by Judith Curry
The skeptics thread has shown that it is plausible to be skeptical of a number of issues regarding the findings of IPCC WG1. However, whether atmospheric gases such as CO2 (and H20, CH4, and others) warm the planet is not an issue where skepticism is plausible.
Nevertheless, we have seen serious arguments (and even publications) against this theory:
The authors of these arguments believe that they should be convincing to other scientists. In that sense, these are serious arguments. While these arguments use physics, they are nevertheless erroneous. The G&T paper has been rebutted by Halpern (aka Eli Rabett), Colose et al., with a subsequent retort by G&T (both groups seem to be talking past each other). Are there any others? I am also unaware of rebuttals to Johnson?
The fact that such papers are being written by scientists who take themselves seriously and are being published implies to me that scientists have done a poor job of explaining and making the case for warming of the planet by gases such as CO2. Its easy to roll our eyes and mutter “cranks” when we see something crazy such as the sophistry in the little pamphlets put out by various anti-AGW advocacy groups. But these arguments refuting atmospheric warming by CO2 are being made by scientists that take themselves seriously on this issue.
So what have we been doing wrong in terms of explaining this, to other scientists, the technically savvy public, and the broader public? Our general argument consists of the following elements:
- a narrative with history, usually starting with Fourier, Tyndall, Arrhenius (see for example Weart, Wikipedia)
- the analogy to a greenhouse
- evidence for the existence of the planetary greenhouse effect (e.g. effective black body temperature, spectral IR measurements)
- the IPCC consensus
Well, #2 and #4 hinder rather than help. The greenhouse analogy has not served the scientific analogy very well, made painfully obvious by the G & T paper; John Nielsen-Gammon has a lucid new post on this, which looks like the start of an interesting series. The IPCC reports never actually explain the physics of the greenhouse gas mechanism. The explanations you find in popular books and undergraduate texts mainly address the issue from some combination of points #1, #2, #2.
There are graduate level texts on atmospheric radiative transfer, including:
- Goody and Yung
- Thomas and Stamnes
- see here for Georgia Tech’s radiative transfer course, this is a really good site with .ppt lectures and lab (computational) modules.
Once you digest one of these books, you will have no trouble understanding how this works. However, these texts are pretty heavy going in terms of physics and maths.
There is a big gap between the simple explanations and the radiative transfer texts. The blogosphere has stepped in to fill the gap. Good explanations that I have come across are:
- Real Climate
- Chris Colose
- Skeptical Science
- presumably there are others that I’ve missed?
However, a gap remains in terms of explaining the actual physical mechanisms. Yes, these sites give good explanations of the basic physics of radiative transfer and the Earth’s radiative energy balance, and provide empirical evidence for the existence of the greenhouse effect. But a good mechanistic explanation of the physical processes occurring seems absent, including an explanation of how local thermodynamic equilibrium is established in response to the absorption of infrared radiation by a small number of molecules. I don’t have a full understanding of what the actual issues are with the greenhouse effect skeptics (I suspect that Roy Spencer is painfully aware), but I have just received a copy of Slaying the Greenhouse Dragon, which I will read this weekend.
I don’t think the issue of not or mis- understanding the greenhouse effect is salient just for the public and a few seemingly confused scientists. I have to wonder how many scientists on the PNAS list that supports the consensus (including the biologists and economics) actually have a good understanding of the physical processes and have taken a graduate course in atmospheric radiative transfer.
We need to raise the level of our game in terms of explaining the planetary warming by infrared absorption of CO2 etc. The missing area of understanding seems to be the actual physical mechanism. Lets target an explanation at an audience that has taken 1 year each of undergraduate physics and chemistry, plus calculus. Once we have something that is convincing at this level, we can work on how to communicate this to the interested public (i.e. those that hang out in the climate blogosphere). Willis Eschenbach’s help is needed in translating this for the WUWT crowd.
Moderation note: this is a technical thread and comments will be moderated for relevance.