Lindzen and Choi 2011: have they torpedoed AGW alarmism? Or not?

I have been arguing that Climate Sensitivity is the key to resolving the controversy over global warming.

Climate Sensitivity (CS) is the degree to which the earth's climate changes to a given change, conventionally taken as a doubling of CO2. The CO2 which we have already added to the atmosphere will push the heat up by ~1*C. Multiple lines of evidence (modelling, palaeoclimate, observations of volcano effects, solar cycles, ocean changes, and probabilistic)  all point to an additional 3*C (+or- 1.5*C)  increase due to positive feedbacks.

Note that the models underestimate CS if anything, because they do not take into account long-term feedbacks such as loss of ice and vegetation.

There is a detailed treatment of CS here.

The convergence on the 3*C value from six different approaches to the problem is remarkable, and very robust.

Climate skeptics must try to find evidence that CS is less than 1*C in order to prevent any damage to the profit lines of oil and coal companies.

I have mentioned Singer's attempt to do this here.

Spencer and Braswell tried and failed this year.

One other attempt of the sceptics to support their hypothesis is Lindzen and Choi 2009.  Their paper was strongly criticised , even from their own side, so they came up with a revision which they claim addresses the criticisms. It is published as Lindzen and Choi 2011.

Their paper estimates CS by comparing monthly 1985-2009 tropical sea surface temperatures with those at the top of the atmosphere. They conclude that climate models are exaggerating climate sensitivity. This conclusion was triumphantly seized on and amplified by the warming skeptic  blogosphere and mainstream press.

I have been waiting for an expert systematic refutation to turn up. John Cook of the excellent Skeptical Science site is about to put one up, but yesterday I found the peer reviews of LC11 from when they (unsuccessfully) submitted the paper to the Proceeding of the National Academy of Science - the US equivalent of our Royal Society.

Here I summarise the criticisms made by the reviewers:

1. The paper gives insufficient detail of the methods to allow other workers to reproduce them. This is a grade A, fundamental scientific error.
2. The paper does not address criticisms of LC09 by Trenberth et al 2010, nor Dessler 2010.
3. The paper studies only tropical processes, (a term that it fails to define) and unsafely assumes that this can be extended to the whole globe.
4. They ignore changes that occur over land.
5. They confuse forcing and feedback. In other words, they assume clouds to be causes, and not effects, of surface changes, and make no attempt to justify this assumption.
6. Month-to-month variability of the tropics may have nothing to do with climate feedback processes.
7. Detailed analysis of the "lagged regressions" (which are beyond my ken) show deficiencies.
8. The authors chose time periods for the lags that suit their conclusions.
9. The claim to deal with equilibrium climate sensitivity is not substantiated.

These are damning criticisms.

I cannot say whether any of these peer review criticisms were turned into amendments of the paper. PNAS rejected it, and Lindzen took it to the Asia-Pacific Journal of Atmospheric Sciences, who published.

The overall point is that this flawed paper gets published, is reported as the end to AGW in the blogosphere and conservative papers, and when the scientific community gets its act together, it will receive next to no coverage, leaving the public with the mistaken impression that AGW is "controversial".

It is not. All valid evidence points to Climate Sensitivity being in the region of 3*C - a value that merits serious decarbonisation of the world economy.

In future blog posts, I will deal with Idso 1998 and Shaviv 2005, which are the only other attempts to establish low sensitivity that I am aware of.

More on this from the excellent skeptical Science site.