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It's Gettin' Hot in Here: The Big Battle Over Climate Science

Two eminent climatologists share much different views

By Fred Guterl
Oct 20, 2010 12:00 AMOct 8, 2019 7:09 PM


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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. 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.

Judith Curry heads the Georgia Tech School of Earth and Atmospheric Sciences. Photography by Imke Lass

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.

What about risk? Isn’t it worth heading off even a small risk of catastrophe?  Oh, absolutely.

How does the lack of uncertainty analyses affect the calculation of risk?  You can think of risk as what can happen multiplied by the probability of its actually happening. The IPCC gives the whole range of things that could happen, some that involve a small amount of warming and some involving rather large amounts of warming. In terms of how probable each of those is, there’s a lot of debate, but in terms of actually making policy, you have to look at all possibilities and figure out possible actions you could take to limit the damage from climate change. Then you need to put price tags on each of these. With that kind of information, you can decide the policies you want to adopt and how to spend your money. I don’t think that whole analysis has really been thoroughly done. The UNFCCC has focused on one policy—carbon cap-and-trade and emissions reductions. There’s a whole host of others. Even if you’re focused on limiting CO2, there are taxes, and there is the possibility that through technology the problem will solve itself without cap-and-trade or a carbon tax. On the adaptation and geoengineering side, there’s a whole host of possibilities. These haven’t been assessed. Instead we’ve been fighting this little war over science.

Should we wait to resolve all the uncertainty before taking action?  The probability of something bad happening is at least as high as the probability that there were weapons of mass destruction in Iraq. That turned out not to be true, but we ended up going in there anyway. So we have a history of taking action on bad things that have a low probability of happening.

Is it fair to say that the kind of open inquiry you are calling for isn’t being done because scientists have been trying to convey a focused message to the public?  That’s part of it. You heard that in the [hacked] e-mails: Let’s simplify the story for the IPCC. But that’s just not how science is. The scientists have gotten caught in these wars with the media and the skeptics. They spend so much energy trying to put them down, energy that isn’t going into uncertainty analysis and considering competing views. I don’t think the scientists have personal political agendas. I think it’s more hubris and professional ego.

Do you agree that the Copenhagen meeting was a disaster?  Yes, it was.

So where does climate research go from here?  I personally don’t support cap-and-trade. It makes economic sense but not political sense. You’re just going to see all the loopholes and the offsets. I think you’re going to see a massive redistribution of wealth to Wall Street, and we’re not going to reduce the carbon dioxide in the atmosphere. We need a massive investment in technology. We do need to help the developing world that is most vulnerable now to the impacts of climate variability, not even the stuff that’s related to carbon dioxide. There are a lot of things going on—floods, hurricanes, droughts, and whatever—that can’t even be attributed to global warming right now. By reducing the vulnerability of the developing world to these extreme events, we’ll have gone a long way to helping them adapt to the more serious things that might come about from global warming.

Do you think the IPCC is going to have a reduced role?  If they are going to continue to be relevant, they need to tighten up their act in terms of making the process more open and transparent. How do you actually get to be a lead author of the IPCC? I have no idea who actually makes those selections. Things like that. All the data sets need to be out there and available and documented, so we don’t have these issues that we ran into with the hacked e-mails. The UNFCCC has become a big free-for-all. The G20, or some other group of nations, is where you’re going see the action.

Do you subscribe to the argument that today’s climate models are crude and need to be taken with a grain of salt?

No, I think the climate models are becoming quite sophisticated. We learn a lot from the simulations. But you have to keep in mind that these are scenario simulations. They’re not really forecasts. They don’t know what the volcano eruptions are going to be. They don’t know what the exact solar cycles are going to be. There will be a whole host of forcing uncertainties in the 21st century that we don’t know.

You’ve said that climatologists should listen more to bloggers. That’s surprising to hear, coming from a scientist.

There are a lot of people with Ph.D.s in physics or chemistry who become interested in the climate change story, read the literature, and follow the blogs—and they’re unconvinced by our arguments. There are statisticians, like McIntyre, who have gotten interested in the climate change issue. McIntyre does not have a Ph.D. He does not have a university appointment. But he’s made an important contribution, starting with criticism of the hockey stick. There’s a Russian biophysicist I communicate with who is not a climate researcher, but she has good ideas. She should be encouraged to pursue them. If the argument is good, wherever it comes from, we should look at it.

What about arguments on talk radio? No, we debunk those once and then move on.

Is there a denial machine? It’s complicated. The denial thing is certainly not monolithic. The skeptics don’t agree with each other at all. The scientific skeptics—[hurricane forecaster] Bill Gray and [MIT meteorologist] Dick Lindzen and [University of Alabama climatologist] Roy Spencer—criticize each other as much as we criticize them.

