If you want to feel optimistic about the possibilities for climate action in the wake of the election, here are the tea leaves to read.

Nineteen percent of voters were beneath the age of 30, something no one in D.C. expected. Young voter translates into “not primarily obsessed with my Medicare, hence able to think about the world.” So the pros know this is the demographic that cares about climate.

Meanwhile, 41 percent of voters told exit pollers that the response to Sandy was an important factor in their vote. The climate silence of the campaign was broken by … the climate. And then Obama got about the biggest cheer of his victory speech with a reference to wanting to save America from the destructive power of a warming planet.

Of course, if you want to feel pessimistic, there’s always: Sandy, which demonstrated we’ve waited a long time to get started. Not to mention the warmest year in American history, now concluding. Not to mention our epic drought. Or the small fact that this was the year we broke the Arctic.

The point is, since we’re running out of spare presidential terms in which to turn things around, we need to seize the moment for big, transformative change.

The first, best test will the Keystone pipeline. If Obama nerves himself up to defy the fossil fuel industry and block it, it will be the first time he’s helped to keep some carbon in the ground. This is the guy who, in his first term, opened up the Powder River Basin to Peabody, and the Arctic to Shell.

If Keystone gets built, it will carry exactly as much carbon as the president’s auto mileage standards will save. It will literally negate the one really good thing he’s done.

But say it gets blocked — say the grassroots wing of the environmental movement sees it can trust the president. Imagine the combined power of the D.C. enviros and the folks on the ground, finally building the joint movement that can amass the power necessary to, say, put a price on carbon.

They don’t call it Keystone for nothing.

This post is part of our November 2012 theme: Post-election hangover — whither the climate?