Global Dimming
Industry Figures John Blackburn and Curt Welch alerted me to this issue over a year ago. I’m not sure why I didn’t post something about it at the time — probably because it left me badly taken aback.
I just tonight saw the BBC Horizon episode whose transcript is referenced here, which Curt originally pointed out, and which was recently shown, in a slightly different form, as “Dimming the Sun”, on Nova.
I found it disturbing as hell: Global Dimming, another new widespread global climate change, is troubling enough on its own, but it has likely also masked the true extent of Global Warming, meaning that the fundamental warming trend is actually much (much) larger than previously imagined.
NARRATOR: September 12th 2001, the aftermath of tragedy. While America mourned, the weather all over the country was unusually fine. Eight hundred miles west of New York, in Madison, Wisconsin a climate scientist called David Travis was on his way to work.
DR DAVID TRAVIS (University of Wisconsin, Whitewater): Around the twelfth, later on in the day, when I was driving to work, and I noticed how bright blue and clear the sky was. And at first I didn’t think about it, then I realised the sky was unusually clear.
NARRATOR: For 15 years Travis had been researching an apparently obscure topic, whether the vapour trails left by aircraft were having a significant effect on the climate. In the aftermath of 9/11 the entire US fleet was grounded, and Travis finally had a chance to find out.
DR DAVID TRAVIS: It was certainly, you know, one of the tiny positives that may have come out of this, an opportunity to do research that hopefully will never happen again.
NARRATOR: Travis suspected the grounding might make a small but detectable change to the climate. But what he observed was both immediate and dramatic.
DR DAVID TRAVIS: We found that the change in temperature range during those three days was just over one degrees C. And you have to realise that from a layman’s perspective that doesn’t sound like much, but from a climate perspective that is huge.
NARRATOR: One degree in just three days — no one had ever seen such a big climatic change happen so fast. This was a new kind of climate change. Scientists call it Global Dimming…
Read the Full Transcript from the BBC.
There is also a Wikipedia Entry, of course, but the BBC transcript is more extensive (and dramatic).
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