In the first town hall of his freshly announced presidential campaign, Mitt Romney yesterday reaffirmed his view that global warming is occurring and that humans are contributing to it, a position that has been rejected in recent years by many Republicans as the issue has taken on a greater partisan tinge. "I don't speak for the scientific community, of course," Romney said. "But I believe the world's getting warmer. I can't prove that, but I believe based on what I read that the world is getting warmer. And number two, I believe that humans contribute to that . . ....