Earlier this year, while doing this piece on John McCain's environmental record, I talked briefly with his policy guru, Doug Holtz-Eakin, who noted that McCain's approach to climate policy would be more "conservative" than Clinton's or Obama's, insofar as he'd push for a cap-and-trade bill but not a whole lot more besides. I figured this was worth hashing out further, especially in light of this recent interview that Holtz-Eakin did with E&E, where he emphasized the point.
In a nutshell, McCain's camp argues that all you basically need to do to cut carbon emissions drastically is to put a price on carbon—by, say, setting an economy-wide limit on greenhouse gases and then allowing companies to buy and sell pollution credits. Once you do that, the market will figure out how to meet the new CO2 targets on its own, and the government doesn't need to "help" by passing stuff like fuel-economy standards, or efficiency codes for buildings, or what have you. (Holtz-Eakin added that there wasn't a "bright line" here and McCain wasn't opposed to all regulations, but agreed that there was a basic philosophical difference.)
Anyway, that argument sounds fairly sensible, but there are a couple of decent objections to it. Obama's energy adviser, Jason Grumet, has pointed out that if all you have is a cap-and-trade bill, and you wanted to reduce emissions 80 percent by 2050, say, the price of carbon would have to be set at something like $150/ton—which could wreak a fair bit of economic havoc. A more reasonable price might be something like $40/ton, but that probably wouldn't be enough to induce major changes in, say, the transportation or agricultural sectors, so you'd need to couple a cap-and-trade with CAFE standards, land-use policies, funding for public transit, and so forth.
Another piece of this is that, as the New York Times explores today, a number of experts are questioning whether the technology even exists (or will exist in the near-future) to allow industries to make the necessary emissions cuts in short order. So there's a very good case to be made that the government should be pushing policies to spur alternative energy sources (whether that's funding R&D, or mandating that utilities get a certain amount of their energy from renewables, or what have you). McCain mostly shies away from that, save for nuclear power. Now, I realize there are lots of nuclear fans out there, but it's worth noting that even a major nuclear renaissance in the United States—say, a staggering 200 new plants by mid-century—would still only provide for a fraction of energy use in the country. So it certainly can't be the only solution for weaning the country off fossil fuels.
Anyway, there are other differences between McCain and the two Dems on climate policy (the debate over auctioning off pollution credits in a cap-and-trade system is the biggest one), but this is one big one. It'd be nice to think that these distinctions will come out and get debated in the general-election campaign, rather than the press just assuming that both candidates basically have similar views, but who knows...