Backseat Driving (Brian Schmidt): A climate skeptic's guest post: Why David Evans bet against Brian Schmidt over global warming. Interesting post by David Evans who worked for a few years in climate modeling.
I devoted six years to carbon accounting, building models for the Australian government to estimate carbon emissions from land use change and forestry (Google on "FullCAM"). When I started that job in 1999 the evidence that carbon emissions caused global warming seemed pretty conclusive, but since then new evidence has weakened the case that carbon emissions are the main cause. I am now skeptical. As Lord Keynes famously said, "When the facts change, I change my mind. What do you do, sir?"
In the late 1990's the evidence suggesting that carbon emissions caused global warming was basically:
1. Carbon dioxide is a greenhouse gas. Proved in a laboratory a century ago.
2. Global warming has been occurring for a century, especially since 1975, and concentrations of atmospheric carbon have been rising for a century, especially since 1975. Correlation is not causation, but in a rough sense it looked like a fit.
3. Ice core data, starting with the first cores from Vostok in 1985, allowed us to measure temperature and atmospheric carbon going back hundreds of thousands of years, through several dramatic global warming and cooling events. To the temporal resolution then available (data points were generally more than a thousand years apart), atmospheric carbon and temperature moved in lock-step: there was an extremely high correlation, they rose and fell together. Talk about a smoking gun!
4. There weren't any other credible suspects for causing global warming. So presumably it had to be carbon emissions.
This evidence was good enough: not conclusive, but why wait until we are absolutely certain when we apparently need to act now? So the idea that carbon emissions were causing global warming passed from the scientific community into the political realm, and actions started to happen. Research increased, bureaucracies were formed, international committees met, and eventually the Kyoto protocol was signed in 1997 — with the aim of curbing carbon emissions.
And the political realm in turn fed money back into the scientific community. By the late 1990's, lots of jobs depended on the idea that carbon emissions caused global warming. Many of them were bureaucratic, but there were a lot of science jobs created too. I was on that gravy train, making a high wage in a science job that would not have existed if we didn't believe carbon emissions caused global warming. And so were lots of people around me; and there were international conferences full of such people. And we had political support, the ear of government, big budgets, and we felt fairly important and useful (well, I did anyway). It was great. We were working to save the planet!
But starting in about 2000, the last three of the four pieces of evidence outlined above fell away or reversed. Using the same point numbers as above: …
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