Let’s talk first about those costs.

A cap-and-trade system would raise the price of anything that, directly or indirectly, leads to the burning of fossil fuels. Electricity, in particular, would become more expensive, since so much generation takes place in coal-fired plants.

Electric utilities could reduce their need to purchase permits by limiting their emissions of carbon dioxide  and the whole point of cap-and-trade is, of course, to give them an incentive to do just that. But the steps they would take to limit emissions, such as shifting to other energy sources or capturing and sequestering much of the carbon dioxide they emit, would without question raise their costs.

If emission permits were auctioned off  as they should be  the revenue thus raised could be used to give consumers rebates or reduce other taxes, partially offsetting the higher prices. But the offset wouldn’t be complete. Consumers would end up poorer than they would have been without a climate-change policy.

But how much poorer? Not much, say careful researchers, like those at the Environmental Protection Agency or the Emissions Prediction and Policy Analysis Group at the Massachusetts Institute of Technology. Even with stringent limits, says the M.I.T. group, Americans would consume only 2 percent less in 2050 than they would have in the absence of emission limits. That would still leave room for a large rise in the standard of living, shaving only one-twentieth of a percentage point off the average annual growth rate.

Image Paul Krugman Credit... Fred R. Conrad/The New York Times

To be sure, there are many who insist that the costs would be much higher. Strange to say, however, such assertions nearly always come from people who claim to believe that free-market economies are wonderfully flexible and innovative, that they can easily transcend any constraints imposed by the world’s limited resources of crude oil, arable land or fresh water.