A perfect self-driving car doesn’t exist yet, nor has the world solved global warming. But it’s surprising that, by the standards that we’d expect in a car to keep its occupants safe, the governments of the world haven’t stepped on the brakes to avoid planetary-scale global warming disaster—a 100-year-storm hitting New York every other year, frequent and massive droughts, inundated coastal cities. In 1995, the Intergovernmental Panel on Climate Change declared that it was “more likely than not” the case that global warming was caused by human activity. By 2001, it had progressed to “likely.” By 2007, it was “very likely.” By 2013, it was “extremely likely.” There’s only one step left in official IPCC lingo: “virtually certain.”

But we can’t possibly want to wait for that. The 1995 declaration of “more likely than not” should have been plenty to convince us that keeping up the status quo—for two more full decades, by now—was the wrong call. Of course, the world’s systems of governance don’t operate as slickly as an electric engine or an automatic driving algorithm dreamed up by the world’s best engineers. They’re a veritable mess; the technical political-science term used in the context of the climate, "regime complex," doesn’t sound much better.

The problem at hand is similarly messy: There’s no single technology to rescue the world from hitting the global-warming wall. It takes channeling the actions of seven billion individuals who can’t be counted on to do the right thing voluntarily. Changing policy, in turn, takes votes: votes against a system that is pretending to be doing just fine speeding along at 65 miles an hour.

Opinions differ on whether the 1997 Kyoto Protocol that followed on the heels of the “more likely than not” determination has had a significant impact on global emissions. No one would say that it was close to enough. There are hopeful signs in some places, but if anything, the world has since been speeding up on its collision course rather than slowing down.

So how certain does science have to be for the world to act? If “more likely than not” was not enough to act in a way that is commensurate with the magnitude of the challenge, will “extremely likely” turn out to have been sufficient?

The language economists have developed to assess future unknowns can help give solid answers to these questions. Talk of "uncertainty" leaves itself open to uninformed calls to "wait and see." Even though "uncertainty" is technically worse than "risk," the latter is hands-down the more appropriate term, and economists know how to think about risk.

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There are three points to be deduced from the overwhelmingly likely conclusion that humanity is causing climate change. Only one of them is positive.

The first piece of bad news is that we humans are, in fact, increasing global temperatures and sea levels alike. It would have been cause for celebration if, say, the 2013 IPCC report decided that science had gotten it wrong all along. But modern atmospheric science instead once again confirmed the basic ideas of high school chemistry and physics, going back to the 1800s: More carbon dioxide in the atmosphere traps more heat.