I reviewed the allegedly independent observational contraints on climate sensitivity All citations including surprisingly Shaviv are to some extent based on models with Shaviv explicitly relying upon Gregory for part of his work Gregory explicitly relied upon models for his estimate of heat flux into the ocean for the late 19th century and based other assumptions on model insights and results Annan relied upon models to analyze the maunder minimum and also mistakenly assumed the maunder was long enough to achieve equilibrium which is contradicted by climate commitment studies which estimate closer to 1000 years AR4 According to the draft of the fourth IPCC current models favor a climate sensitivity of about 3 degrees C with a narrowing of the range from previous versions See page 8 42 As discussed in Chapter 10 the current generation of AOGCMs covers a range of equilibrium climate sensitivity from 2 1 to 4 4 C with a mean value of 3 2 C Table 8 8 1 Chapter 10 Box 10 2 This page should be updated to reflect newer work at least once the final draft of the IPCC is released Better to use the SPM which is released I ve updated the page Baseline It would be good if a little more information were given possibly by links to other articles about the changes which constitute a doubling of CO2 It is not clear from this article that temperature is related to CO2 logarithmically or why it assumed to be so and so it might to people such as myself who would guess it was a linear relationship raise questions of when and where the doubling is measured from 280ppm 380ppm Also it could be clearer how N20 CH4 etc are included in the single CO2 parameter Thanks if anyone can add this The article doesn t talk about the T CO2 log relation nor is it clear that it should do Baseline everyone thinks of 280 but I m not sure this is necessary I agree that the logarithmic depndence of forcing on CO2 concentration needs justification It is interesting to consider the cooling that would result if the log relationship held true for reduction of CO2 as well as increases The earth s tmperature would drop to absolute zero before the CO2 conc reached zero Schwartz I removed Schwartz It too new and almost undoubtedly wrong I protest against POV deletion of peer reviewed literature If you can t see the obvious errors then you have shown yourself to be incompetent to comment If you can see the errors and want to include it regardless then you are dishonest please reread Wikipedia Assume good faith Also see Climate Insensitivity and AR 1 Models The issue doesn t appear to be as clear cut as you suppose I m not assuming anything merely pointing out two possible conclusions which appear to be exhaustive to me I don t find any support for Schwartz s analysis in the link you provided Regardless it is but one minor paper which is hardly representative of scientific opinion I had contributed the following para Schwartz 2007 advanced a new method of calculating Earth s climate sensitivity based on a whole Earth energy balance model According to this model the climate sensitivity can be determined empirically as the time constant characterizing fluctuations in global mean surface temperature determined from autocorrelation of the time series of that quantity divided by the effective heat capacity of the climate system determined from time series of ocean heat content and global mean surface temperature Based on a suggestion by Sca