The recession's here. Let's tax carbon! The first hundred days of any presidency rarely go off as planned, but, for now, Barack Obama seems to know what's at the top of his to-do list. In late October, he told Time's Joe Klein that "a new energy economy" would "be my number-one priority when I get into office." But then, as if to cut off a lurking objection, Obama quickly tacked on a qualifier: "assuming, obviously, that we have done enough to just stabilize the immediate economic situation." The caveat seemed to nod at a nascent conventional wisdom: Now that the United States is staring down the barrel of a nasty recession, many Washington types wonder if Obama will have to tear up that to-do list and rein in his ambitious climate and energy proposals. True, not all of Obama's green ideas are controversial: You can't pick up a newspaper op-ed page these days without seeing yet another economist argue that government spending on clean energy and eco-friendly infrastructure could provide the Keynesian boost necessary to haul the economy out of its mire. But the linchpin of Obama's energy platform wasn't new spending; it was an economy- wide cap on carbon-dioxide emissions, in which a decreasing number of tradeable pollution permits would be auctioned off each year, so as to ratchet down greenhouse gases and help avert drastic global warming. Energy experts tend to agree that it's not enough for the government to fund alternative-energy sources; the only way to usher in the "new energy economy" Obama envisions is to make it costlier to burn fossil fuels. But that's the catch: Since Obama's cap-and-trade proposal would essentially act as a tax and increase the price of oil, gas, and coal, he downplayed this aspect of his plan on the trail--and it's the one idea that now looks most vulnerable. The queasiness is understandable. On the surface, it really doesn't sound like a hot idea to impose broad new regulations on a struggling economy. In this case, though, the fear is misguided. Global warming is urgent enough that the next administration will need to go all-out on the issue, passing not just a green stimulus package but especially a cap on carbon. And, not only is the recession a poor excuse to hold back, it may even be all the more reason to act....