Gernot Wagner is a climate economist at Columbia Business School. His research, writing, and teaching focus on climate risks and climate policy.

Gernot writes a monthly column for Project Syndicate and has written four books, including Geoengineering: the Gamble and Climate Shock. Before joining Columbia and serving as faculty director of the Climate Knowledge Initiative, Gernot taught at NYU and Harvard.

In this conversation I kept coming back to this hope that climate action could be, in some ways, uncomplicated. If the primary goal is to stop greenhouse gas emissions as soon as possible in order to deal with this as a genuine emergency, it should be simple. But, within the existing system of global capitalism that we have, though, how is that going to happen? Can it happen?

I’ve been trying to think about this by having conversations with people like Gernot, people like Kyla Tienhaara, Seth Klein, Mark Paul and others to try to get to the bottom of it. It’s tough, but these interviews, which I’ll release in the coming weeks, have been helpful. We’re at a point where, according to economists like Robert Pollin, at least 1-2 per cent of global GDP will need to be spent pretty much immediately on investments in renewable infrastructure to radically reduce emissions. Global GDP is about $80 trillion. How does that amount of globally coordinated investment happen under capitalism? It’s a huge shift in the nature of the whole economy.

One of the reasons I wanted to return to Wagner’s writing is that I’ve been helped a lot by his explanation of the social cost of carbon, and especially by the way he writes about considerations of equity and justice in determining the social cost of carbon. It radically increases the social costs, or damages created, by emissions if we factor in issues of equity. The number skyrockets, validating any and all investments in climate mitigation and adaptation. How could that sort of information become more central to decision-making and policy-making?

We definitely get into the weeds here. I’m still processing the discussion we have about “green growth” vs. the “Green New Deal” vs. degrowth. I still can’t say where I land on the question of whether decarbonization needs to happen in a textbook degrowth way. It’s hard to balance expediency and strategy here, and yet, increasingly, the debate about economic transformation to fight climate change hinges on our receptivity to growth or degrowth.

What I like is that there is room here for the debate. We need to rapidly phase-out fossil fuels. That much is certain. In fact, we need to fully ban fossil fuels. How that decision gets made and what form action takes—at what speed and with what consequences—is still an open question.