You wrote an article for climateaudit.org, a conservative Web site. Are people now calling you a denier?

No, they’re calling me naive. I stepped off the reservation, clearly.

Are you taking a career risk? A couple of people think so, but I’m senior enough and well-established enough that it doesn’t matter. I also live in Georgia, which is a hotbed of skeptics. The things I’m saying play well in Georgia. They don’t play very well with a lot of my colleagues in the climate field.

Does it bother you that skeptic has become a bad word? It’s an unfortunate word. We should all be skeptical of all science. The word denier has some unfortunate connotations also. I use “scientific skeptics” versus “political skeptics.” A scientific skeptic is somebody who’s doing work and looking at the arguments. A political skeptic is somebody who is getting the skepticism from talk radio.

Michael Mann is the director of Pennsylvania State University's Earth System Science Center. Photography by Imke Lass

Ever since his “hockey stick” graph of rising temperatures figured prominently in Al Gore’s An Inconvenient Truth, Mann has been at the center of the climate wars. His e-mail messages were among those stolen and widely published last November.

Let’s talk about the hacked e-mails and the ensuing climategate scandal. What happened? My understanding—and I only know what I’ve read from other accounts—is that hackers broke into the Climatic Research Unit of the University of East Anglia and stole thousands of e-mail messages, which they then proceeded to distribute on the Internet. They even tried to hack into a Web site that I help run, called RealClimate.

Does anybody yet know where the attack came from? No. There are many of us who would really like to know because obviously this is a serious criminal breach. And yet there’s been very little discussion, unfortunately, about the crime.

Who might have done the hacking? It appears to have been extremely well orchestrated, a very professional job. There also appears to have been a well-organized PR campaign that was all ready to go at the time these e-mails were released. And that campaign, involving all sorts of organizations that have lobbied against climate change legislation, has led some people to conclude that this is connected to a larger campaign by special interests to attack the science of climate change, to prevent policy action from being taken to deal with the problem.

Are you talking about the so-called denial machine? These aren’t my own inferences. I’m talking about what I’ve read on other sites. Interestingly enough, in the January 14, 2010, issue of Nature, there is a review of a book called Climate Cover-Up, by James Hoggan and Richard Littlemore, which details what I’ve just described to you. Back in 2006 there was a perfect storm of sorts. The IPCC had just come out with stronger conclusions. Al Gore’s movie inspired people to get interested in climate change. We had some hot summers; we had some very destructive hurricane seasons. To say hurricane Katrina was an indication of climate change is no more correct than saying the current cold outbreak is evidence against climate change—I mean, that’s weather—but it does influence people. A lot of things came together. There was a concerted effort by special interests who are opposed to policies to combat climate change to retrench and fight even harder in their campaign to discredit the science. There has been a lot more misinformation and, indeed, disinformation about climate change in the public discourse since then.

What about the e-mails themselves? Was it embarrassing having them brought to light? Nobody likes having their personal e-mail exposed. We can all imagine, I think, what that would be like.

There’s an investigation at Penn State, where you work, into your own role in this. How is that going? Technically it’s not an investigation. It’s an inquiry to determine if there is a reason for an investigation. [Editor’s note: The inquiry subsequently reported that it had found no credible evidence that Mann had suppressed or falsified data.]

Do you think you and your colleagues did anything wrong? There’s nothing in any of these e-mails that demonstrates any inappropriate behavior on my part. There are a few things that a certain colleague said that I wouldn’t have said and I can’t necessarily condone, although I can say that they were under a huge amount of pressure. They were attacked by FOIA [Freedom of Information Act] demands. A colleague of mine, Phil Jones, had as many as 40 FOIA demands—frivolous demands—made against him over a single weekend. Frankly, he showed some poor judgment, and there are things I said that I would phrase differently, obviously, if I were saying them in public. But there’s nothing in any of these e-mails, despite the claims of those attacking us, that indicate any sort of conspiracy among climate change researchers to commit fraud, that indicate any destruction of data.

What about the references to “cleaning up” data? Does that amount to destruction? No. In some cases there’s been intentional misrepresentation of what people were talking about in the e-mail exchanges. Nature had an editorial [December 3, 2009] where they basically came out and said that the attackers of climate change had misrepresented two statements. One was about a “trick,” which was simply a reference to a clever mathematical approach to a problem, the way scientists use the term trick: “Here’s the trick to solving that problem,” or “trick of the trade,” and so on. And then conflating that with an unfortunately poorly worded phrase where Phil Jones refers to hiding a decline in temperatures. Much hay has been made of that. But these are internal discussions among scientists who understand the lingo and understand what it means and understand the context. And it’s extremely easy for those looking to make mischief to take single words and phrases out of context.

