As the world grapples with the consequences of global warming, scientists are thinking up new ways to lower the earth’s temperature and to do so quickly. Climate scientist Ken Caldeira discusses some unusual intervention strategies.

In January 2015, the iconic Doomsday Clock moved two minutes closer to midnight. What does that mean? According to the esteemed Bulletin of Atomic Scientists, the world is that much closer to catastrophe. Should we be worried? To explain, is the man who virtually moved the hand himself, climate scientist Richard Somerville.