But the area he’s just as worried about, said Obama, “is how climate change could end up having profound national security implications in poorer countries. We’re obviously concerned about drought in California or hurricanes and floods along our coastlines and the possibility of more powerful storms or more severe droughts. All of those things are bread-and-butter issues that touch on American families. But when you start seeing how these shifts can displace people — entire countries can be finding themselves unable to feed themselves and the potential incidence of conflict that arises out of that — that gets your attention. There’s a reason why the quadrennial defense review — [which] the secretary of defense and the Joints Chiefs of Staff work on — identified climate change as one of our most significant national security problems. It’s not just the actual disasters that might arise, it is the accumulating stresses that are placed on a lot of different countries and the possibility of war, conflict, refugees, displacement that arise from a changing climate.”

Syria couldn’t manage a four-year drought when it had a government, and that drought helped fuel the uprising there, because the government did nothing for the people. Imagine what will happen if they have another prolonged drought and they’ve destroyed half their country?

“Which gives you a sense of what happens in a lot of these countries that are just barely hanging on,” said Obama. “They don’t have a lot of margin for error, and that has national security implications. When people are hungry, when people are displaced, when there are a lot of young people, particularly young men, who are drifting without prospects for the future, the fertility of the soil for terrorism ends up being significant. And it can have an impact on us.”

What is the one thing you would still like to see us do to address climate change? Said Obama: put a price on carbon.

The way we’ve solved previous problems, like acid rain, he noted, “was that we said: ‘We’re going to charge you if you’re releasing this stuff into the atmosphere, but we’re going to let you figure out — with the marketplace and with the technology’ ” how best to mitigate it. But “you can’t keep dumping it out in the atmosphere and making everybody else pay for it. So if there’s one thing I would like to see, it’d be for us to be able to price the cost of carbon emissions. ... We’ve obviously seen resistance from the Republican side of the aisle on that. And out of fairness, there’s some Democrats who’ve been concerned about it as well, because regionally they’re very reliant on heavy industry and old-power plants. ... I still believe, though, that the more we can show the price of inaction — that billions and potentially trillions of dollars are going to be lost because we do not do something about it — ultimately leads us to be able to say, ‘Let’s go ahead and help the marketplace discourage this kind of activity.’ ”