By Kenneth Richard
When it comes to climate’s sensitivity to increases the CO2 concentration, the commonly stated assumption – based on modeled calculations – is that the resulting temperature change when CO2 concentrations are doubled from 275 ppm (pre-industrial) to 550 ppm is about 1.2°C. This is the direct result reported from doubling CO2 concentrations without any feedbacks (primarily from water vapor or cloud cover changes).
Below is a summarizing quote from the IPCC pertaining to the climate’s sensitivity to direct CO2 increases:
If the amount of carbon dioxide were doubled instantaneously, with everything else remaining the same, the outgoing infrared radiation would be reduced by about 4 Wm-2. In other words, the radiative forcing corresponding to a doubling of the CO2 concentration would be 4 Wm-2. To counteract this imbalance, the temperature of the surface-troposphere system would have to increase by 1.2°C (with an accuracy of ±10%), in the absence of other changes.”
As well as another from the skepticalscience.com blog:
If there were no feedbacks in the Earth’s climate system, physics tells us climate sensitivity would be 1.2°C for a doubling of CO2.”
Although this temperature calculation of just over one degree Celsius for doubled CO2 is widely accepted in the scientific community – even by skeptics of the IPCC’s conclusions – many scientists have found a 1.2°C increase in surface temperature from doubled CO2 is still way too high.
Click here to go to the list of 60 papers that support the conclusion that doubling CO2 concentrations to about 550 ppm results in a much lower temperature increase than 1.2°C. The papers are divided into 3 categories: (a) quantified low CO2 climate sensitivity results (2X CO2 may cause just ~0.02 to 0.7°C of warming), (b) non-quantified low climate sensitivity results for doubling (or significantly increasing) CO2 concentrations, and (c) conclusions that increasing CO2 concentrations leads to a net cooling rather than a warming.