Curry vs. Mann in Discover

There is an interesting set of interviews in Discover with Judy Curry, of Georgia Tech, and Michael Mann, of Penn State. It is worth reading in full to see two very different views of climate science and how it should engage with the broader community. One of these voices represents the future of climate science, and the other, its recent past.

Here are some excerpts from the interview with Curry:

Where do you come down on the whole subject of uncertainty in the climate science?

I’m very concerned about the way uncertainty is being treated. The IPCC [the United Nations’ Intergovernmental Panel on Climate Change] took a shortcut on the actual scientific uncertainty analysis on a lot of the issues, particularly the temperature records.

Don’t individual studies do uncertainty analysis?

Not as much as they should. It’s a weakness. When you have two data sets that disagree, often nobody digs in to figure out all the different sources of uncertainty in the different analysis. Once you do that, you can identify mistakes or determine how significant a certain data set is.

Is this a case of politics getting in the way of science?

No. It’s sloppiness. It’s just how our field has evolved. One of the things that McIntyre and McKitrick pointed out was that a lot of the statistical methods used in our field are sloppy. We have trends for which we don’t even give a confidence interval. The IPCC concluded that most of the warming of the latter 20th century was very likely caused by humans. Well, as far as I know, that conclusion was mostly a negotiation, in terms of calling it “likely” or “very likely.” Exactly what does “most” mean? What percentage of the warming are we actually talking about? More than 50 percent? A number greater than 50 percent?

Are you saying that the scientific community, through the IPCC, is asking the world to restructure its entire mode of producing and consuming energy and yet hasn’t done a scientific uncertainty analysis?

Yes. The IPCC itself doesn’t recommend policies or whatever; they just do an assessment of the science. But it’s sort of framed in the context of the UNFCCC [the United Nations Framework Convention on Climate Change]. That’s who they work for, basically. The UNFCCC has a particular policy agenda—Kyoto, Copenhagen, cap-and-trade, and all that—so the questions that they pose at the IPCC have been framed in terms of the UNFCCC agenda. That’s caused a narrowing of the kind of things the IPCC focuses on. It’s not a policy-free assessment of the science. That actually torques the science in certain directions, because a lot of people are doing research specifically targeted at issues of relevance to the IPCC. Scientists want to see their papers quoted in the IPCC report.

And here is an excerpt from Mann's interview:

Judith Curry has been an outspoken critic of your work and of a lot of climate researchers in general.

Did you ask Judith to turn over her e-mails from the past three years? Once she does that, then she’s in a position to judge other scientists. Until she does that, she is not in a position to be talking about other scientists. Glass houses. Look, I’ll just say this. I’ve received e-mails from Judith that she would not want to be made public.

She said that some data discussed in these e-mails concerned a temperature bump in the 1930s and 1940s, caused by a coincidence of Atlantic and Pacific decadal oscillations.

Yeah, I came up with the term: Atlantic Multidecadal Oscillation. I coined the term in an interview with Richard Kerr [a writer for Science] in 2000 over a paper with Tom Delworth of the Geophysical Fluid Dynamics Laboratory and the NOAA Laboratory in Princeton, where we actually were the ones to articulate the existence of this oscillation. And you know what? It was celebrated by contrarians. My work has been celebrated by climate skeptics. It’s an interesting footnote.

Is Curry wrong in that regard?

I don’t know exactly what she is referring to. She might be referring to a paper by Thompson et al. that appeared in Nature a couple of years ago about a spurious cooling in the 1940s that scientists couldn’t quite understand.

She was referring to a rise and fall in temperatures in the 1930s and ’40s that might have been caused by a coincidence of these oscillations in the Atlantic and Pacific, and another that could account for a lot of the warming in the 1990s. She was saying that it looked bad that you were trying to smooth out the bump in the ’30s and ’40s but not the one in the 1990s. Is that a valid critique?

The way you characterize it, it sounds like nonsense. I’m not sure how much familiarity she has, for example, with time-series smoothing. I’ve published a number of papers on this topic, and in fact, the approach that I take was used in the most recent IPCC report. I actually take a very objective approach to the problem of time-series smoothing. I’m not sure she understands the problem. It is very much the mainstream view in the climate research community that you cannot explain the warming of the past few decades without anthropogenic and human influences on climate.

Read the whole thing.