Blog Archive

Monday, September 24, 2012

Michael Mann: FiveThirtyEight: The Number of Things Nate Silver Gets Wrong About Climate Change

by Michael E. Mann, Huffington Post, September 24, 2012

If you're a science or math geek like me, you can't help but like Nate Silver. He's the fellow nerd who made good. His site is a must for any serious polling buff, and he regularly graces the leading talk shows with his insightful if wonky commentary. So you can imagine how excited I was a year ago when Nate's assistant contacted me, indicating that he wanted to come to State College, PA -- the "happy valley" -- to interview me for his new book on "forecasting and prediction."

Nate, I was told, was working on a chapter about global warming. He sought me out because he felt my expertise would make me an "excellent guide to the history of climate modeling." He also expressed interest in my own upcoming (since published) book The Hockey Stick and the Climate Wars which details my experiences at the center of the climate change debate. Needless to say, I was very much looking forward to the meeting.

And so it was on a crisp early November day that Nate arrived at my office in the Walker Building of the Penn State campus. We exchanged pleasantries and proceeded to engage in a vigorous, in-depth discussion of everything from climate models and global warming to the role of scientific uncertainty, and the campaign by industry front groups to discredit climate science (something that is the focus of my own book). As I saw Nate off, I insisted he sample the Penn State Creamery's famous ice cream before leaving town. I tweeted excitedly about my meeting with him, and by the end of the day Nate had even added me to his relatively short list of twitter followees. Certain our discussion had been productive and informative, I awaited Nate's book with great anticipation.

And so I was rather crestfallen earlier this summer when I finally got a peek at a review copy of The Signal and the Noise: Why So Many Predictions Fail -- but Some Don't. It's not that Nate revealed himself to be a climate change denier; He accepts that human-caused climate change is real, and that it represents a challenge and potential threat. But he falls victim to a fallacy that has become all too common among those who view the issue through the prism of economics rather than science. Nate conflates problems of prediction in the realm of human behavior -- where there are no fundamental governing "laws" and any "predictions" are potentially laden with subjective and untestable assumptions -- with problems such as climate change, which are governed by laws of physics, like the greenhouse effect, that are true whether or not you choose to believe them.

Nate devotes far too much space to the highly questionable claims of a University of Pennsylvania marketing Professor named J. Scott Armstrong. Armstrong made a name for himself in denialist circles back in 2007 by denouncing climate models as having no predictive value at all. Armstrong's arguments were fundamentally flawed, belied by a large body of primary scientific literature -- with which Armstrong was apparently unfamiliar -- demonstrating that climate model projections clearly do in fact out-perform naive predictions which ignore the effect of increasing greenhouse gas concentrations. As discussed in detail by my co-founder, NASA scientist Gavin Schmidt, Armstrong simply didn't understand the science well enough to properly interpret, let alone, assess, the predictive skill of climate model predictions.

That Nate would parrot Armstrong's flawed arguments is a major disappointment, especially because there are some obvious red flags that even the most cursory research should have turned up. A simple check of either SourceWatch or fossil fuel industry watchdog ExxonSecrets, reveals that Armstrong is a well-known climate change denier with close ties to fossil fuel industry front groups like the Heartland Institute, which earlier this year campaigned to compare people who accept the reality of climate change to the Unabomber, and secretly planned to infiltrate elementary schools across the country with industry-funded climate change denial propaganda. I suspect that Nate's failing here arises from a sort of cultural bias. There is a whole community of pundits with origins in economics and marketing who seem more than happy to dismiss the laws of physics when they conflict with their philosophy of an unregulated market. Nate may not share that philosophy, but he was educated by those who do.

Nate Silver was trained in the Chicago School of Economics, famously characterized by its philosophy of free market fundamentalism. In addition to courses from Milton Friedman, Nate might very well have taken a course from University of Chicago economist Steven Levitt, known largely for his provocative 2005 book Freakonomics and its even more audacious 2009 sequel Super Freakonomics -- a book that, perhaps better than any other, serves as a cautionary tale of the dangers that lurk when academics attempt to draw sweeping conclusions in fields well outside their area of training. In Super Freakonomics as you might guess, Levitt drew questionable conclusions about climate change and related energy issues based on an extrapolation of principles of economics way, way, way, outside their domain of applicability. Even some very basic physics calculations, for example, reveal that his dismissal of solar energy as a viable alternative to fossil fuel energy in combating climate change because of possible waste heat is total nonsense. Ray Pierrehumbert, a chaired professor himself at the University of Chicago in the Department of Geosciences, pointed this and other serious errors out to Levitt in an open letter that concluded with a campus map showing how easy it would have been for Levitt to walk over to his office to discuss his ideas and, presumably, avoid the serious pitfalls that ended up undermining much of what he ended up saying in his book about climate change and energy policy.

Unlike Levitt, Nate did talk to the scientists (I know. I'm one of them!). But he didn't listen quite as carefully as he should have. When it came to areas like climate change well outside his own expertise, he to some extent fell into the same "one trick pony" trap that was the downfall of Levitt (and arguably others like Malcolm Gladwell in The Tipping Point). That is, he repeatedly invokes the alluring, but fundamentally unsound, principle that simple ideas about forecasting and prediction from one field, like economics, can readily be appropriated and applied to completely different fields, without a solid grounding in the principles, assumptions, and methods of those fields. It just doesn't work that way (though Nate, to his credit, does at least allude to that in his discussion of Armstrong's evaluation of climate forecasts).

