Hill: President Obama laid out a billion-dollar climate change challenge on Saturday, urging the nation to help combat the effects of natural disasters. Can you imagine a more worthy goal, a more worthy legacy, than protecting the world we leave to our children, the president said as he delivered the commencement address at the University of California, Irvine. "U.S. action is critical on climate change, as the world is watching and will follow the U.S.s lead, he said. This is a fight America must...