More than three dozen national security officials, members of Congress and military leaders are warning of the threat climate change poses to U.S. national security, the latest in an indicator that U.S. intelligence and national security circles are increasingly worried about a warming planet. In a new bipartisan open letter, they stress the need for urgent action and call on both public and private support to address issues that included forced migration and the displacement of vulnerable communities, as well as the dangers related to food production during extreme weather events.