Could global warming trigger a sudden catastrophe

Recently, researchers -- and even the U.S. Defense Department -- have investigated the possibility of abrupt climate change, in which gradual global warming triggers a sudden shift in the earth's climate, causing parts of the world to dramatically heat up or cool down in the span of a few years.

In February 2004, consultants to the Pentagon released a report laying out the possible impacts of abrupt climate change on national security. In a worst-case scenario, the study concluded, global warming could make large areas of the world uninhabitable and cause massive food and water shortages, sparking widespread migrations and war.

While this prospect remains highly speculative, many of global warming's effects are already being observed -- and felt. And the idea that such extreme change is possible underscores the urgent need to start cutting global warming pollution.