I’m most grateful to Justin Pulliam for having been so thoughtful and helpful a guide during the East Coast leg of my current speaking tour of the US and Canada. For once the environmentalist faction stumbled into a real debate, and I am most grateful to Anthony Watts for putting this revealing account of it on the record in his influential blog, which now carries more weight than most “mainstream” news media, and a great deal more information.
Some commenters have had difficulty in getting access to the video of my lecture at Union College. Professor Larry Gould of Hartford University, with his characteristic thoroughness, has posted up the fuller version of the lecture that I had the honor to give at his university in the presence of its president, Walter Harrison. Larry has helpfully included all the slides in the right places. The link is:
One commenter has asked why, since I oppose the notion of doing science by consensus, I said in my talk that it was “generally accepted” that 1.2 Kelvin of global warming will be likely to occur in response to a doubling of atmospheric CO2 concentration, where there are no feedbacks or the feedbacks are net-zero.
The relevant slide shows how the IPCC calculates this 1.2 K. One multiplies the IPCC’s radiative forcing from a doubling of CO2 (5.35 ln 2 = 3.71 W/m2: Myhre et al., 1998) by the Planck climate-sensitivity parameter (0.31 K/W/m2: IPCC, 2007, p. 631 fn.), and increases the result by approximately one-sixth to allow for latitudinal variations in temperature at the characteristic-emission altitude. It is worth noting that neither of the two relevant quantities can be measured directly. Both are guesses, and both may be exaggerations.
Professor Chris Essex of the University of Western Ontario performed some of the earliest spectral-line-by-spectral-line calculations to determine the form of the CO2 radiative forcing. Though he is willing to confirm that the the equation is indeed logarithmic, so that each additional molecule of CO2 has less forcing effect than its predecessors, he is less sure about the coefficient, which the IPCC has already reduced by 15% (it was 6.3 in the 1990 and 1995 reports). The coefficient, and hence the CO2 radiative forcing, may still be too high, and perhaps substantially so.
There is also doubt about the value of the Planck climate-sensitivity parameter, which also cannot be measured but is crucial because not only the original warming caused by CO2 before feedbacks but also, separately, the feedbacks themselves are dependent upon it. The Moon, which has no atmosphere, is a helpful benchmark, because the mean surface temperature is also the emission temperature. Theory (see NASA’s lunar fact-sheet, for instance) gives 271 K as the mean lunar surface temperature. However, the Diviner mission has established that at the lunar equator, the warmest part of the surface, the mean temperature is just 206 K. This implies that the mean temperature of the entire lunar surface is 193-194 K, a long way below the 271 K given by the use of the Stefan-Boltzmann equation (assuming albedo 0.11 and emissivity 1). If the Earth’s true emission temperature (which occurs somewhere at altitude in the troposphere) is less than the 255 K predicted by theory (assuming an albedo 0.306), then the Planck parameter may well be considerably less than the IPCC’s value, in which event on this ground alone climate sensitivity may be well below its central estimate of 3.26 K per CO2 doubling.
For the sake of brevity, I took the “official” values of the CO2 radiative forcing and of the Planck parameter as correct, and pointed out to the audience that the major debate between the skeptics and the believers centers on the overall feedback gain factor, which – in the IPCC’s implicit central estimate – is 2.81, almost tripling the warming that a CO2 doubling causes before feedbacks are taken into account. It is not possible to measure any individual temperature feedback directly, so the feedback multiplier is based on a (probably exaggerated) guess as to the value of the Planck parameter and (near-certainly very much exaggerated) guesses as to the values of the various temperature feedbacks.
My best estimates (guesses, but perhaps better guesses than those of the IPCC because I have no vested interest in the answers) are that the IPCC exaggerates the CO2 radiative forcing (which cannot be measured) by around 20%; that it exaggerates the Planck parameter (which cannot be measured) by 20%; and that it exaggerates the sum of all unamplified feedbacks (which cannot be measured) threefold, because, as Lindzen and Choi (2009,, 2011) and Spencer and Braswell (2010, 2011) have demonstrated, feedbacks are somewhat net-negative.
If my best guesses are indeed better than those of the IPCC, then climate sensitivity to a doubling of CO2 concentration is 0.8 K before feedbacks are taken into account and 0.7 K after feedbacks, very much in line with the results of Lindzen & Choi and Spencer & Braswell.
Even if the IPCC is right, it is still cheaper and more cost-effective to spend not a single red cent on global warming for at least 50 years (Nordhaus, 2012) than to take any action today to try to make global warming go away. Given that none of the three parameters whose product is climate sensitivity can be measured, it ought to be self-evident that the value of their product cannot be definitively determined, from which it follows that “the science” cannot possibly be “settled”.
Another commenter has asked why I insist on the use of reason in science and then admit that I believe in a Creator. Many leading scientists, including Professor Antonino Zichichi (president of the World Federation of Scientists) and Lord Kelvin (for whom the scale of absolute temperature is named) have been believers in Christianity. Thanks to Max Planck, it is now demonstrated that the laws of physics did not come into being until a fraction of a nanosecond after the Big Bang, from which it follows that no amount of ingenuity on our part can reveal to us what (or Who) said “Let there be light” and blazed the Universe into glorious existence.
In short, it is scientifically and rigorously proven that the assertion of Christianity that there is a Creator cannot be disproved (and, by the same token, that it cannot be proved either). Therefore, it is permissible for me to say I believe in the truths of the Christian faith, though it would be impermissible for me to say I could prove them to be true. On the other hand, many of the beliefs of the climate extremists can be demonstrated to be false. Their belief system, therefore, is appropriately classified not as a religion (which can neither be proved nor disproved) but as a superstition (which can be and has been disproved).
Finally, one or two commenters have expressed annoyance that I am willing to concede that there is such a thing as the greenhouse effect at all. The reason why I have always conceded this fact is that it is indeed a fact, established by an elegant, readily-replicable and oft-replicated experiment first conducted by an ancestor of one of the commenters here.
The true scientific debate does not center on whether there is a greenhouse effect (there is: get used to it), but on how much warming our enhancement of that effect may cause. My best guess is, “not a lot”. If we expect the climate extremists to be truthful, we ought to do our best to be truthful ourselves, and not to push the scientific argument beyond what measurement and experiment and the application of established theory to the results has plainly and sufficiently demonstrated.