In May, activist organization Oxfam, which has become less focused on feeding the world and more focused on global warming, published a study showing that food prices in the future would be much higher, to a large extent because of global warming. Oxfam concluded that wheat prices would increase 50 percentage points more by 2030 because of global warming. The media lapped it up, and so, too, did "green" business organizations.

However, neither Oxfam nor the media pointed out that the study was based on a single peer-reviewed paper, and within that paper it focused only on the worst-case scenario. In the paper's best-case scenario, global warming will cause wheat prices to decrease (because of increased production in many of the temperate bread baskets in the world). Even in the central, more likely scenario, the paper finds that global warming would cause wheat prices to drop, not increase. Remarkably, this is true for almost all of the studied food staples, including rice and oilseeds.

In the report, Oxfam advocated constructive policy changes such as the dismantling of support for biofuels and greater investment in adaptation. However, the organization's key focus, as outlined in the summary, lies elsewhere: Success "will depend on political leaders agreeing [to] a fair and ambitious global deal on climate change."

This would be a very ineffective way of responding to Oxfam's concern for the world's poor of rising food prices in 2030. Even if all politicians signed up to the most comprehensive carbon cut deal imaginable, reducing emissions by 80 percent by midcentury (or 50 percent below 1990 levels by 2055), the temperature reduction by 2030 would be an immeasurable one-hundredth of one degree Celsius. Only by the end of the century would temperatures really start to be reduced.

That is, even our most extreme—and unrealistic—carbon-cutting efforts would not make a difference for the world's poor in 2030. Even a complete stop from emissions by midcentury would only reduce temperatures by one-and-a-half hundredth of a degree by 2030, because of the long lags in the climate system.

If we want to help the world's poor avoid the pain of higher food prices, we should focus on developing better and more nutritional crop varieties, getting more fertilizer to farmers, fighting for freer trade, and, of course, the elimination of biofuel support. Those are the policies that would make a real impact on food prices. A carbon deal would do virtually nothing. As I have argued elsewhere, ramping up green energy research should be at the center of any response to global warming.

If we were to follow the activists' core advice and pursue a carbon deal, we would spend trillions of dollars and achieve nothing by 2030. (That's setting aside all of the political barriers that have so far made such a deal impossible). The Baptists would feel righteous, the bootleggers would be richer, and the politicians would look good. But we'd all be worse off.