AP: Wisconsin U.S. Senate candidate Ron Johnson said Thursday that global warming was an “unproven” science that shouldn’t be used to dictate U.S. policies. The Republican business owner said domestic efforts to reduce global warming would hurt American businesses and send jobs to countries that have fewer restrictions. Johnson said it would be irresponsible to build U.S. policy on the basis of unsubstantiated theories. “The point is, because we’re not certain, because it’s not …