I Was On the Global Warming Gravy Train by David Evans

The political realm in turn fed money back into the scientific community. By the late 1990s, 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; there were international conferences full of such people. We had political support, the ear of government, big budgets. We felt fairly important and useful (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 above fell away. Using the same point numbers as above:

2) Better data shows that from 1940 to 1975 the earth cooled while atmospheric carbon increased. That 35 year non-correlation might eventually be explained by global dimming, only discovered in about 2003.

3) The temporal resolution of the ice core data improved. By 2004 we knew that in past warming events, the temperature increases generally started about 800 years before the rises in atmospheric carbon. Causality does not run in the direction I had assumed in 1999 — it runs the opposite way!

It took several hundred years of warming for the oceans to give off more of their carbon. This proves that there is a cause of global warming other than atmospheric carbon. And while it is possible that rising atmospheric carbon in these past warmings then went on to cause more warming ("amplification" of the initial warming), the ice core data neither proves nor disproves this hypothesis.

4) There is now a credible alternative suspect. In October 2006 Henrik Svensmark showed experimentally that cosmic rays cause cloud formation. Clouds have a net cooling effect, but for the last three decades there have been fewer clouds than normal because the sun's magnetic field, which shields us from cosmic rays, has been stronger than usual. So the earth heated up. It's too early to judge what fraction of global warming is caused by cosmic rays.

(Click to read entire article)