Many people write sensible things about anthropogenic global warming, but I find Professor William Happer's statement to the US Senate on February 25, 2009, especially clear and convincing .
Happer is the Cyrus Fogg Bracket Professor of Physics at Princeton University. He was also the Director of Energy Research at DOE from 1990-93, where he supervised all of DOE's work on climate change. He says this:
"The climate is warming and CO2 is increasing. Doesn't this prove that CO2 is causing global warming through the greenhouse effect? No, the current warming period began about 1800 at the end of the little ice age, long before there was an appreciable increase of CO2. There have been similar and even larger warmings several times in the 10,000 years since the end of the last ice age. These earlier warmings clearly had nothing to do with the combustion of fossil fuels. The current warming also seems to be due mostly to natural causes, not to increasing levels of carbon dioxide. Over the past ten years there has been no global warming, and in fact a slight cooling. This is not at all what was predicted by the IPCC models."
He explains the "bit player" role that CO2 plays in greenhouse warming. Even if doubled, CO2 in the atmosphere would increase global temperatures "on the order of one degree," all else equal, and that would be about as much as it could ever increase it.
He explains that not all else is equal. He explains that satellite measurements indicate that water vapor and clouds, which account for 90% of greenhouse warming, have a negative feedback with CO2 levels, thus counteracting most or all of the warming effects of CO2.
He explains that temperatures have been warmer in the past and undergo cycles, counter to the "hockey stick" graph trumpeted in the third report of the IPCC. The hockey stick
"was the result of incorrect handling of proxy temperature records and incorrect statistical analysis. There really was a little ice age and there really was a medieval warm period that was as warm or warmer than today. I bring up the hockey stick as a particularly clear example that the IPCC summaries for policy makers are not dispassionate statements of the facts of climate change."
He explains how ice core observations show that historical temperatures and CO2 levels are indeed correlated, but that temperature increases preceded the CO2 increases - by "about 800 years", thus indicating that warming causes increased CO2 and not vice versa.
He explains how erroneous computer models are.
"It is true that climate models use increasingly capable and increasingly expensive computers. But their predictions have not been very good. For example, none of them predicted the lack of warming that we have experienced during the past ten years. All the models assume the water feedback is positive, while satellite observations suggest that the feedback is zero or negative."
On sea level rise,
"The sea level is indeed rising, just as it has for the past 20,000 years since the end of the last ice age. Fairly accurate measurements of sea level have been available since about 1800. These measurements show no sign of any acceleration."
He explains that CO2, and higher concentrations of it in the atmosphere, are actually good for us. "Crop yields will continue to increase as CO2 levels go up... moderate warming is an overall benefit to mankind because of higher agricultural yields and many other reasons."
And finally, he shoots down the supposed "scientific consensus" on global warming. For one, consensus is not the way science works. And two, there is no consensus.
His statement is truly scientific. Not because he is a credentialed scientist, but because he uses physical observations to support or falsify hypotheses. Unlike so many other statements on climate change (e.g., any statement from Al Gore or NASA's James Hansen), you can follow his reasoning and it makes sense.
Keep his testimony in your hip pocket, for the next time you are called a "denier."