“To talk about global cooling at the end of the hottest decade the planet has experienced in many thousands of years is ridiculous.” Ken Caldeira, Climate Scientist 
“You’ve all seen articles saying that global warming stopped in 1998. With all due respect, that’s being a little bit unfair to the data.” Pat Michaels, Climate Scientist 
Dear Dr. Pat Michaels
I write and edit a column called “Sustainable Planet”  for a small local internet news paper in Northern Virginia called the Blue Ridge Leader. With this open letter, I’m asking if you wouldn’t mind describing your view on anthropogenic global warming (AGW) for my readers. We are specifically interested in the science and not policy or economics.
The science in support of Svante Arrhenius’ theory of AGW is assessable, unambiguous and coherent. We can begin with the four IPCC reports but can add to that record a host of text books related to earth sciences and climate physics [see fore example 4 and 5]. There are several really good review papers and one by Stefan Rahmstorf is especially helpful . The video of Richard Alley’s invited lecture at last year’s American Geophysical Union conference summarizes the paleoclimate record and the impact of atmospheric carbon dioxide on Earth’s climate . The peer-reviewed literature is compelling and overwhelmingly in support of the theory as several studies have demonstrated, the latest being Anderegg et al. . Furthermore Arrhenius’ theory is consistent will all science from microbiology  to astrobiology .
By contrast it is hard to find any science supporting the denialist  view. Not only is this science sparse as evident by reference , but it is obscured by the noisy and obfuscating nature of denialist arguments, most of which ignore data, and contradict each other as well as the laws of physics, or simply are outrageous attacks on individuals such as James Hansen, Michael Mann or Al Gore. The vast sea of arguments on policy or economics is an attempt to put the cart before the horse while the horse has already galloped off in the other direction. The denialist canard that global warming stopped in 1998 is typical of arguments which ignore data and contradict physical laws.
Each year Heartland Institute hosts a global warming denier conference. On March 2, 2008, you were their keynote speaker. The focus of your talk was the disingenuousness of this particular global warming denialist argument. You said, addressing the room full of deniers: “You’ve all seen articles saying that global warming stopped in 1998. With all due respect, that’s being a little bit unfair to the data.” You then went on to describe why. Peter Sinclair captured your candid admission in this informative youtube video . While you are more charitable, you are in complete agreement with Ken Caldiera. That puts you in good company.
You opine “Make an argument that you can get killed on and you kill us all.” Your meaning, I presume, is that if many denialists make arguments that are easily debunked all global warming denialists, including yourself, will lose their credibility. You conclude: “Global warming is real and the warming in the second half of the twentieth century, people had something to do with it.” In the Cato Institute handbook for policy makers  you repeat this sentiment: “Global warming is indeed real, and human activity has been a contributor since 1975.”
Physics teaches us that a doubling of atmospheric carbon dioxide will result in a radiation imbalance of 4 Watts per meter squared (W/m2) which will directly cause the Earth to warm about 1 degree C. Your article in the Cato Handbook aligns to this view. The difference between your view and the consensus view is related to the strength of feedbacks in the Earth’s climate system. As you point out water vapor is a greenhouse gas and as the Earth temperature climbs as a result in increased atmospheric carbon dioxide, more water evaporates off the oceans. This additional water vapor reinforces the warming. You don’t mention but I’m sure you agree that as the temperature climbs, snow and ice at the poles melts. The exposed darker dirt and water absorb more of the short wave solar energy than the white ice and snow once did, further reinforcing the warming. In addition, warm ocean water holds less carbon dioxide than cold water, thus as the oceans warm the equilibrium point between the atmosphere and ocean changes. These are positive feedbacks. Most identified carbon cycle feedbacks are positive. The consensus view, the view defended in the IPCC reports, is that including these feedbacks the equilibrium climate sensitivity, the amount the Earth’s surface will warm as a result of a doubling of atmospheric carbon dioxide is between 1.5 and 4.5 degrees C.
James Hansen’s view as described in  is that equilibrium climate sensitivity may be as high as 6 degrees C. This high value does not contradict the consensus view which, as you know, does not rule out the possibility of higher values.
