Some climate scientists argue that recent warming trends started in 1850, rose sharply until 1940, then decreased for 35 years. This is not what you would expect if warming was caused mainly by carbon emissions. They also point out that there were significant warming periods in Roman and Medieval times that obviously were not man made.

But even the skeptics are beginning to admit that carbon might be adding to natural warming trends. Given this, and given the fact that carbon pollutes the environment in any case, it does seem sensible to at least take some painless steps to reduce carbon emissions.

The most obvious of these are to drastically increase taxes on gasoline and to increase the use of nuclear power.

Higher gas taxes could be made revenue-neutral by giving the taxes back to the public elsewhere, maybe with tax credits for more fuel efficient cars. If gas were $4 a gallon, hybrid cars would become the norm and their prices would drop. The availability of cheaper hybrid cars, or cars using other low-emission technologies, would benefit the developing world even more than developed countries, since the former are farther behind in cleaning up air pollution.

Nuclear power, despite its reputation, is cleaner and safer than its carbon-based alternatives, even once the problem of waste storage is factored in. So it is worth shifting to nuclear power just to have cleaner air, not to mention curbing global warming.