I am reproducing this letter with the permission of Professor Brice Bosnich, a retired chemist and a fellow of the Royal Society. He sent it to Paul Nurse on his election as president of the society in 2010. Nurse did not reply.
Dear Professor Nurse
I am a retired professor of chemistry in The University of Chicago. I also am a Fellow of the Royal Society. First, allow me to congratulate you on becoming president of the Society. You are about to live in interesting times, I am sure.
Whereas I am reluctant to intrude on your time, I feel compelled to draw your attention to a very serious matter related to the Royal Society's position on man-made global warming (AGW). Beginning with the presidency of Bob May and continuing during the tenure of Martin Rees the Society has put forward a scientific case for (catastrophic) AGW, has joined with other academies in urging governments to take drastic action to reduce atmospheric CO2 concentrations, and, on occasions, has behaved as if it were a propaganda arm for the alarmist cause, . No one objects to individual Fellows having any view they wish on this matter, political or scientific, but I believe the Society should exercise great care in its public pronouncements. It should, I believe, resist taking overtly political or advocacy positions. Cautious, balanced and informed scientific arguments should be presented, the political implications of which should be left to the politicians.
If one goes to the Royal Society Web site one finds an especially poor, in places inaccurate, case made for catastrophic AGW, . There is also a highly speculative report on ocean acidification by CO2, , which seems to be based on a single paper, , that purports to calculate the change in ocean pH from 1750 to present! A change of 0.1 pH change was calculated! On this basis the report goes on to describe all imaginable catastrophes. At about the same time the Society's web page highlighted a paper about AGW and the shrinking sheep of St Kilda ! Then there was Bob May presenting an AGW lecture with the comprehensively discredited, , “hockey stick” graph as backdrop. I could go on.
How this state of affairs came about is a matter of speculation on my part. It is probable, however, that a group of committed Fellows persuaded the Society to take a position on AGW while the less conversant majority remained uncomfortably silent. Further, I fear the Society may have decided it was advantageous to blend its position with that of the existing government. I hope this is not the case.
Although I am not a climate scientist, I am sufficiently conversant with the climate science literature to be able to assess the issues accurately. My conclusion is that the case for catastrophic warming induced by man-made CO2 emissions is extremely weak (see for example, ). Allow me to encapsulate the issue, and forgive me if you are already familiar with the material that follows.
1.Following the (global) Medieval Warm Period where the temperatures were similar to those presently recorded, the earth entered the Little Ice Age. Since the end of the Little Ice Age (about 1850) the earth has warmed intermittently. The actual amount of warming is controversial for technical and possibly other reasons. For surface temperatures recorded by thermometer measurements, the amount of warming is probably less than reported . There is, however, no dispute that some near surface atmospheric warming has occurred,  .
2.Doubling the concentration of atmospheric CO2, which is projected to occur by the end of this century, will lead to an increase in temperature of about 1 degree C from the CO2 greenhouse effect. There is no dispute here. No one has suggested that a 1 degree C of "forcing" would be catastrophic.
3.In order to get to the 2 to 4 or more degrees C increase by 2100 as claimed by the IPCC, one has to invoke large positive feedbacks. For the case of the feedback by water vapor, as an example, the initial(CO2 induced) warming would generate an increase in atmospheric water vapor, a greenhouse gas, which itself will increase the temperature which, in turn, would generate more water vapor and so on. There are other feedbacks, most notably clouds, which combined with water vapor represent about 90% of the greenhouse effect. Contrary to what the Society’s Web site asserts, there was no (predicted) upper atmosphere signature found for water vapor feedback during the recent warming. The feedback from clouds is poorly understood as acknowledged by the IPCC. There is, however, accumulating evidence which suggests that the total feedback from all sources is zero or possibly negative (see for example, ). The evidence for the negative feedback case is substantially more persuasive than the IPCC assertion that it should be large and positive.
4.The only case that the IPPC makes for AGW is that they can't think of anything else that could have caused the recent warming and that models can reproduce the warming. This reproduction is achieved by introducing arbitrary amounts of aerosols. These same models did not predict the recent 12 years of constant temperatures.
