....
Let's also not forget that methane, although a 'potent greenhouse gas', is not a big cause for concern in the atmosphere because water vapor will absorb electromagnetic radiation on it's spectrum of interest anyway. This is kind of like the principle that if one is already behind an armor plate, putting up some bullet-proof glass in front of it has little effect. See:
http://wattsupwiththat.com/2014/04/11/methane-the-irrelevant-greenhouse-gas/Good point.
I have always found Anthony Watts to be credible.
I don't think that Watts himself is a scientist, though he is reasonable well versed in the science due to immersion of nothing else. Most of the stuff on his site (including the article quoted) seem to be written by others in what he often calls 'guest posts.'
Someone (I think Dr. Salby) made mention of a related concept that even pure CO2, for instance, approaches a point in terms of concentrations where it has no more effect. The corresponding analogy would be if one is already behind an armor plate, more armor plates are not going to have much more of an effect. This makes some sense qualitatively but I've not run across a quantitative exploration of this principle in the various plausible atmospheric conditions that we might see.
I just scanned around the 2015 London Salby vid. Around the one hour mark he does some exploration of the impacts of burning every bit of fossil fuels that we can find, and he talks a little about the opacity curves calculated for increased CO2 concentrations. Interesting stuff (to me.) There seems to be very little love lost for Salby even among some of the most prolific of Watts's guest posters. I personally appreciate the guy's presentations though. It seems to me that his constructs line up with observation better than most.
He seems to be willing to throw out ALL of the 'science' produced under IIPC 'scientists.' (He also seems to be one pissed-off MF'r.) I wonder if some people are worried that such a giant disposal of current climate understandings might be a pill to big for almost anyone to swallow and thus he is as big a threat to the 'deniers' as he is to the 'warmanistas.'
Each doubling of CO2 concentration has a logarithmically DECREASING effect. This is very basic science. For example...
1x Co2 - "A" effect. Say for example, 1 degree F
2x Co2 - A/2 effect is 0.5F
4x Co2 - A/4 effect is 0.25F
8x Co2 - A/8 effect is 0.125F
This is utterly contrary to Warmers who persistently claim "points of no return" and "cap Co2 emissions at 400 ppm or face dire consequences" and on and on.
RE the bolded above, yes pretty much ALL the paragraphs of the IPCC reports can be thrown out, unless you want a handy reference to Warmer misrepresentations and omissions to support a government policy position. I am not saying throw out the underlying basis of scientific articles, only the IPCC reports. In many cases the underlying articles and knowledge base does not support the simplifications, generalizations, and politically correct conclusions in the report.
Further, the reports are strictly oriented to and for government policy makers. Thus they don't even pretend to be unbiased summaries of work in specific technical fields of science.