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.
You left out Soon, Connolly and Connolly, 2015. It is described here: https://andymaypetrophysicist.com/2015/09/27/summary-of-soon-connolly-and-connolly-2015-re-evaluating-the-role-of-solar-variability-on-northern-hemisphere-temperature-trends-since-the-19th-century/
They demonstrate the ECS is less than 0.44 degrees C.
Thank you, Andy . I did not have access to the full paper, and this conclusion is not contained in the E-SR abstract.
If possible, Pierre Gosselin, please add this citation/summary ( to the (a) quantified section:
Soon, Connolly, and Connolly, 2015
http://www.sciencedirect.com/science/article/pii/S0012825215300349
http://globalwarmingsolved.com/data_files/SCC2015_preprint.pdf
Nonetheless, let us ignore the negative relationship with greenhouse gas (GHG) radiative forcing, and assume the carbon dioxide (CO2) relationship is valid. If atmospheric carbon dioxide concentrations have risen by ~110 ppmv since 1881 (i.e., 290→400 ppmv), this would imply that carbon dioxide (CO2) is responsible for a warming of at most 0.0011 × 110 = 0.12°C over the 1881-2014 period, where 0.0011 is the slope of the line in Figure 29(a). We can use this relationship to calculate the so-called “climate sensitivity” to carbon dioxide, i.e., the temperature response to a doubling of atmospheric carbon dioxide. According to this model, if atmospheric carbon dioxide concentrations were to increase by ~400 ppmv, this would contribute to at most 0.0011 × 400 = 0.44°C warming. That is, the climate sensitivity to atmospheric carbon dioxide is at most 0.44°C.
If CO2 doubles, so what?
Anthropogenic CO2 constitutes nothing more than a trace gas to begin with. Atmospheric CO2 = 0.04%, and human CO2 no more than ~$4% of that (or 0.0016% of total), summarizing all data I’ve seen, and I hope I’ve got my decimal places correct.
Water vapor makes up 1% (polar) to 4% (equatorial) of the atmosphere, and about 97% of the “greenhouse effect.” Anthropogenic CO2 is nothing more than a pinpoint in that.
I would love to see someone take those data and run with them to put warmistas on the defense.
If CO2 doubles, so what?
Anthropogenic CO2 constitutes nothing more than a trace gas to begin with. Atmospheric CO2 = 0.04%, and human CO2 no more than ~$4% of that (or 0.0016% of total), summarizing all data I’ve seen, and I hope I’ve got my decimal places correct.
Water vapor makes up 1% (polar) to 4% (equatorial) of the atmosphere, and about 97% of the “greenhouse effect.” Anthropogenic CO2 is nothing more than a pinpoint in that.
I would love to see someone take those data and run with them to put warmistas on the defense.
After all these years and all these papers still no explanations on CO2 supported science of global warming. The science of radiative heat transfer shows CO2 gas in the atmosphere is a coolant. There is some radiation reaching the surface from atmospheric CO2 but it will only warm surfaces colder than 243K (-30C).
Provided the Sun is not going to sleep for a few years as it happend in the Litle Ice Age.