President Obama makes his inaugural address in Washington on Jan. 21  Vice President Joe Biden made a surprise appearance on Jan. 20 at the Green Ball, an inaugural event for environmental groups—and his message to the crowd couldn’t have been more welcome:  I’ll tell you what my green dream is: that we finally face up to climate change…I don’t intend on ending this four years without getting an awful lot more done. Keep the faith.  Environmentalists—who’d grumbled during the campaign about the absence of climate change from President Obama’s rhetoric—didn’t have to wait long to see their faith rewarded. During his inaugural address on Jan. 21, Obama spoke with surprising clarity and urgency about the need to fight global warming:  We, the people, still believe that our obligations as Americans are not just to ourselves, but to all posterity. We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations.  Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires, and crippling drought, and more powerful storms. The path towards sustainable energy sources will be long and sometimes difficult. But American cannot resist this transition. We must lead it.  Those were bold words—and words that lifted the hearts of the environmentalists in the audience on the National Mall in Washington and watching the speech around the country. But climate change—especially so far for President Obama—has always been a subject that’s easier to talk about than do anything about. As he begins his second term faced with a financial crisis and an intransigent Republican opposition, can Obama actually do something about global warming?  First a quick retrospective. That uneasiness that many environmentalists felt towards the President as he campaigned for reelection this past summer wasn’t just about the disappearance of climate change as an issue. It was also due to the sense that Obama had largely failed to do much of anything on global warming during his first four years in office.  That’s not an entirely fair charge. The massive stimulus plan passed in the early days of the President’s first term contained $90 billion for green technologies—and not coincidentally, wind, solar and other green sources of energy are in better shape now than they’ve ever been before. Obama pushed through a major tightening of automobile fuel efficiency standards, a move that will cut foreign oil imports and cut carbon. The Environmental Protection Agency (EPA) began tightening air pollution standards that will reduce the use of coal, and U.S. carbon emissions actually fell on Obama’s watch—though that has more to do with the increase of cleaner natural gas than anything purposeful the President did.  But on the campaign trail Obama had promised to pass a comprehensive bill to cap U.S. carbon emissions, and that effort ultimately met with failure. Exactly why has been a subject of discussion over the past week, thanks to a pair of papers—one from Peter Bartosiewicz and Marissa Miley, and from Theresa Skocpol—that dug deep into the legislative fight. In a nutshell, climate advocates followed a bad legislative strategy, one that focused on allying with business interests even as the increasingly radical Republican party was less interested in listening to those large corporations. That sense that big green groups were cutting deals with major polluters like Duke Energy—a charter member of the U.S. Climate Action Partnership—in turn cut into Democratic and grassroots green enthusiasm for the fight.  It’s a cogent and deeply report analysis, albeit one that my colleague Michael Grunwald took issue with last week, noting that the intransigence of the Republican party would likely have nullified even stronger outside pressure from greens and Democrats. Personally, while I think environmentalists could have handled the strategy of the cap-and-trade fight better—and Obama could have taken a stronger hand—I’m doubtful their’s was a winnable fight. The Democratic divisions on cap-and-trade—where a number of prominent Midwestern senators hail from coal-heavy states—are much deeper than they were on health care reform, which also had the advantage of decades of advance work. Add in the fact that greens were trying to pass a bill that would raise energy costs during one of the worst economic downturns in recent U.S. history, as well as post-crash skepticism of any kind of new financial trading mechanism, and I’m impressed cap and trade came as close to passage as it did.  Unfortunately for environmentalists—and you know, people who care about the future of their children—none of these factors have changed as Obama begins his second term. A comprehensive climate bill, barring some kind of miracle, isn’t going to happen. So what can the President do to ensure his actions match his words on global warming?  Over at the Washington Post‘s Wonkblog, Brad Plumer has a nice rundown of the options that are available to Obama. Those include:  As you can see, that’s… not a long list. The most significant item is EPA regulatory power, but Obama has always maintained that he’d prefer not to use it, and right now the EPA has no chief. (Administrator Lisa Jackson announced her resignation late last year.) Any effort to slap meaningful regulations on greenhouse gases would lead to howls from Republicans, and likely legal action from utilities. Obama could decide to permanently cancel the Keystone XL oil sands pipeline, but while that would earn him serious cred from green groups, I’m doubtful that it would do much to ultimately derail oil sands development and carbon emissions in Canada.  (I’m not even going into the fact that the most significant carbon reductions will need to be made not so much in the U.S. as in large developing nations like China—and President Obama has even less sway with the Politburo than he does with the Republican-controlled House, though the former might be less of a headache.)  All of which means that the President faces a major challenge if he’s going to match his words on global warming with appropriate action. The bitter irony is that four years from now, President Obama’s supposed failure of a first term may represent his peak for climate action.  Bryan Walsh is a senior editor at TIME. Find him on Twitter at @bryanrwalsh. 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After a disappointing first term, environmentalists are hoping for action on climate change from President Obama—and he promised to deliver. But what can he actually do?