5.Finally, there is an excellent correlation between the US postal rates since 1900 and global temperatures, . Thus the assertions that AGW is responsible for the shrinking sheep of St Kilda or the vanishing snows of Kilimanjaro or any other alarmist pronouncements do not establish that the warming is man-made. This should be obvious to Fellows of the Royal Society, many of whom have used such correlations to support the existence of catastrophic AGW.
The case for catastrophic warming rests solely on the sign and magnitude of the feedbacks. As has been often said, “Extraordinary claims demand extraordinary evidence”. The potential of catastrophic AGW is an extraordinary claim, but is without compelling supporting evidence. Because of the way that the AGW issue has been politicized together with the behavior of certain climate scientists, the reputation of science and the institutions that support it have suffered. Further, were catastrophic AGW to join the dreary parade of alarms that have punctuated the recent history of affluent societies, the consequences to science and the Society could be severe. It may take a long time before reputations are restored. It is, therefore, imperative for the Society to stay away from politics and advocacy of AGW or any other science based issue, no matter how beguiling the prospect may seem.
Below is the opening paragraph of a joint statement (2005) by several academies including RS and NAS. This statement urges governments to take action on AGW. I have reviewed it for accuracy and balance, see round bracketed highlighted comments. This has been done in order to illustrate the unease and frustration that I am sure many Fellows feel when they read these official pronouncements.
There will always be uncertainty in understanding a system as complex as the world’s climate (Correct, climate science is in its infancy). However there is now strong evidence that significant global warming is occurring (Is about 0.7 degrees C increase in 150 years evidence?). The evidence comes from direct measurements of rising surface air temperatures (No warming has occurred for the last 12 years and the recent rate of warming is about the same as the rate of rise for the period 1920 to 1940 when greenhouse gases were increasing more slowly, ), and subsurface ocean temperatures(No warming has occurred for 8 years, at least, , and sea temperatures have been varying up and down for at least 50 years, ), and from phenomena such as increases in average global sea levels(No significant change in the rate of rise of sea levels has occurred for at least 100 years,  ), glaciers retreating (Glaciers have been retreating and some reforming since the Little Ice Age, at least, , and there is no persuasive evidence to suggest that the retreat is accelerating), and changes to many physical and biological systems(Which ones, the sheep of St Kilda?). It is likely that most of the warming in recent decades can be attributed to human activities [IPCC 2001] (See above for this "evidence"). This warming has already led to changes in the Earth's climate (Climate is defined as more than 30 years of weather, so what are they trying to say? That 0.7 degree C or so rise in temperature is an indication of climate change?).
Similarly, the most recent Royal Society statement, issued jointly with the Met Office and NERC, is replete with misleading and inaccurate assertions, .
Finally, I note that the Society has enthusiastically endorsed the central recommendations of the Stern Review, . As noted by William Nordhaus, "the (Stern) Review should be read primarily as a document that is political in nature and has advocacy as its purpose". Moreover, Nordhaus makes a persuasive case that Stern has not got the economic assumptions right, especially on the crucial question of economic "discounting", . The Nordhaus argument, placed in a wider context, is given in, , where it is noted that when “Prudential Handicapping” is abandoned for the “Precautionary Principle” there are no guiding criteria for an impossibly expensive journey in the endless pursuit of a zero risk world. A recent assessment of these issues offers a prescription for dealing with climate change, from whatever source, that drastically differs from that advocated by the IPCC, Stern and by the Royal Society, . These and other social science studies indicate that it would be wise for statements from the Society to stay strictly within the bounds of (physical) science.
I end with a quotation from Atte Korhola, a Professor of Environmental Change at the University of Helsinki:
When later generations learn about climate science, they will classify the beginning of the twenty-first century as an embarrassing chapter in the history of science. They will wonder about our time and use it as a warning of how core values and criteria of science were allowed little by little to be forgotten, as the actual research topic of climate change turned into a political and social playground.
This letter is being sent to Martin Rees and to John Pethica. I should be grateful if you were to pass it on to members of Council.
 http://www.cmar.csiro.au/sealevel/images/CSIRO_GMSL_figure.jpg , http://www.agu.org/pubs/crossref/2009/2009GL038720.shtml