McKibben's 1989 book "The End of Nature" is described as the first book on climate change for a popular audience. He's also been an active crusader on the topic for decades, co-founding the climate action group 350.org in 2007.

Sonya Diehn talked to him in the media space at the COP21 climate summit in Paris.

DW: What needs to happen for the world to decarbonize?

Bill McKibben: I wrote a piece three years ago called "Global Warming's Terrifying New Math," and it was based on a tiny little report that had come from a couple of financial analysts in the UK who had done the work of adding up all the fossil fuel reserves in the world. It turned out even three years ago we already had five times more fossil fuels in our reserves than we could safely burn.

Once one saw those numbers, one understood that the end to this climate story had already been written. Unless we change the script dramatically, there's no mystery as to what's gonna happen: we're gonna burn up.

Decarbonization means keeping most of the coal and oil and gas that we know about underground and not finding anymore. Stop looking for that, stop digging it up, treat it as we treat the Amazon rainforest: make sure that it stays where it is, intact.

You point out that the best movements always have clear enemies - and you talked about the powerful fossil fuel companies being these clear enemies. Do you still believe that?

We didn't know the half of it in 2012! In the last 10 weeks, thanks to great reporters in America, we've learned that the biggest fossil fuel company, Exxon, knew everything that there is to know about climate change 30 years ago. And instead of telling the truth, they built this elaborate and expensive edifice of denial and disinformation.

The only reason we're here at COP21 is because they lied. If they had told the truth, we could have stopped at COP2 and gotten to work.

The way that power is distributed on our planet is not working well. Global warming is the proof of that, and it could work very differently. If we were to move the world quickly onto sun and to wind, the balances of power on our planet would start to shift, because no one has a monopoly on those things.

All of the best movements have, in addition to having a clear conflict and a clear enemy, also clear leaders. Is that also true of the nascent climate justice movement?

We have no Dr. Martin Luther King for this movement. Maybe it'd be great if we did, but I don't think we're going to get one.

So instead, we have this kind of leaderless movement. The way that I think of it is a fossil fuel resistance, like the French Resistance during the war: spread out, kind of sprawling, and local. That's good, because the fossil fuel industry is spread out, sprawling in every place, and you need to be able to stand up to it everywhere.

But because of the Internet, we're also networked together enough that when we need to, we can come together for the big fights. We were able to come together to beat the Keystone Pipeline in the United States or the big coalmines in Australia. We were able to come together for that and to the Ende Gelände coal action in Germany earlier this year, which was great. And there'll be more like that in the year ahead.

What do people need to be doing to get this decarbonization moving?

The most important thing an individual can do is not be an individual quite so much - come together and join these large movements that perhaps are capable of changing the systems and structures that are causing the problem.

Does that involve pressuring politicians?

Sure, that's part of it. I think sometimes, we probably need to spend more time directly pressuring the companies that tend to own the politicians.

If we really want action, it's better to stop worrying about the cashier at the front of the store and go back and look in the back-room and see where the owner lives, you know?

You've pointed out how the fossil fuel industry has such a massive hold over the political system. What is the best way to loosen that grip?

The only way to loosen that grip is finding a different currency to work in. They have all the money. We will never outspend them. We have the currency of movements: passion, spirit, creativity. Sometimes we have to spend our bodies and go to jail.

The science has been clear for twenty years. We've won the argument, now we have to figure out how to win the fight.

You've also promoted divestments as one of the main kind of factors to push this forward. Do you still believe in that power?

Very much. The divestment movement has turned out to be extraordinarily successful, far beyond our wildest dreams. As of this conference, we announced that portfolios and endowments worth $3.4 trillion divested from fossil fuels.

That's changing the way that markets think about the future.

You've shaped debate and you've been recognized for your lifetime commitment and work. Would you have done anything differently, looking back?

I would have started organizing much sooner.

It took me too long to figure out - I thought we were in an argument, but we were in a fight. And so I kept writing more books and giving more talks, thinking that we would eventually win the argument and everyone would say "Oh yes, you're right, we must do something."

It turned out that I was stupid. It wasn't about data. It was just about power and money, which is what fights are generally about. So once we started organizing, we started doing better.

Getting back to the issue of the enemy: painting fossil fuel companies as villains is negative storytelling …

I don't know if it is negative or positive, it just happens to be the truth. If Exxon had simply told the truth right when they learned it, they could have ended 25 years of faux, phony debate.

They may have broken the planet by themselves. And if I take it personally, maybe it is because as a result, I had to spend my entire adult life engaged in a project that shouldn't have been necessary.

We're here sitting at COP21 - what's your take on the negotiations?

This is the scoreboard, not the game. It reflects what we've done over the last four or five years, how much pressure there's been and it reflects that the price of a solar panel has fallen 80 percent since Copenhagen. That's what's driving what happens here. It's now enough that we can begin to match the fossil fuel industry, but they're still strong enough to keep us from reaching a real agreement that gets us where we need to go.

So the scoreboard is a little better than what it was after Copenhagen. On the other hand it's also later in the game.

Bill McKibben is an American environmentalist, author, and journalist who has written extensively on the impact of global warming. He is co-founder and leader of the anti-carbon campaign group 350.org. In 2014, he won the Alternative Nobel Prize.