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 Naturea 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.

If Phil Jones was being inundated by requests for data, why didn’t he just post everything on the Web for all to see? It is very much my practice and the practice of all the scientists I know, at least now, under the sort of criticisms that were made 10 years ago about data archiving policies, to make available every scrap of data that we use in our studies that we are legally permitted to make available. With the Climatic Research Unit’s situation, what you have here is much [less] nefarious than it sounds. The Climatic Research Unit had legal agreements with certain countries that allowed them to use thermometer measurements, but they were legally bound not to distribute the data. The FOIA requests were demands for them to release those data, which they were legally bound not to release. The requests were disingenuous, and they were denied.

But all the rest of the data were released? Yeah. The irony is that the data that they weren’t releasing made no difference to the results.

The National Academy of Sciences supported the key point of your hockey stick calculation, which showed higher temperatures in the 20th century than in the previous thousand years, but others criticized you for not releasing the information behind it. Is all that data now in the public domain? It is. And it was released as soon as we were allowed to do so. I don’t produce any data myself. I just make use of other people’s data. Often scientists in a purely collegial spirit will make available to you data that they haven’t published yet. If you use it, you can’t distribute it. Every single piece of data that we had the right to distribute was available at the time that we published the paper. Once we had permission to publish the smaller number of other records that we hadn’t been able to make available at the time, those were out there.

By May 2000 all of the data were available. All of the claims that our data were not available at the time—by, for example, McIntyre, who’s been leading these attacks—are entirely false.

Many scientists were dismayed by the climate talks in Copenhagen. What was your reaction? There are people in the policy world who would like to see action taken much more quickly, and there are some objective, scientific arguments for that. If we can stabilize CO2 concentrations at 450 parts per million, it gives us probably at least 2 degrees of warming. Some people feel that any more than that and we’ll really start to see the most threatening impacts of climate change. That requires essentially immediate action to slow down emissions and bring them to a peak, then start bringing them down fairly quickly over the next 50 years.

Were you disappointed at the lack of action? I try to approach this from a scientific point of view. My understanding of the science does lead me, personally, to believe that certain policy options are better than others. But the policy in no way influences my science, and I think that’s the way it should be.

Public opinion, at least in this country, has shifted toward the skeptical. It has moved in that direction.

What should scientists do about that? Right now, there’s the largest disconnect that has ever existed between the confidence that we have scientifically and where the public is, at least in the United States. With each passing year, we’ve got more observations. We’ve got a better assessment of what’s happening now in the perspective of what happened in the past, so we can better determine if there are climate trends that are unusual. We have more information about how the system is evolving in response to human impact. We also have supercomputers that are much more powerful. The models we run now produce El Niño events just like they occur in nature. The models are getting better. The science is getting more certain.

Even as the science becomes progressively more certain, the public discourse goes through these cycles. We’ve had the reverse of the perfect storm we had back in 2006. Some people say climate change became too closely associated with a partisan political figure and that polarized the debate. We’ve had a cold winter. We’ve got a bad economy. It’s a bad time to be talking about major changes in our energy economy that some argue could be costly.

The biggest bludgeon the skeptics have is that there is uncertainty in the science. Should you and your colleagues be making more of an effort to quantify that uncertainty? We’ve reached a point now in the interdisciplinary growth of our science where we’ve got climate scientists, who understand the physics of climate and how that translates to uncertainties, working hand in hand with economists who will run the projected impacts through a cost-benefit analysis. The way it plays out is that the small probability of extremely bad things happening incurs huge potential costs, and you want to hedge against those potential catastrophic costs. So when you take uncertainty into account, it actually leads to the decision that we should take action more quickly.

What is the worst-case scenario? Are we talking about the risk of our demise as a species? That’s what scares me, yeah. Now it appears that the antiscience side is in a much better position from a public relations point of view than the scientific community is. I see nothing to change that dynamic. The way our system works, it almost ensures that as an environmental threat grows, there is an institution in place that acts in a way to thwart the attempt by civilization to confront that threat. I fear that it isn’t just a short-term thing. If that is our future, I worry. I have a 4-year-old daughter, and I care about the world that she grows up in.

How do you do research in an environment that is so politicized? It’s difficult. And needless to say, I’m not getting a lot of science done right now. Half my job involves defending myself against attacks.

Has the political polarization had a detrimental effect on progress in climate science? It has. Here’s the most basic example: Scientists like to communicate by e-mail. It’s much more efficient. You can respond whenever you want. Scientists aren’t going to be doing that as much anymore. When you do write an e-mail, you’ll probably take twice as long because you want to make sure that every word can’t be cherry-picked and distorted. You’re second-guessing yourself at every stage and, sure, that slows everything down.

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