Most economists in the field think the rational thing to do is to put a price on emissions of greenhouse gases, which would in turn raise the price of gasoline and of electricity generated from coal. That would discourage emissions in the short run — people might, say, buy more efficient cars or better insulate their houses to avoid higher bills — and it would tilt the market in favor of cleaner energy sources in the long run. It would also have some valuable side benefits, like cleaning up the localized pollution from coal-burning power plants that is chopping years off people’s lives in Chinese cities.

But what should the price of greenhouse emissions be? This is where things get sticky.

If you wanted only to reduce the damages that are virtually certain to occur, you might come up with a pretty low number — say, a few extra cents tacked on at the gas pump. But that course would rest on the assumption that climate change will proceed fairly smoothly. In other words, what we will see might look a lot like the changes we have already seen, except gradually becoming more intense. Human society might adjust to that pretty well through normal market behavior.

But as the United Nations panel pointed out, the physical scientists see a distinct risk that things will not work that way. We might cross some temperature threshold beyond which a rapid, highly disruptive change in the climate would occur.

We know this can happen because it has happened in the earth’s geologic history, before seven billion people were in harm’s way. For instance, as the last ice age was ending, glaciers melted so fast at one point that the sea level rose at the rate of perhaps a foot per decade, 10 times faster than today.

Suppose we were to spew enough heat-trapping gas into the air to produce a rapid collapse of the polar ice sheets and thus a rapid rise of sea level. Human society could be thrown into panic. Tens of millions of people might have to be moved. Trillions of dollars of productive capital, including many of the world’s major coastal cities, might have to be abandoned.

Because the likelihood of this sort of thing is unknown, economists cannot really figure out how to work such risks into their economic models. But they certainly understand them in principle. That is why many of them recommend that we push harder on climate policies than we otherwise might — in other words, set a higher emissions price — to buy ourselves some insurance against the worst-case possibilities.

Whether you agree with that is not, in the end, an economic question.

It is a question of how much you believe you owe those living in the future — not just your own children or grandchildren, but the generations of people who will come long after we are gone.