Where does climate science go from here? The Copenhagen talks were a dud. Stolen e-mail correspondence has embarrassed some leading climatologists. If the science is settled and the threat is urgent, why has global warming become a soap opera? To find out, DISCOVER sought two different, important views, from Penn State’s Michael Mann and Georgia Tech’s Judith Curry.
Judith Curry
School of Earth and Atmospheric Sciences
What was your reaction to the scandal over stolen e-mail?
I sympathize a bit with the guys who got caught out in the e-mail hack. I know what it’s like to be under that kind of attack, and it’s not pleasant. We were attacked pretty soundly in the media [for a 2005 paper showing that the frequency of intense hurricanes has almost doubled in the past 30 years]. We had firsthand experience dealing with climate skeptics, amplified by advocacy groups like the Competitive Enterprise Institute and a lot of the think tanks that were allegedly funded by ExxonMobil and other firms. Six months later, though, we had sorted things out and were talking to scientists on the other side of the debate. We ended up making pretty good progress on the hurricane story as a result. Compare that with the “hockey stick” story, where there’s been a war for six years running.
The hockey stick—Michael Mann’s widely cited graph of average temperatures in North America over the past 1,000 years—was attacked by two prominent critics, Steven McIntyre, a former mineral company executive, and Ross McKitrick, an economics professor at the University of Guelph in Canada. Where does that dispute stand?
One would have hoped it would have an outcome similar to the hurricane story, but the hockey stick thing was exacerbated by Michael Mann’s behavior, trying to keep the data and all the information away from McIntyre, McKitrick, and other people who are skeptical of what they were doing. So we’ve just seen this blow up and blow up and blow up, and it culminated in the East Anglia hack and the e-mails that discredited those guys quite a bit. This made us reflect on the bigger issues of how scientists should be interacting with the media and how we should be dealing with skeptical arguments. I think the way that Mann and Phil Jones [the former director of the Climatic Research Unit at East Anglia, who resigned over the scandal] and those guys were going about it was wrong, not just in terms of ethics. It also backfired.
What motivated you to speak out?
When this hit, I was probably more ready than many others to respond because I’d been thinking about these issues for a number of years.
Do you find it hard to get people to talk about climate change without being evangelical?
I put myself in the middle, and I’m taking fire from both sides. Neither side is happy with what I’m doing. Obviously, people like Michael Mann are offended by what I’m saying [about the shortcomings of climate science], and I have received an e-mail from one of the people involved in the East Anglia e-mails who’s not happy with what I’m doing. The so-called skeptics think I’m just trying to cover myself. But I’m not personally involved in any of this, other than that I’ve been thinking about these issues for a long time, and there are certain things I felt compelled to say.
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.
You’ve talked about potential distortions of temperature measurements from natural temperature cycles in the Atlantic and Pacific oceans, and from changes in the way land is used. How does that work?
Land use changes the temperature quite a bit in complex ways—everything from cutting down forests or changing agriculture to building up cities and creating air pollution. All of these have big impacts on regional surface temperature, which isn’t always accounted for adequately, in my opinion. The other issue is these big ocean oscillations, like the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, and particularly, how these influenced temperatures in the latter half of the 20th century. I think there was a big bump at the end of the 20th century, especially starting in the mid-1990s. We got a big bump from going into the warm phase of the Atlantic Multidecadal Oscillation. The Pacific Decadal Oscillation was warm until about 2002. Now we’re in the cool phase. This is probably why we’ve seen a leveling-off [of global average temperatures] in the past five or so years. My point is that at the end of the 1980s and in the ’90s, both of the ocean oscillations were chiming in together to give some extra warmth.
If you go back to the 1930s and ’40s, you see a similar bump in the temperature records. That was the bump that some of those climate scientists were trying to get rid of [in the temperature data], but it was a real bump, and I think it was associated with these ocean oscillations. That was another period when you had the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation chiming in together. These oscillations and how they influence global temperature haven’t received enough attention, and it’s an important part of how we interpret 20th-century climate records. Rather than trying to airbrush this bump in the 1940s and trying to get rid of the medieval warm period—which these hacked e-mails illustrate—we need to understand them.
They don’t disprove anthropogenic global warming, but we can’t airbrush them away. We need to incorporate them into the overall story. We had two bumps—in the ’90s and also in the ’30s and ’40s—that may have had the same cause. So we may have exaggerated the trend in the later half of the 20th century by not adequately interpreting these bumps from the ocean oscillations. I don’t have all the answers. I’m just saying that’s what it looks like.
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