I talked to Weaver about his experiences moving from academia into Parliament. An edited transcript of our conversation follows.

Ed Yong: Why did you decide to leave climate science for politics in 2013?

Andrew Weaver: In 1979, when I graduated from high school, the National Academy of Sciences put together a scientific assessment of what will happen if you double carbon dioxide levels. It pointed out that the best estimate was 3 degrees of warming, with a range of 1.5 to 4.5 degrees. In 1988, I was a postdoc in Australia and the IPCC was set up. Its first report said that the best estimate was in the range of 1.5 to 4.5 degrees. I took part in the 2nd, 3rd, and 4th versions. The 4th was published in 2007; there had been tens of thousands of papers, and the best estimate was a warming of 2.5 and 4.5 degrees.

By 2013, there had been 34 years of assessment, and the single most important metric of our collective understanding of how the world will warm hadn’t changed. At some point, one has to question whether we need more science to deal with this problem or whether we need political will.

But many politicians see politics as a career path, so getting re-elected becomes a top priority, and you make promises about what happens in the short term. Decision-makers today won’t see the consequences of their decision in their political lifetime, but those decisions have a profound effect on the environment that future generations have to live with. So the entire issue of global warming is one of intergenerational social equity. Do we care about what we leave behind, about future geopolitical stability, about other species?

I’ve lectured on this a lot and people would say: Politicians are all corrupt. I would argue: That’s what we got. You don’t like them, run yourself. Find someone you can get behind. But there’s only so many times you can do that.

When I was finishing the draft of the 3rd IPCC report, I was asked by the leader of the BC Green Party to run. I said no. Then, I said no again. And again. I think I said yes on the fourth time.

Yong: Why?

Weaver: From 2007 to 2009, I had been involved in British Columbia’s Climate Action Team. Gordon Campbell, the leader of the British Columbia Liberal Party, recognized that climate change was an issue that needed to be dealt with, and an enormous economic opportunity. He put in a suite of policy measures like an innovative carbon tax.

But in 2009, the British Columbia New Democratic Party planned to remove the tax as part of a cynical “axe the tax” campaign. And in 2010, Campbell was replaced by Christie Clark who campaigned to bring liquefied natural gas back to British Columbia, threatening to dismantle a lot of Campbell’s climate leadership. We had a two-party system and no one was doing anything. That’s why I ran with the Green Party.