fourteenth through the Nineteenth Centuries. It followed three centuries of warmer times called the “Medieval Climatic Optimum.” This, of course, is old hat to professional historians and even to informed amateurs, but the general public, as well as many politicians encouraged by environmentalist activists, subscribes to the view that prior to the rise of industry earth’s climate was generally benign and stable. It’s nice to see reality being given at least some exposure, even if it is only on a cable channel.

As the show notes there is little scientific consensus regarding the reasons for the five century long cold snap. Three possibilities were mentioned:

1) a change in solar output [I remember a conversation I once had with Sallie Baliunas, the Harvard astronomer who specializes in Solar studies, where she expounded on the idea. At the time I found the idea that the Sun was a variable star very disquieting and said so. She just smiled. I suspect that most people, like me, shy away from the idea because it places our fates absolutely beyond our control.]

2) An unexplained upsurge in volcanism that blocked solar radiation from penetrating the atmosphere [this has been demonstrated in some specific cases in which unnaturally cold weather has followed upon documented eruptions, but it no more explicable or subject to human control than variations in Solar output and is therefore disheartening to contemplate]

3) The only comfortable perspective from which to view climatic fluctuations is the Anthropogenic hypothesis so much beloved by environmentalist activists. This argues that recent changes in the Earth’s climate are the result of human activity. This is comforting because it suggests that climate can at least to some extent be controlled. This perspective was introduced in the show only to explain the end of the cold snap. Presumably the rise of industry, by releasing greenhouse gasses into the atmosphere, brought the Little Ice Age to an end and restored the warmer temperatures of the Medieval Optimum. [As I remember Larry Niven and Steven Barnes did a novel on this subject some years ago.] Unmentioned was the suggestion, being explored by some scholars, of pre-industrial anthropogenic influences on climate. We now understand, for instance, that pre-Columbian Native American cultures engaged in extensive and quite destructive modification of local ecologies such as regular burning of woodlands, draining of wetlands, etc.

I missed the last half hour of the show, in part because I was getting really, really tired [colds have that effect on me] and because it seemed to be veering into a PC warning about the catastrophic effects of global warning, and as a consequence I was losing interest. One obvious point that was not discussed as such by the program, although I may have missed it at the end, was the distinct possibility that the global warming trend of the past century which has been well documented, might be both natural and beneficial.

One important point that did emerge from the show -- one that I want to emphasize:

Historians have a lot to contribute to current policy debates, even those carried on within the “scientific community,” if only someone is willing to listen to them. Both the Medieval Optimum and the Little Ice Age have long been known and their human and historical consequences understood by people in the field, although environmental “scientists” are just gradually becoming aware of them. More programs like this one that integrate historical and scientific perspectives would be useful.

I'm getting tired again -- back to bed.

Before I go, a brief word from Stephen Crane:

A man said to the universe:
"Sir I exist!"
"However," replied the universe,
"The fact has not created in me
A sense of obligation."
Somehow it seemed appropriate.

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