Standing before University of California at Irvine’s graduating class this June, Barack Obama did something no U.S. president has done before: He stood up for climate science. Not only did the president make a strong case for taking immediate action to mitigate global warming, he delivered a withering critique of climate deniers, whom he likened to those who would suggest the moon was “made of cheese.”

Even more outrageous, writes journalist Mark Hertsgaard, is a comment Obama made on Showtime’s climate change documentary series, “Years of Living Dangerously.” Discussing the need to limit warming to the internationally agreed-upon limit of 2 degrees Celsius, and the challenge presented by the world’s remaining fossil fuel reserves, the president told New York Times columnist Thomas Friedman: “We’re not going to be able to burn it all.” That small, mysteriously uncommented-upon comment, Hertsgaard says, represents a significant leap in Obama’s approach to climate change — one that radically contradicts his own, “all of the above” energy policy.

Is the president finally living up to the campaign promises he made back in 2008? The night he won the Democratic nomination, the then-junior senator proclaimed, would go down as “the moment when the rise of the oceans began to slow.” A “planet in peril,” he said, would be one of his top three priorities — another presidential first.

Newly elected, Obama made a few significant efforts toward that goal. Then, Hertsgaard writes in the July issue of Harper’s [paywalled], he appeared to drop the issue completely. Worse still was his energy policy, meant to appease the interests of Big Oil: “Instead of listening to the scientists,” as one critic put it, “he has embraced this balancing act that tries to please everybody” and in the process failed to address climate change in a meaningful way.

In his second term, the president appears to be back on track, as determined as ever to fight climate change. Yet a year after the 2013 speech in which he laid out his ambitious agenda for bypassing Congress to achieve those goals, it remains unclear how much Obama will be able to accomplish this late in the game — and how his efforts will be remembered in the far-off, and far warmer, future. White House advisers Hertsgaard spoke with, including John Podesta and Carol Browner, don’t sound too confident. His time’s almost up, after all, and the obstacles — political, economic, technical — remain formidable.

Salon spoke with Hertsgaard about Obama’s late-game climate push, and about his call for “vigorous, organized, and sustained popular pressure and protest” to get the president to keep his promises. Our conversation, lightly edited for length and clarity, is below.

As someone who has been covering climate change for so many years, how would you characterize the overall political mood right now? We have this president doing more than any other previous president has, but we have this very vehement backlash from the right against any climate action.

Well, it’s true that Obama has done more than any other previous president. But that is a very, very low bar. The problem in U.S. politics on climate change has been long-standing. It actually goes back to something I wrote about briefly in the Harper’s article, and more extensively in a previous article for Businessweek magazine that was published at the end of February. And that article made the argument that the United States is essentially a petrol state. We are an OPEC nation in everything but name, and oil in particular has saturated our political economy for over a century. The big oil companies have been working hand in glove since the 1920s with the State Department, with the White House, with the CIA. And since the 1940s and 1950s, the fact that the U.S. had its own oil resources, and therefore an abundant relatively cheap supply of oil, had the most profound consequences for our economy. It’s what enabled us to have the big postwar economic boom that came out of building all of those suburbs and all of those freeways that connected them and the whole fast-food drive-in culture that grew up in this country during the ’40s, ‘50 and ’60s. And whatever you think about that from a cultural/environmental standpoint, the economic implications of that were huge.

So those kinds of factors are very, very deep in American politics and so much of America’s, and in particular Washington, D.C.; the federal government’s response to climate change has been shaped by that. For more than 20 years now, the federal government has dragged its feet on facing the climate crisis directly and certainly on doing anything about it. The denial machine started in the United States. The efforts to derail and delay any kind of meaningful federal action, they go back 20 years. And that’s because Big Oil has always had, essentially, a veto power over what the federal government does, both because of its economic might — I mean, we’re talking about the richest business enterprise in human history — and all the political muscle that comes from that. That historical background, I think, is essential to understanding not just the backlash that Obama is facing on climate action, but the generally very poor record that the United States has had on climate action.

Of course, you need leadership in Washington, and Barack Obama, I think, genuinely gets it on climate change. He understands the science and I think he wants to do the right thing. But it’s never easy for the president of the United States to say no to Big Oil. I know a lot of Obama’s erstwhile supporters and certainly many of the readers at Salon, like liberals and progressives in general, have been very disappointed by this president on climate change, among other issues. And while I certainly understand that point of view and share it to some extent, I think it’s important to recognize the institutional constraints that operate against any U.S. president. It’s just not easy to say no to Big Oil when you are the head of a petrol state. Tell me the last time you saw a Saudi sheik or a Nigerian or Venezuelan strongman say no to their oil industry.

