Mayor Bloomberg is saying American “political science” is hampering the effort to combat climate change and causing starvation around the world.

Speaking at the World Science Summit at Columbia University yesterday, Mr. Bloomberg said global food shortages are caused by American corn ethanol subsidies kept in place to secure votes. He described the policy as “special interest politics, plain and simple.”

“For years, research has questioned the environmental benefits of corn ethanol, and now widespread production of corn ethanol has turned out to be an environmental and economic calamity,” he said.

Mr. Bloomberg also criticized proposals to lower or suspend the federal gas tax, noting that even though political candidates support such a move, economists overwhelmingly oppose the policy.

Senators McCain and Clinton have incorporated a suspension of the gas tax into their presidential platforms.

Mr. Bloomberg praised Governor Crist of Florida, who many have discussed as a potential running mate for Mr. McCain, for calling for reduced tariffs on sugar ethanol from Brazil, a move that could benefit the environment but hurt American businesses in the short term.

“It may seem counterintuitive for a governor to appear to undercut one of his state’s biggest industries,” Mr. Bloomberg said. “But real leaders can see the bigger picture beyond the narrow and immediate concerns.”

He touted New York’s efforts to reduce smoking as well as recently enacted laws mandating a 30% reduction in city government’s carbon emissions by 2017 as examples of policies that he said reflected legitimate science.