The scientists at The Bulletin of the Atomic Scientists have advanced the Doomsday Clock, a symbolic indicator of the nuclear threat to humanity, forward 30 seconds as geopolitical tensions continue to grip the globe.

At 2 minutes to midnight, this is 30 seconds closer than the clock was at this time last year, and the closest the clock has been to the symbolic “midnight” since 1953—the height of the cold war. At that time the Soviet Union had just tested its first hydrogen bomb, and the United States had begun to explore the development of thermonuclear weapons. It would not change again until 1960.

While a grim indicator of where tensions lie around the globe, the Doomsday Clock is still a subjective lens with which to view the state of the world. In reporting by the Washington Post, Rachel Bronson, the current president of the Bulletin which shares 15 Nobel Laureates among its board, the decision to move the clock forward has been spurred by “the failure of President Trump and other world leaders to deal with looming threats of nuclear war and climate change.”

Historically, it has not only been the threat of nuclear weapons or conflict that has driven the Bulletin to move the clock forward or backward. As noted in Bronson’s statement, other factors including climate change, diplomacy, energy crises, and other things may cause adjustments to the Doomsday Clock. In 1991, after the collapse of the Soviet Union, the clock was moved back to 17 minutes to midnight—the highest recorded point since the Doomsday Clock’s creation in 1947.