He says, "since 1999 new evidence has seriously weakened the case that carbon emissions are the main cause of global warming, and by 2007 the evidence was pretty conclusive that carbon played only a minor role and was not the main cause of the recent global warming. As Lord Keynes famously said, 'When the facts change, I change my mind. What do you do, sir?'"
The reasons for his change of mind:
- "The greenhouse signature is missing. We have been looking and measuring for years, and cannot find it." The signature of an increased greenhouse effect is a hot spot about 10 km altitude in the atmosphere over the tropics. In 2007, the evidence was conclusive that no such hot spot exists, though hundreds of measurements have been made looking for it.
- There is no evidence to support the hypothesis that carbon dioxide emissions cause significant global warming.
- The satellites that measure the world's temperature say warming ended in 2001. The temperature has since dropped, so that it has returned to that of 1980. Land-based temperature readings are corrupted by the urban heat island effect and cannot be trusted. Only the satellite data is trustworthy and it only goes back to 1979.
- "The new ice cores show that in the past six global warmings over the past half million years, the temperature rises occurred on average 800 years before the accompanying rise in atmospheric carbon. Which says something important about which was cause and which was effect."
Evans says that the debate on global warming has "consisted of a simple sleigh of hand: show evidence of global warming, and while the audience is stunned at the implications, simply assert that it is due to carbon emissions. In the minds of the audience, the evidence that global warming has occurred becomes conflated with the alleged cause, and the audience hasn't noticed that the cause was merely asserted, not proved. If there really was any evidence that carbon emissions caused global warming, don't you think we would have heard all about it ad nauseam by now? The world has spent $50 billion on global warming since 1990, and we have not found any actual evidence that carbon emissions cause global warming. Evidence consists of observations made by someone at some time that supports the idea that carbon emissions cause global warming. Computer models and theoretical calculations are not evidence, they are just theory."
I would add to this that the computer models have had a consistent record of predicting larger temperature increases than have actually occurred, even prior to the totally unexplainable recent decrease in temperatures. That is, unexplainable in terms of the carbon emissions computer models. They are more understandable in terms of such things as variations in the solar radiation reaching Earth and other natural phenomena. Indeed, there is a huge hubris at work when people make overblown predictions of man-made global warming being dominant over natural causes when we look at the record of the Earth's temperature over the last 600 million years. In that record, the present temperatures are very unusually low and the carbon dioxide concentrations in the atmosphere are also very low. It is foolish to put much truck in these computer models which are totally unable to predict the past in accordance with the known record.
It is shameful that so many scientists are unable to reason this out. Of course many of them are on university campuses where science is often held hostage to socialism and anti-capitalist causes. When campus politics comes to play a role, objectivity vanishes. Some others work for government agencies, which are commonly eager to expand their powers in a war against some threat or other, which they are often happy to exaggerate or manufacture.