In contrast, your view, if I’m interpreting your policy paper correctly, is that climate sensitivity is very low, 1 degree C or less. This view is outside the bounds of the consensus view. It means that all of these positive feedbacks must be counterbalanced by some unspecified negative feedbacks. Pointedly, you do not describe any of these possible negative feedbacks. In other words, your paper does not address the physics. Your paper is an attempt to defend a policy based on conservative ideology, and not a defense of your scientific view. This paper ignores the fact that policy that is not based on credible science or reality can’t help but be bad policy.
What would be helpful instead is a high quality paper defending your opinion that equilibrium climate sensitivity is indeed dominated by unidentified negative feedbacks and therefore that though the Earth’s surface will warm as a result of human emissions of carbon dioxide, the warming will not be very great. Your policy paper does not do this. Your logic is based on one peer-reviewed reference, from a May 2008 article in Nature by Noel Keenlyside et al. . Figure 4 from Keenlyside’s paper (see below) shows that they are forecasting temperature (the green curve) to end up in exactly the same place as the IPCC scenarios which you cite (the black curve). The measured temperature is shown in red and falls in between.
Keenlyside is forecasting a hot climate than hotter. It does not support your hypothesis. I recommend Joe Romm’s blog, including interviews with the authors, in order to better understand Keenlyside’s results . Keenlyside’s forecasts are somewhat controversial and already underestimating warming that is happening, so it is not clear that even if you had interpreted it correctly that this is the best reference to be using. A paper by Rind and Lean should also be considered .
My request by this open letter is if you wouldn’t mind describing for us what your scientific view is on this important issue including references. I am not looking for a paper of comparable high quality and completeness as the Hansen paper. I am assuming that perhaps such a paper or papers may already exist in the peer-reviewed literature. My concern is that science supporting denialist point of view is obscured by the ludicrous nature of most denier argument. This makes it a difficult and tedious exercise to uncover. If you could summarize where in the scientific literature possible negative feedbacks are described and verified in the paleoclimate record or by analysis, this would be much appreciated.
At Sustainable Loudoun, we are skeptics and appreciate good references and then validate them. But we do not discriminate. We hold everybody’s feet to the fire, especially our own.
Best regards and thank you kindly
 Kump, L. R., Kastings, J. F., and Crane, R. G., The Earth System, 2004.
 Lunine, J. I., Earth, Evolution of a Habitable World, 2000.
 Rahmstorf, S., 2008: Anthropogenic Climate Change: Revisiting the Facts. In: Global Warming: Looking Beyond Kyoto., E. Zedillo, Ed., Brookings Institution Press, Washington, pp. 34-53
 R. Alley, 2009, http://www.agu.org/meetings/fm09/lectures/lecture_videos/A23A.shtml
 Anderegg, W., Prall, J., Harold, J., and Schneider, S., Expert credibility in climate change, Proceedings of the National Academy of Science, 2010.
 Gaines, S., Eglinton, G. and J. Rullkotter, Echoes of Life, Oxford, 2009.
 Plaxco, K., and Gross, M., Astrobiology, Johns Hopkins University Press, 2006.
 The science journal Nature referred to AGW skeptics as denialist in an editorial on so called climate-gate. “…denialists use every means at their disposal to undermine trust in scientists and science.” Nature Editorial Staff, Vol 462 | Issue no. 7273 | 3 December 2009
 Michaels, 2009, http://www.cato.org/pubs/handbook/hb111/hb111-45.pdf
 Hansen, J., Sato, M., Kharecha1, P., Beerling. D., Robert Berner, R., Masson-Delmotte, V., Pagani. M., Raymo, M., Royer, D. and Zachos, J., “Target Atmospheric CO2: Where Should Humanity Aim?” The Open Atmospheric Science Journal, 2008, 2, 217-231.
 Keenlyside, N., Latif, M., Jungclaus, J., Kornblueh, L., and Roeckner, E., Advancing decadal-scale climate prediction in the North Atlantic sector, Vol 453| 1 May 2008| doi:10.1038/nature06921.
 see http://climateprogress.org/2008/05/02/nature-article-on-cooling-confuses-revkin-media-deniers-next-decade-may-see-rapid-warming/ and http://climateprogress.org/2009/10/01/interview-with-dr-mojib-latif-global-cooling-revkin-morano-george-will/ and http://climateprogress.org/2010/01/11/foxnews-wattsupwiththat-climatedepot-daily-mail-article-on-global-cooling-mojib-latif/
 Lean, J., and Rind, D., “How will Earth’s surface temperature change in future decades?”, GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L15708, 5 PP., 2009 doi:10.1029/2009GL038932