Wednesday, April 03, 2013

Warming Wednesdays: what I learned about climate from Nate Silver

The New York Times' resident statistical whiz kept me on an even keel during the run up to the Presidential election: his calculations always gave some advantage to Barack Obama even at the candidate's lowest ebb after the first debate. I wasn't really paying much attention, having my own campaign to work on, but Nate Silver's predictions confirmed the little I could glean from my other observations.

Nate Silver has published a book, The Signal and the Noise: Why So Many Predictions Fail -- but Some Don't, that I can heartily recommend to anyone who wants to evaluate the many predictions we encounter around us and that we make ourselves. It's an argument for utilizing Bayesian probability, an application of mathematical logic, in how we think about the world; if that sounds forbidding, just let me say that Silver's book is not difficult at all. He's a sharp observer of multiple subcultures, including sports, gambling, weather forecasting, economics, and earthquake science. In short, this book is fun and I thought a convincing argument in favor of a mode of prediction that might improve our understandings.

In particular Silver puts the arguments about the reality of climate change in a context I found slightly different than I'd understood. There are people for whom not believing in the climate conclusions of mainstream science is a good gig (sponsored usually by the fossil fuel industry) or who thrive on pure contrarianism, so it possible to say that "not all scientists" agree that global warming is real. But it is possible to discern which climate assertions win wide agreement and which are open to appropriate scientific questions.
… climate scientists are in much broader agreement about some parts of the debate than others. A survey of climate scientists conducted in 2008 found that almost all (94 percent) were agreed that climate change is occurring now, and 84 percent were persuaded that it was the result of human activity. But there was much less agreement about the accuracy of climate computer models. The scientists held mixed views about the ability of these models to predict global temperatures, and generally skeptical ones about their capacity to model other potential effects of climate change. Just 19 percent, for instance, thought they did a good job of modeling what sea-rise levels will look like fifty years hence. …
It is useful to the mere interested observer of scientific argument to have to parameters of consensus laid out so clearly.

The fact that some issues still need more data points and more sophisticated models in order to generate predictions that command overwhelming assent would not be a problem if climate change were merely a puzzle for scientists. But the scientific mode of knowledge has wandered into a political minefield where its conventions don't fit social needs.
The fundamental dilemma faced by climatologists is that global warming is a long term problem that might require a near-term solution. Because carbon dioxide remains in the atmosphere for so long, decisions that we make about it today will affect the lives of future generations. In a perfectly rational and benevolent world, this might not be so worrying. But our political and cultural institutions are not so well-devised to handle these problems …

Michael Mann, who is director of the Earth System Science Center at Penn State University,
"We're in a street fight with these people," he told me, referring to [one characterization of climate change skeptics]. 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. In a society accustomed to overconfident forecasters who mistake the confidence they express in a forecast for its veracity, expressions of uncertainty are not seen as a winning strategy by either side.

"Where you have to draw the line is to be very clear about where the uncertainties are, but to not have our statements be so laden in uncertainty that no one even listens to what we're saying," Mann told me. "It would be irresponsible for us as a community to not be speaking out. There are others who are happy to fill the void. And they're going to fill the void with disinformation."
Responsible prediction is hard; Nate Silver at least makes its contours more accessible in this book.

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