Over the past decade, billionaire presidential candidate Tom Steyer has reinvented himself from fossil fuel funder to climate crusader. He reached a net worth of $1.6 billion as a hedge fund manager who invested in coal, oil, and gas (among other things). But lately, he’s become better known as an activist and donor hell-bent on removing Donald Trump from office and funding a transition away from the fossil fuels that helped him get rich.

In July, Steyer stepped down from leading his Need to Impeach campaign in order to enter the Democratic primary race. He’s polling at just 1 percent, but he’ll take the stage during the debates tonight. Taking on climate change, he says, is his top priority.

The Verge talked with Steyer about his fossil-fueled past and what he sees for the future of energy.

This interview has been edited for length and clarity.

What is your response now that the president has been impeached?

It is an example to me of grassroots organizing and grassroots power from the people, dragging Washington to do the right thing.

You made money from fossil fuels, and you haven’t fully wound down those investments. Does that conflict with your calls to action on climate change?

Look, when I was running our investment firm, we invested in every part of the economy. Over a decade ago, I realized that the energy that was fueling the economy in America and around the world had this huge unintended consequence of climate change. So I did divest. I did take the Giving Pledge to give the bulk of my money away while I’m alive. I started to organize to work against the climate crisis and to work to resolve it. If there’s any part of it for some legal reason that I haven’t been able to divest in my portfolio, I promised that I would give any money that comes out of it away to charity. So there is no conflict.

“We all come from a fossil fuel economy.”

Really, what I’m asking Americans to do is exactly what I did. We all come from a fossil fuel economy — every one of us — and we need to realize that that’s not something that we intended to have a bad consequence, but it turns out that it does. So we all need to change and do what I did, which is to push as hard as possible toward clean energy and toward addressing the climate crisis.

The US has become a net exporter of natural gas. Would you get the US off of natural gas?

Absolutely. There was a theory 10 years ago that it was the bridge fuel because we could get onto natural gas, and it had half as many greenhouse gases per kilowatt-hour as coal. Turns out, that’s not really true. That theory was, in practice, wrong because of escaped methane. We have the technology to move to clean energy right now. We have the technology to move to wind, solar, and batteries. And that’s what we should be doing. There’s no reason whatsoever to think that natural gas is an effective bridge fuel.

“There’s no reason whatsoever to think that natural gas is an effective bridge fuel.”

What role would nuclear energy play in your climate plans?

Nuclear energy proposals do not compete in terms of cost. Right now, any nuclear proposal is much too expensive based on cost per kilowatt-hour. In addition, there are questions with nuclear about danger, you know, disasters like Fukushima. It’s a real question. There’s also no real plan to dispose of the toxic nuclear waste that lasts for 100,000 years. If we can get nuclear that is cheap where we don’t have the danger of explicit nuclear disasters, and we don’t have a waste disposal problem, then nuclear comes into the picture. But right now, the cheapest fuels that we have are wind and solar. They’re already there; they don’t have the attendant risks that nuclear does. So it doesn’t seem to me to make any sense to go to a more expensive, more dangerous fuel when others are available.

And how about carbon capture technologies?

It’s one of those things where if you could show me that it was actually feasible on a large scale around the world, then carbon capture becomes serious. Right now, it looks much, much, much more expensive than alternatives. And you can’t show me in a practical sense exactly where we’re going to put the CO2. So right now, I put it in the same category as nuclear, which is a promising technology. People are working really hard on it, but we aren’t at the level where you can say it’s ever going to work. If it does, then fantastic.

Your climate plan calls for net-zero carbon emissions by 2045. Will the US still be extracting and burning fossil fuels in a future that’s carbon neutral by 2045?

“This is not business as usual.”

No. Let me be clear: this is my number one priority. I would declare a state of emergency [on climate change] on day one. This is not business as usual. I will use the emergency powers of the presidency to get going on this. You start with environmental justice in the communities where you can’t breathe the air safely or drink the water safely. Leadership in those communities is absolutely critical to getting the right policy, to executing it, and to making sure that you have a justice-based plan. That’s number one. Number two, doing this is going to create millions of jobs across the United States of America, good-paying union jobs. It means rebuilding the country on an accelerated basis. While it’s a crisis that we have to deal with on day one, it is also the biggest opportunity we have ever had to rebuild and reinvent the meaning of America, to take on the biggest challenge in history and succeed.