Greenwire: A group of U.S. climate scientists is urging Congress to quickly pass a strengthened version of the House global warming bill, saying the legislation would provide a basis for stronger federal policies. The letter [pdf] signed by 20 scientists says strong U.S. leadership is needed to avert a “rapidly developing global climatic catastrophe.” The House climate and energy bill proposed by Democratic Reps. Henry Waxman of California and Ed Markey of Massachusetts offers a “powerful …