In another Businessweek column last week you called out this astounding quote from Obama: “We’re not going to be able to burn it all.” And as you say, he contradicted his own “all of the above” energy policy. Do you see that as a watershed moment for him or do you think that he was quoting a popular line, that he’s not really going to be able to support that with action?

I think it is a watershed moment. What the president of the United States says matters a great deal. You can see that on a lot of other issues. If the president of the United States, for example, suddenly said, “We do or we don’t believe in a two-state solution to the Israeli-Palestinian conflict,” or “We believe that the government in Iraq should do X, Y, or Z,” that matters, even if U.S. policy is not congruent with that. It’s not a small thing for the president of the United States to say that essentially two-thirds of the fossil fuels needs to remain in the ground, even if his policies are separate from that, because then it opens the question of, “Well, Mr. President… If you understand that why aren’t your policies in line with that?” So I can’t believe that Obama was not aware of what he was saying. From all my reporting he understands the science of climate change pretty well.

What I think was interesting about it as the story unfolds is how much will people hold him to account for that. When I say people I mean in particular, members of Congress, I mean the environmental organizations that I would think should welcome Obama’s statement on this. I’m talking about people like Hank Paulson and Robert Rubin and Tom Steyer and Michael Bloomberg, who released their big study last week, “Risky Business,” talking about the economic dangers of inaction. And last but not least the other diplomats and negotiators from other countries who are going to be trying to create this climate agreement technically in Paris in 2015. But the first talks on that — well, not the first, but the first high-level talks — are happening at the U.N. in September. Surely there will be people at that meeting from other countries saying, “Well, we were very happy to see the president of the United States say this. Now where’s the beef?”

Do you think it could foreshadow more radical policy?

It could. But it’s all a question of how much civil society — international civil society included — responds to this. The president has opened a door there by saying this, by standing up for science. And I think the people should applaud that if we really believe in science and we really understand just how dire the scientific situation is. It’s important for a president to stand up and say, “Yes, the science is correct.” Let’s think back to how few American presidents have done that in recent years. The previous president, George W. Bush, certainly didn’t do that. The president before that, Bill Clinton, despite Al Gore being his vice president, did not stand up for science until he left the Oval Office. Which, again, I would say kind of goes back to that U.S. as an OPEC nation. These guys, like Clinton, he knows perfectly well the science and I think he knew it perfectly well when he was president. But it’s just not that simple to say, “Oh, we’re going to go in another direction.” In fact, the official who made that statement to me about the U.S. as an OPEC nation worked in Bill Clinton’s administration and he ran the intergovernmental agency discussions on climate change as an economist and he talked about how basically the big oil companies were constantly hammering against them on this very basis.

As huge as it is for the president to acknowledge the science and the need for action, you also can’t overstate enough the economic cost of going along with what needs to be done to mitigate climate change. Do you think that the president is ready to have that conversation and be frank about what we may need to sacrifice?

I don’t know about the president’s readiness. But if I were one of his communication advisors I would suggest that he frame that conversation in a little bit different way than that question does, or frankly than the Businessweek graph did. Because yes, those profits, the $28 trillion in carbon that’s in the ground, some of that would have to be sacrificed. But that’s for those particular companies or the holders of that wealth. They would sacrifice that. However, society as a whole, which is what all of us should care about and every democratically elected president should care about, we wouldn’t be sacrificing that wealth because there would be an enormous amount of additional separate wealth created and expanded through going in the direction of non-carbon energy sources. And if I were advising the president that’s certainly what I would suggest [as] the way that he present it. Obama’s already talked about that quite a bit in the past. About how energy efficiency and solar and this and that, all the others, offer terrific alternative prospects.

When you talk about the Clean Air Act you call it the “towering irony of Obama’s presidency,” because he already had a mandate to reduce emissions. Could you explain a little bit more what you mean by that?

That’s such a critical point. And “mandate” is exactly the right word for you to use. The irony in Obama’s case is that he spent the first year of his first term trying to pass the ill-fated cap-and-trade proposal. But, in fact, he had all the authority he needed under the Clean Air Act — not just the authority, but the legal obligation — to deal with this. The Clean Air Act is really one of the most amazing pieces of legislation that’s ever been passed in the United States. Let’s remember that the Clean Air Act and other U.S. laws are the basis for many, many other countries’ environmental laws. And what’s extraordinary about the Clean Air Act is, as I always like to point out, that it uses the verb “shall,” as in “must.” The federal government shall assure that the air is clean for American citizens and — and this is really critical — economic considerations are not supposed to play a role, any role, in how regulators approach that responsibility. And indeed the assumption in the Clean Air Act is that federal regulations should be “technology forcing,” meaning that they should compel businesses to go beyond what they would do on their own and fix the problem regardless of what the economic implications are. That is not indifference, as some on the right would argue, to the economic implications of that. Rather, it’s a vote of confidence in the innovative abilities of American entrepreneurs to come up with solutions. So that Clean Air Act really gave Obama and any other U.S. president — including George W. Bush — the same authority and the same obligation to deal with these problems. So it’s nice that the president has finally come around to recognizing that in his second term. It’s too bad it took him six years to do it.

