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.

This was the year climate change vanished from the political agenda—and then suddenly reappeared, after Hurricane Sandy shook the country. It was just a few years ago that President Obama flew to Copenhagen to rescue faltering climate-treaty talks amid bipartisan calls for global warming action. But in 2012, there wasn't a single congressional proposal or hearing on climate legislation. Neither was there mention of climate change on the presidential campaign trail, or in the debates for the first time in decades. 

Aside from Mitt Romney's recent jab at Barack Obama's concern over global warming—and the president's tit-for-tat response—climate change has been largely under the radar in the campaign. But several groups, backed by hundreds of thousands of petitions, are trying to change that, at least for one night. Nine environmental organizations Friday delivered more than 160,000 petitions to Jim Lehrer urging him to ask a question about climate change during Wednesday's first presidential debate. 

The words global warming used to mean something. When the term became popular in the early 1990s, it sounded like something out of a science-fiction movie. Today, however, it is thrown around casually and most people seem to have forgotten its implications. (Similarly lost is the significance of April 22 — Earth Day; don’t pretend like you remember.) Of course, there are those dutiful citizens who are doing their best to combat global warming: refusing plastic bags at the bodega; driving under 60 mph with the windows up and the air-conditioner off; and buying recycled paper towels. But the actions of a few have next to no impact on global climate change.