The ratings agency Fitch warned overnight Wednesday it may strip the United States of its AAA sovereign credit rating. Negotiations about the federal budget, the health care reform law, and raising the limit on federal borrowing are back in the Senate after the House's plan collapsed on Tuesday. Despite that view in the markets, many are characterizing what could soon happen as "default." And, instead of default, can we talk about pretty leaves for a second? Tis the season of changing colors in a lot of states. But some recent studies have raised an important question: Will climate change spoil the season?