Sunday, December 19, 2010

Socioeconic Trends in Climate Data is Published

“Socioeconomic Patterns in Climate Data” by Ross McKitrick and me (MN 2010) has just been accepted for publication by the Journal of Economic and Social Measurement. It can be accessed here. This paper is largely in response to Gavin Schmidt’s 2009 paper “Spurious Correlations…” (S09) that I have discussed earlier. S09 was published in the International Journal of Climatology (IJOC), which subsequently rejected an earlier version of MN2010. I was very happy to provide a bit of the work on this paper. In particular I did some analysis, some modeling, and helped a bit with the editing.
There is, as often seems to be the case in climate science, some heated discussion surrounding two distinct areas with our paper. First there is the question of whether we received a fair hearing in peer review from Journal of Climate. Second once again Gavin is saying that our conclusions are incorrect. I should add that he has done this without benefit of reading our actual paper, but it seems fairly clear that reading the paper will not change his mind.
For me there are two distinct fairness and good practice issues. First S09 was clearly a response on Ross’s earlier work. I’m sure this is too much to ask, but Gavin should have sent his paper to Ross for comments before publishing. It would have been the right thing to do scientifically, but I’m not sure how much this is about science. Failing Gavin doing that then IJOC certainly should have asked the author’s of the previous papers if they had comments. At the absolute minimum they should have offered space for responses in their publication. They didn’t do any of these things, and it doesn’t appear to me as if the reviewers of either S09 or MN2010 even read the predecessor papers. Second the objections to MN2010 from IJOC didn’t have to do with whether we were right. They had to do with whether they felt the predecessor papers were the right approach at all. But the problem is that they were different, and less specific, arguments than those in S09. The weird thing is that these comments weren’t themselves subject to peer review or response, so from IJOC’s perspective Gavin’s incorrect arguments were allowed to stand, because the reviewers had altogether different objections to Ross’s earlier work. In my opinion they should have asked us to submit a response rather than a paper in order to resolve the situation, but they didn’t.
In response to our paper Gavin is now making new technical arguments about why we are incorrect. The first argument is that he has drawn a graph that shows spatial autocorrelation (SAC) of the residuals. It is at least nice of him to acknowledge that the argument is S09 was incorrect, and that you need to look at the residuals. The problem is that he is still not doing any type of standard test for SAC. These are well known, and we have done those tests in our paper. This part is really amazing. I’m not an expert in this area, but back when I was looking at this I was able to quickly find a text on the subject and find these standard tests. Who would make a statistical argument without using the standard statistical tests in the literature? We have also shown the effect of allowing for SAC where necessary and that the results stand. So in my opinion that is what he needs to respond to. His second argument is that it is possible to see these types of correlations in a single instance of a GCM run. This will take a little more examining.
In S09 Gavin showed several GCM runs. Using those he showed that some economic variables were significant in the same regression. Since, of course, socioeconomic variables can’t be influencing a GCM this shows that these types of correlations are spurious. There are two problems. First, where they were significant the coefficients were very small, and of the opposite sign of those found with the real world climate data. Second, and rather ironically, if you allow for SAC they lose all significance, unlike those from real world climate data. In other words he managed to incorrectly argue that Ross’s earlier results were wrong because of SAC, and then make a flawed argument because he didn’t allow for SAC.
Now he is making a different argument, which is that if you do a whole bunch of GCM runs you will see a result exactly like Ross’s earlier work. The problem is that none of the runs in S09 look like that, and he isn’t producing any others. If he does then I guess we could take a look. Even if it does happen sometimes, and I guess it could as a matter of random outcomes, it would need to happen a lot for our conclusions to be incorrect. That is the whole idea of significance testing.
These results indicate urban heat island (UHI) and other measurement issues may be affecting the published long-term land temperature trends. I believe that this result is plausible given what is known about UHI and the lack of meta data for large portions of the world. The results also indicate that it is in fact areas where we have the least amount of meta data and the poorest records that are the most affected. Also remember that land makes up only one third of the Earth’s surface so even if there were a 50% error in land trends this would only be a 15% difference in the overall trend. Therefore this shouldn’t be an argument over the big picture. But people building models need accurate measurements of the various portions of the temperature trend, so they should be quite interested if corrections need to be made. The results of any one study aren’t definitive of course, but it should be taken seriously and additional work should be encouraged rather than huge amounts of energy and time being spent on spurious arguments trying to get rid of it.

Monday, August 2, 2010

Gavin Schmidt Weighs in On Oreskes

Over at Gavin Schmidt responded to a comment of mine by stating.

Having read Nicholas Nierenberg's paper and the relevant parts of MoD, the issue is in the interpretation of William Nierenberg's actions on the 1983 report. NN claims essentially that the WN synthesis was reflective of the consensus on the committee, Oreskes and Conway see it as slanted towards inaction. It is a pretty nuanced issue, and while I can see why the parties involved have taken the positions they have, I'm not convinced that there is any obvious resolution of these opinions. But having said that, this is but a small part of the O&C case, and the evidence that they bring together overall is very convincing.

