According to urban legend, the international climate scientists have told us we must reduce carbon emissions by 80 percent by 2050. The U.N. climate science group, the IPCC, has said nothing of the kind. But they have said something about what it would take to hold greenhouse gas concentrations down to 450, 550, or 650 parts per million. They just don’t say which target we must shoot for.

The environmentalists rule that we must target “80 by 2050,” just reflects their selection of the 450 target, and some studies summarized by the IPCC. These say that the developing countries—that’s us—must push greenhouse gas concentrations down to 80 percent below 1990 levels by 2050 to make up for what the rest of the world is likely to be doing.