The last few weeks have been a rhetorical high-water mark for climate concern. The trouble is, they’ve also been a high-water mark for … water. Before you read the rest of this short essay, you might want to take 46 seconds to watch this video of a “king tide” path of destruction across the Marshall Islands in the Pacific last week. This is just the kind of thing starting to happen across the planet.

Watching it helps you understand just how right Secretary of State John Kerry was when he called global warming “the world’s most fearsome weapon of mass destruction.” That’s the sharpest language any high-ranking official has ever used about climate.

Not to be outdone, Kerry’s former Senate colleagues staged an all-night teach-in on the chamber floor Monday, with 30 Democrats one after another explaining the peril the planet faced. Harry Reid: “It’s a question of our survival.” Tim Kaine: “We need to take any action that gets us from dirty to less dirty.” Ed Markey, channeling one Dr Seuss: “Unless someone like you cares a whole awful lot, nothing is going to get better. It’s not.”

All of this counts as a pretty striking change of tone. President Obama campaigned across the heartland of America in 2012 without ever mentioning climate change—even though the year smashed the all-time high temperature record for the country, and the Midwest drought was the most severe since the Dust Bowl. Now even the president sometimes talks about climate change, and when he does it’s in stirring terms. In January’s State of the Union address, he said we’d have to account for our actions to “our children’s children.” Such rhetoric is part of the education our society has to go through before it’s ready to act.

The sadness, though, is how much time has already passed. This is the kind of talk that would have made great sense a quarter century ago when scientists first explained what global warming was going to do to the planet. In the intervening 25 years, humans have poured more carbon into the atmosphere than in all the time before, taking us past the point where we can “stop” global warming. Now we can, at best, “stop it from getting worse.”

Doing even that, of course, is going to require more than talk. It’s going to require taking every possible action one can think of. At home, yes, that means changing light bulbs (is there someone left out there who hasn’t changed theirs yet?). But the real change is going to have to come in Washington.

And given the GOP’s stance (the only Republican senator who showed up for Monday night’s marathon was Oklahoma’s James Inhofe, on hand to poke fun at the Democrats), there’s not much even stalwart senators like Bernie Sanders or Sheldon Whitehouse or Barbara Boxer can really accomplish. Even the president has limited options: national climate legislation is not a real prospect with John Boehner and Mitch McConnell in the way.

But there are places where Obama and Kerry can go beyond words, and chief among them is stopping the Keystone Pipeline. This has turned into the hardest-fought environmental battle in a generation, bringing more Americans into the streets (and the jails) and generating more public comments than almost any green issue since the first Earth Day. And that’s because everyone knows that it’s Obama’s chance to actually show he means what he says. Not to enact some regulation that may pay off 10 or 20 years down the road, but to stand up right now to the fossil fuel industry.

The math couldn’t be simpler. The pipeline will help liberate tar sands oil from the Canadian province of Alberta—a province that holds one of the world’s biggest deposits of carbon, enough to make even slowing climate change impractical. But simple math doesn’t always work in Washington—you have to factor in the campaign contributions, the lobbying money. As a result, the conventional wisdom has always been that Keystone will be built.

But the conventional wisdom needs to change. That’s what that video of high tide obliterating Pacific homes makes clear. That’s what you know when you see the latest chart of melting Arctic sea ice, once more on a record pace.

One would like to think, listening to Kerry, that his State Department will recommend Keystone is not in the national interest. One would like to think, listening to Obama, that he’ll do the right thing. If they block Keystone, they become the first world leaders to stop a big project because of its effect on climate; they get a little bit of leverage to reopen the international negotiations that ran aground at Copenhagen way back in 2009.

But for the moment it’s still all words. And high tides and melting ice.

Bill McKibben is Schumann Distinguished Scholar in Environmental Studies at Middlebury College, and the founder of the global climate campaign 350.org