WATERLOO, Iowa (AP) — Republican presidential hopeful Jeb Bush says he's not sure he would have attended the Paris climate summit because its proposals would hurt the U.S. economy.

The former Florida governor said Tuesday in early-voting Iowa that he's "uncertain" he would have attended the summit if he were president. He says world leaders participating in the summit are exploring policies that are detrimental to the economy.

Key world leaders, including President Barack Obama, have said one of the smartest ways to fight global warming is by taxing or otherwise putting a price on carbon dioxide pollution.

Bush says Americans are hurting economically and carbon pricing could make matters worse. He has said the federal government should invest in research and development to find new energy sources.