One of the phrases I've heard used in praise of Barack Obama is evidence based policy. Nestled in that tiny phrase are so many different ideas that it's difficult to get a handle on what it means. I think the reason I hear it so much now is that Bush's policies were sometimes in outright denial of the evidence.
The core idea is that science tells us many things about how things work. Macroeconomics, as a field, seems to be a core attempt to measure the effect of policy. The lack of respect economists enjoy among other scientists should be a warning sign: The point of basing policy on evidence is to let scientists dictate to politicians about what they should be trying to do, but of how they should be trying to do it.
My perception of economists is that they too often confuse the matter. More often than not, it seems to me (as in the case of the author of The Myth of the Rational Voter, who seems a parody of everything irritating about economists) that economists focus on the accumulation of aggregate wealth, which leads them to endorse policies that are unpopular for reasons that have nothing to do with the wealth of nations.
The role of climate science with respect to the issue of global warming isn't, therefore, to say "Stop! No! Bad!" as much as "If you don't cut carbon emissions sharply, the following things will happen." Having a rational evidence-based debate on policy means weighing the very clear alternatives: Short term higher economic growth against serious ecological impacts and major long-term economic problems, especially for coastal and tropical areas.
When the alternatives are that dramatic, it suddenly behooves the opposition to deny the facts. Abstinence-only "education" leads to higher pregnancy rates; that's a fact. Is it one that supporters of abstinence-only education believe? I doubt it. President Bush seemed to think that reducing teen pregnancy rates and STD infection rates was a desirable social goal, and I have little doubt that the vast majority of voters and politicians agree.
And so, while it is not the job of the economist to say whether full employment is a more valuable goal than 8% annual GDP growth, or whether execution is more or less morally justifiable than the death penalty, neither is it the job of the politician to determine if execution is an effective deterrant, or if girls perform better in mathematics in gender-segregated environments.
One of the things I terribly dislike about this nation is that there are certain facts we are simply not supposed to speak of, certain facts that are too sensitive for politicians to speak aloud in public. There is no such thing as clean coal, not in the here and now, for every kilo of coal burned adds a kilo of carbon to the atmosphere, and the ability to bury that carbon dioxide is well beyond practical.
It's even worse than burning oil, for every kilo of long-chain hydrocarbon burned adds only 0.86 kilos of carbon to the air, every kilo of methane a mere 0.75 kilos. For reference, methane puts out half again as much energy per kilogram, slightly more than doubling the ratio of energy output to carbon output.
For the purpose of the carbon load on the atmosphere, or indeed for the purpose of limiting pollution output, coal is the worst possible fuel in the world to burn. Barack Obama wouldn't say it; Hillary Clinton wouldn't say it; John McCain wouldn't say it. But that's a fact; it's a fact that is as hard and cold as the fact that the polar ice cap will disappear if we keep burning all that coal.
The next time I see a television playing or blog rolling or columnist writing that they don't want to reduce emissions, I want to see them say "because I don't give a **** about the polar bears or Micronesia or the oceans turning to acid, I want to have prosperity in the now while I'm still alive and consuming." I don't want to see them say "because global warming isn't proven," because by golly, that's something that climate scientists are pretty sure about. And they know a lot more than you do, op-ed guy...