Scientists behind a "Doomsday Clock" that measures the likelihood of a global cataclysm announced Tuesday civilization remains at "three minutes to midnight."
The Bulletin of the Atomic Scientists unveiled the minute hand on the metaphorical clock in Washington, D.C. The clock reflects how vulnerable the world is to catastrophe from nuclear weapons, climate change and new technologies, according to the bulletin.
California Gov. Jerry Brown joined former U.S. Secretary of State George Shultz and former U.S. Secretary of Defense William Perry for a discussion at Stanford University after the unveiling.
Lawrence Krauss, chair of the bulletin's Board of Sponsors, said the Iran nuclear agreement and Paris climate accord were good news. But he said tensions between Russia and the U.S. have grown, and it is not clear the Paris accord will lead to concrete action to reduce greenhouse gas emissions.
The scientists behind the bulletin adjusted the clock from five minutes to midnight to three minutes to midnight last year, citing climate change, modernization of nuclear weapons and outsized nuclear weapons arsenals as "extraordinary and undeniable threats to the continued existence of humanity."
The minute hand is assessed each year. It has also previously stayed the same and been adjusted in the opposite direction. Most recently in 2010, bulletin scientists cited nuclear talks between the U.S. and Russia and agreement to limit a rise in global temperature for a change from five minutes to midnight to six minutes to midnight.
The Bulletin of the Atomic Scientists was founded in 1945 by University of Chicago scientists who helped develop the first atomic weapons. The clock was created two years later, with midnight symbolizing apocalypse.
The decision to move or leave the clock alone is made by the bulletin's science and security board, which includes physicists and environmental scientists from around the world, in consultation with the bulletin's Board of Sponsors, which includes 17 Nobel laureates.
The closest the clock has come to midnight was two minutes away in 1953, when the Soviet Union tested a hydrogen bomb that followed a U.S. hydrogen bomb test.