Now that the silly season has subsided,......
Gimlet wrote (post # 4):-
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The conclusion that a doubling of CO2 will have little effect has been known for a few years, all that seems to have changed is to reduce the effect.
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You are mistaken in accepting this conclusion.
A comprehensive study of attempts to estimate climate sensitivity can be found here:-
Climate sensitivity - Wikipedia, the free encyclopedia
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This value is estimated, by the IPCC Fourth Assessment Report as likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values.
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Interestingly, Climateprediction.net did one of those similations like the SETI project – using idle-time in participating home computers and came up with a range of less than 2° C to more than 11 °C, - however, the most reliable simulations suggested a figure of 3 deg C. i.e. supporting the IPCC. Worryingly, only very few predicted less than 2 deg C.
(see also the footnote)
So, interested to see how came to his conclusion, I noticed this at the tail end of the pdf. :-
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Recently he had trouble understanding how a rise of carbon dioxide, or any substance, in the atmosphere from such low values as 0.035 percent could have such an overly large influence on the Earth’s future temperature as some predict. So he decided to read and learn about this from the perspective of an individual with a technical background, but not in the field of climate.
After a few infrared measurements on summer nights showed that the amount of heat being radiated from the atmosphere was much less than some climate models predicted, he began an intensive study resulting in his own computer simulations based on available atmospheric data and well known laws of infrared physics.
While weather predictions and long-term climate and very complex and beyond the author’s expertise, he feels the single issue of heat absorption and radiation due to carbon dioxide is much simpler, well understood, and better modeled and
measured as proposed here. For reasons explained in the report, he went from being
unknowledgeable to skeptical to now very doubtful about a harmful future temperature rise due to increased carbon dioxide levels.
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‘Scuse me, I need to nip out to check if the Moon is in it’s correct position …..
Footnote:-
A global warming of about 5 deg C or above is widely regarded as being catastrophic – comparable to average temperatures estimated to be responsible for the last two Mass Extinctions. A rise to about 3 deg C is considered very dangerous because of the risk of unstoppable positive feedbacks like methane hydrate releases.