You also write that the greatest climate victory came from grassroots activists, one, and lowering the demand for coal, second, which also seems pretty ironic to me. These weren’t things that came from any policy decisions.

You know, oftentimes the way we citizens and we in the media approach these questions is through the prism of Washington, D.C., and if it ain’t happening in D.C., we think it ain’t happening. But in fact, as you mentioned, by far the most carbon that was kept out of the ground in the Obama years was because of these grassroots activists. I had done a long investigation of this, and it was really fascinating to see where these activists were winning, because it was not in Berkeley and Cambridge, Massachusetts, and Ann Arbor, and all the sort of granola-eating places in the country. It was in South Dakota and Ohio and even Kentucky and South Carolina and Texas, all these supposedly red states that nevertheless, when you really talk to the people, and you get out of the Washington bubble and all the political assumptions that tend to dominate discussion there, you find out that people across the political spectrum, nobody wants their air to be polluted, everybody wants their kids to be able to breathe clean air.

One of the great examples was the mayor of Dallas, who granted was a Democrat, but still in Texas, and she was one of the people very closely involved in the decision there to block between seven and ten proposed coal plants. And why? Well, it was partly because of pressure from nurses in the American Lung Association saying that this will be bad for our kids, but it was also a very hard-headed business calculation that, “Look, I want the local economy to grow, I want to entice firms to come here, to bring their operations here, and that is not going to happen if we’ve got disgusting, dangerous air for them and their kids to breathe.” And so those kinds of decisions I think give great hope to people who say, oh there’s no hope, there’s political deadlock, the Republicans this, the Republicans that. There is truth to that, of course, if you confine your analysis to just Washington, D.C., but if you look a little broader than that, I think there’s a great hunger in the United States for sensible policies on this.

Right. There were a lot of surveys that came out to that effect after the new EPA rules came out. But so far as the rest of Obama’s presidency and putting pressure on him to take as much action as possible, what do you want to see happen or what do you hope he’ll be able to achieve?

I think he is right in what he said in that interview with Tom Friedman about how the most important policy measure would be to put a price on carbon. That would have enormous implications and ripple effects through not just the U.S. economy, but the world economy. I’d like to see that happen. The other thing that I think is really important to watch is the possibility of a climate deal with China, and that could be really, really important, because you’ve basically got the two climate change superpowers finally coming together on this, and if they created some kind of an agreement to limit emissions, even that could have the de facto effect of creating a global carbon price. And if that happens, wow, we could see change occurring very very rapidly because, frankly, if China and the U.S. were to do that, the rest of the world economies would kind of have to follow suit.

But I would emphasize yet again that those are the policy outcomes; the only thing that’s going to make those things happen is absolute continued and increased popular pressure. The only reason the Keystone pipeline is not already built is because people got into the streets and made it an issue. And you can say that Obama would not have said what he said, not just in the Showtime interview but in his Georgetown speech, and all the things that he’s been doing, none of that would have happened if there had not been people in the streets. So if there’s one take-away message from all this I think it’s the absolute importance of public pressure and indeed, the history of the environmental movement and specifically of the Clean Air Act illustrates that quite strongly. The reason that we got the Clean Air Act, and the Environmental Protection Agency, for that matter, created in the first place was because 20 million people got into the streets on the first Earth Day in 1970 and scared the pants off of a politician named Richard Nixon.

So we can celebrate Obama’s rhetoric but we can’t forget, and we can’t let him forget, that he hasn’t fulfilled his campaign promises.

Absolutely, and he has said to activists, “You need to push me.” And I don’t think that’s just rhetorical. I mean here’s how it works: The president of the United States sits in the Oval Office and he gets the calls from the CEO of Exxon and the CEO of Chevron — believe me, those calls are put through. And the only way any president can have that phone call not become “Oh, well, whatever you say sir,” is to be able to say, “I hear you sir and I’d like to help you, but there are 20 million people out in the street there, and I have to listen to that too.” And that has not been there for most of Obama’s presidency. These are very powerful interests and no president can on his, or someday her own, stand up to Big Oil, any more than they can unilaterally stand up to the insurance industry or Wall Street or the military-industrial complex.