As a result, Nate's chapter on climate change (Chapter 12: "A Climate of Healthy Skepticism") is marred by straw man claims that don't stand up to scrutiny. These include the assertion that (a) climate scientist James Hansen's famous 1988 predictions overestimated global warming (they didn't), that (b) "the Intergovernmental Panel on Climate Change (IPCC) settles on just one forecast that is endorsed by the entire group" (pure nonsense -- even the most casual reading of the IPCC reports reveals that great care taken to emphasize the non-trivial spread among model predictions, and to denote regions where there is substantial disagreement between the projections from different models), and that (c) "relatively little is understood" about the El Nino cycle (here I imagine that Nate might have misinterpreted our own discussion about the matter; I explained in our discussion that there are still open questions about how climate change will influence the El Nino phenomenon -- but that hardly means that we know "relatively little" about the phenomenon itself! In fact, we know quite a bit about it). Finally, and perhaps most troubling (d) while Nate's chapter title explicitly acknowledges the importance of distinguishing "signal" from "noise" and Nate does gives this topic some lip service, he repeatedly falls victim to the fallacy that tracking year-to-year fluctuations in temperature (the noise) can tell us something about predictions of global warming trends (the signal). They can't -- they really can't.

Nate's view of uncertainty, and its implications for climate model predictions, is particularly misguided. He asserts that the projections of the IPCC forecasts have been "too aggressive," but that is simply wrong. It neglects that in many cases, e.g., as regards the alarming rate of Arctic sea ice decline (we saw a new record low set just weeks ago), the climate models have been far too cautious; We are decades ahead of schedule relative to what the models predicted. Uncertainty cuts both ways, and in many respects -- be it the rapid decline in Arctic sea ice, or the melting of the ice sheets -- it is cutting against us. Uncertainty, as many economists recognize, is thus a reason for action, not inaction! I'm surprised someone as sharp as Nate just doesn't appear to get that.

Nate also takes some unnecessary cheap shots. In what has now become a rite of passage for those looking to establish their "honest broker" bona fides in the climate change debate, Nate makes the requisite "punch the hippie" accusation that Al Gore exaggerated the science of climate change in An Inconvenient Truth (a team of climate scientists reviewed the movie for accuracy and found that by-and-large Gore got the science right). He characterizes climate scientist Gavin Schmidt as a "sarcastic" individual who is unwilling to put his money where his mouth is by betting his personal savings on his climate model predictions (this felt to me reminiscent of Mitt Romney's widely mocked $10,000 bet challenge to Rick Perry). And while I do appreciate some of the nice things Nate says in the book about me personally (e.g., "Mann is exceptionally thoughtful about the science behind global warming"), he at the same time deeply misrepresents our discussion on several counts.
I had emphasized the importance of distinguishing the true uncertainties in climate science (and there are plenty, e.g., the influence of warming on hurricanes, how the El Nino phenomenon might be affected, or how regional patterns of rainfall may change) from the manufactured uncertainties and myths typically promoted by climate change deniers and contrarians (e.g., "how come there has been no warming since 1998?" -- the answer is that, of course, there has been). I stressed how important it is, when scientists communicate to the public, to make clear that while there are many details that are still uncertain, the big picture (that humans are warming the planet and changing the climate, and that far larger and potentially more dangerous changes loom in our future if we don't act) is not.

Nate cherry-picks a single sound bite ("our statements [should not be] so laden in uncertainty that no one even listens") to once again reinforce the false narrative that scientists are understating uncertainty. The point I was actually making was that we cannot spend so much time talking about what we don't know, that we don't end up telling the public what we do know. That, as Nate correctly quotes me, "would be irresponsible." Nate states that "the more dramatic [climate scientists'] claims, the more likely they [are] be quoted...," seemingly implying that scientists have a motivation to overstate the science. He ignores the fact that those scientists willing to feed the false "scientists are exaggerating" narrative are the true darlings of the "balance" over "objectivity" school of news reporting -- a school of thought that Nate sadly seems to have subscribed to.

Most disappointing to me of all was the false equivalence that Nate draws between the scientific community's efforts to fight back against intentional distortions and attacks by an industry-funded attack machine, and the efforts of that attack machine itself. He characterizes this simply as a battle between "consensus" scientists and "skeptical" individuals, as if we're talking about two worthy adversaries in a battle. This framing is flawed on multiple levels, not the least of which is that those he calls "skeptics" are in fact typically no such thing. There is a difference between honest skepticism -- something that is not only valuable but necessary for the progress of science -- and pseudo-skepticism, i.e., denialism posing as "skepticism" for the sake of obscuring, rather than clarifying, what is known.

Nate deeply mischaracterizes an editorial published by the prestigious and staid journal Nature (whose sentiments are echoed in my book The Hockey Stick and the Climate Wars) warning scientists that they "must acknowledge that they are in a street fight, and that their relationship with the media really matters." Nate grossly mischaracterizes the quote, claiming that "the long-term goal of the street fight is to persuade the public and policy makers about the urgency (or lack thereof) of action to combat climate change." Nate makes it sound like the "street fight" was of the scientists choosing, completely turning on its head what Nature was actually talking about: scientists finding a better way to defend science from cynical attacks whose sole aim is to confuse the public about what we actually do know about climate change (and therefore forestall any efforts to deal with it).

I could detail the numerous other problems with the chapter (and no -- there aren't really 538 of them; I confess to having taken some "poetic license" with the title of this commentary). But the real point is that this book was a lost opportunity when it comes to the topic of climate change. Nate could have applied his considerable acumen and insight to shed light on this important topic. But the result was instead a very mixed bag of otherwise useful commentary marred by needless misconceptions and inappropriately laundered denialist memes.

Don't get me wrong. I'm still a FON (Fan Of Nate). I will continue to follow his thoughtful commentary on all matters of politics and polling. But when he makes claims about other topics, like climate change, I think I'll be a lot more skeptical. Skepticism -- real skepticism -- is, after all -- a good thing.

No comments: