Thanks everyone who has responded so far. There is no such thing as an irrelevant, insignificant or distracting lead in what is becoming a major quest.
Most frightening response received so far: “… but with out the multiplier we don’t get enough co2 warming from the models and since we don’t know what else it could be it must be the co2”
The author of that will not give permission to publish our communications and I will not identify them other than to say they are a frequently published and well-known climate researcher. I would be embarrassed to have it attributed to me, too.
It seems likely we will need everything we can get on the original CO2 saturation chamber experiments too, so, if someone has a source…
Thanks again for the assist so far
As regular readers know I’ve been on a Quixotic quest to try to establish how climate models manage to take sensible inputs and return what may best be described as utter rubbish.
Part of this of course requires establishing the provenance of certain steps – in particular the marvelous magical multipliers and I am hoping JS readers can be of assistance.
I’ll leave this post sticky for a day or two – new items below:
The following is from The National Academy of Sciences: Climate Change: An Analysis of Some of the Key Questions, pp 6-7
The sensitivity of the climate system to a forcing is commonly expressed in terms of the global mean temperature change that would be expected after a time sufficiently long for both the atmosphere and ocean to come to equilibrium with the change in climate forcing. If there were no climate feedbacks, the response of Earth’s mean temperature to a forcing of 4 W/m2 (the forcing for a doubled atmospheric CO2) would be an increase of about 1.2°C (about 2.2°F). However, the total climate change is affected not only by the immediate direct forcing, but also by climate “feedbacks” that come into play in response to the forcing. For example, a climate forcing that causes some warming may melt some of the sea ice. This is a positive feedback because the darker ocean absorbs more sunlight than the sea ice it replaced. The responses of atmospheric water vapor amount and clouds probably generate the most important global climate feedbacks. The nature and magnitude of these hydrologic feedbacks give rise to the largest source of uncertainty about climate sensitivity, and they are an area of continuing research.
As just mentioned, a doubling of the concentration of carbon dioxide (from the pre-Industrial value of 280 parts per million) in the global atmosphere causes a forcing of 4W/m2. The central value of the climate sensitivity to this change is a global average temperature increase of 3°C (5.4°F), but with a range from 1.5°C to 4.5°C (2.7 to 8.1°F) (based on climate system models: see section 4). The central value of 3°C is an amplification by a factor of 2.5 over the direct effect of 1.2°C (2.2°F). Well-documented climate changes during the history of Earth, especially the changes between the last major ice age (20,000 years ago) and the current warm period, imply that the climate sensitivity is near the 3°C value. However, the true climate sensitivity remains uncertain, in part because it is difficult to model the effect of cloud feedback. In particular, the magnitude and even the sign of the feedback can differ according to the composition, thickness, and altitude of the clouds, and some studies have suggested a lesser climate sensitivity. On the other hand, evidence from paleoclimate variations indicates that climate sensitivity could be higher than the above range, although perhaps only on longer timescales.
The 4W/m2 appears to be a rounding of the IPCC’s 3.7W/m2 and is not a significant concern, at least not yet.
The 1.2 °C surface response comes from saturation chamber tests with a dry atmosphere and will need to be dealt with separately but what is the provenance of the 2.5 times amplification factor?
Surely they cannot mean Hansen’s absurd paleoclimate models that do not include any change in insolation?
Or can they?
Global climate forcing was about 6 1/2 W/m2 less than in the current interglacial period. This forcing maintained a planet 5 °C colder than today. (Can we defuse The Global Warming Time Bomb? naturalSCIENCE, August 1, 2003) — the text is slightly more specific: “This forcing maintains a global temperature difference of 5 °C, implying a climate sensitivity of 3/4 ± 1/4 °C per W/m2.” The Scientific American version, March 2004, is also available here as 310Kb .pdf.
Undeniably 4W/m2 at 0.75°C/(W/m2) yields the magical 2xCO2 = 3°C but somewhere there must be a reason or justification for this leap of faith.
If anyone knows or can find the provenance of this marvelous magical multiplier then do please leave a comment or if you really seek anonymity then e-mail editor at junkscience.com and I’ll keep you off-the-books.
Basic info on dry-air saturation chamber experiments would also be greatly appreciated.