Doomsday Clock clicks half a minute toward midnight

Arizona State University New Origins Initiative Director Lawrence Krauss (C) and Bulletin of the Atomic Scientists Science and Security Board member Thomas Pickering (R) unveil the latest version of the Doomsday Clock with Stockholm Environment Institute Senior Scientist Sivan Kartha (L) and Center for Strategic and International Studies' Proliferation Prevention Program Director Sharon Squassoni during a news conference at the National Press Club January 26, 2016 in Washington, DC. The bulletin's Science and Security Board takes into consideration 'the number and kinds of nuclear weapons in the world, the parts per million of carbon dioxide in the atmosphere, the degree of acidity in our oceans and the rate of sea level rise' when setting the clock as a warning against self-destruction.