WASHINGTON D.C.: President Barack Obama will on Wednesday warn that a one-foot rise in sea levels could cost the United States as much as $200 billion, in a speech warning of the security risks of climate change. In a commencement address to the United States Coast Guard Academy, Obama will warn that climate change presents the most serious risk to national security, a risk that is immediate and acute. “You are part of the first generation of officers to begin your service in a world where the effects of climate change are so clearly upon us,” he is expected to say. “Make no mistake, it will impact how our military defends our country. And so we need to act-and we need to act now.” The White House believes that rising sea levels is chief among these risks.