Former California Gov. Jerry Brown is executive chairman of the Bulletin of the Atomic Scientists. Former US Defense Secretary William Perry is chairman of the Bulletin of the Atomic Scientists Board of Sponsors. This piece is an adaptation of the Bulletin's Doomsday Clock statement. The views expressed in this commentary are those of the authors. View more opinion on CNN.

(CNN) On Thursday, the Bulletin of the Atomic Scientists set the Doomsday Clock at two minutes to midnight. Welcome to what we call "the new abnormal." This phrase describes the catastrophically dangerous world in which we live.

Jerry Brown

William Perry

We have to go back 66 years, to 1953, to find a time of equal danger: The Soviet Union had just tested a hydrogen bomb. Eastern Europe was in the iron grip of the Soviet Union. There was danger of a military conflict erupting in Berlin. And US troops in West Germany, fully expecting an invasion, were preparing to use tactical nuclear weapons against the invaders.

In 2018, Bulletin of the Atomic Scientists experts equated the nuclear danger to that dangerous time in the Cold War, setting the clock to two minutes to midnight. We have kept it there this year.

Why? Because a new Cold War is underway -- one equivalent to the most dangerous year of the first Cold War. Once more, we're putting at risk the survival of civilization. During the Cold War, the United States and the Soviet Union were, in effect, playing Russian roulette. We won that gamble, more by good luck than by good management. During the Cuban Missile Crisis, there were two close calls that might have initiated a full-scale nuclear exchange. Subsequently, there have been false warnings of incoming missiles both to Russia and to the United States.

So, why are we making that gamble again?

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