To me this demonstrates that Gavin will bend over backward to support anyone with an aligned political viewpoint. It is hard to imagine how, after reading our paper, a scientist wouldn't be concerned about the standard of proof Oreskes uses. And it seems to me logical, given that he isn't reviewing the sources himself, that he would be concerned about whether the other chapters use the same standards of proof.

Saturday, July 3, 2010

Our Peer Reviewed Paper is Published

I have just been notified that our peer reviewed paper on the 1983 NAS report "Changing Climate" has been published. This paper completely refutes the claims of the "Chicken Little" paper by Oreskes et al. published in 2008. It has been a long but very rewarding process for me.

We initially submitted a paper that was a straight rebuttal of the Oreskes paper. We received an encouraging reply, but we were informed that either it would have to be greatly shortened and published as a reply, or it would have to be rewritten as an original paper. At first I found this discouraging, but I took the challenge and went back to review all the source materials available in the SIO archives, as well as a much broader selection of the existing literature. This allowed me to see the entire context of the story and how the publication of "Changing Climate" had actually occurred. In my particular case peer review was a strong positive, and made the result much better than my original idea.

The story actually starts with the Carter administrations push for synthetic fuels, and concern that this would exacerbate a problem that people were already starting to worry about. Ironically by the time "Changing Climate" was completed the synthetic fuels program had collapsed.

One thing that is still absolutely clear from all of this is that Oreskes got the story wrong.

I hope you enjoy reading about this piece of history. If anyone is interested in any of the underlying source documents I have images of all of them.

The paper is presented here by permission of the UC Press. Historical Studies in the Natural Sciences, Vol. 40, Number 3, pps. 318–349. ISSN 1939-1811, electronic
ISSN 1939-182X. © 2010 by the Regents of the University of California. All rights reserved.

Monday, May 24, 2010

Equilibrium Climate Sensitivity

I recently became interested in observational constraints to Equilibrium Climate Sensitivity (ECS), and as a result learned something new about the conclusions of the 2007 IPCC report. The reason for my interest is that I am finishing up the edits on the paper about the 1983 NAS report Changing Climate that was chaired by father. In almost every case that the report covered the scientific conclusions were virtually identical to the 2007 IPCC report. The most interesting difference was that they concluded that climate sensitivity to a doubling of CO2 was more likely in the bottom half of the 1.5-4.5C range. They based this on the observational record, and assumptions about CO2.

Quoting from the chapter authored by Weller.

"If the preindustrial CO2 concentration was near 300 ppm, the sensitivity of climate to CO2 (expressed as projected temperature increase for a doubling of CO2 concentration) might be as large as suggested by the upper half of the range of thestudy of the CO2/Climate review panel (1982), i.e., up to perhaps 4.5°C. However, if thepreindustrial concentration was well below 300 ppm, and other forcing factors did not intervene, the sensitivity must be below about 3°C to avoid inconsistency with the available record."

UPDATE: By well below the Weller panel was talking about something between 250ppm and 300ppm. Separately Machta reported that the pre-industrial concentration was in the range of 260-280ppm. Combining these findings it made sense that based on observation climate sensitivity might be in the lower half of the range.

ANOTHER UPDATE: Page 19 of the report synthesis shows that the 260-280 figure is "preferred." Page 33 of the report synthesis provides the .5C increase over preindustrial levels. Note that the monitoring panel didn't yet feel that this could clearly be attributed to CO2. These are both summarized from the relevant chapters.

For a long time while I was working on the paper, I just assumed that this conclusion had simply turned out not to be in the scientific mainstream. After all I had never heard of anything like that, and it had been 30 years. Lot's of time for new observations and scientific work. But then I noticed there was a section in the IPCC WG1 report on the subject of observational constraints on climate sensitivity. You can read the section for yourself (9.6.4 page 726), but here is the bottom line.

"Results from studies of observed climate change … indicate that ECS [Equilibrium Climate Sensitivity] is very likely larger than 1.5°C with a most likely value between 2°C and 3°C.” (The go on to point out that this supports the overall estimate of sensitivity as being 2-4C.)

That's exactly the same as saying that observations would put ECS in the lower part of the range. Which means that the 1983 report had it right. The only difference is that in 1983 the NAS was willing to include this in the executive summary, but for some reason in 2007 the IPCC wasn't.

Personally I can't imagine a scientific report summary which would place so little value on observation versus modeling that they wouldn't even mention that the observations would put sensitivity in the lower half of the range. It is fine with me if they would make that comment and then explain why they think the most likely figure of 3C is still correct, but to say nothing is really weird.

To me it seems pretty well buried, which feels more like politics than science, but to be fair I haven't asked anyone involved with the IPCC about it. I'm not even sure who to ask as the chapter conclusion speaks for itself.