Here’s the bad news: we’ve all got just 100 seconds to live. Here’s the good news: they’re metaphorical seconds, but the fact is we’ve got just 100 of them and when they tick down, it really could be the end of human life.

That grim assessment comes from this morning’s update of the Bulletin of the Atomic Scientists‘ Doomsday Clock, announced at a press event in Washington, DC, during which the venerable nuclear watchdog group made its annual announcement of how close humanity is to destroying itself by the twin threats of nuclear weapons and climate change. The position of the clock’s hands is determined by the Bulletin’s Science and Security Board, along with its Board of Sponsors, which includes 13 Nobel laureates.

This morning’s announcement was attended by multiple luminaries in the fields of science and politics, including former California Governor Jerry Brown, former United Nations Secretary General Ban Ki-moon, and Mary Robinson, former President of Ireland as well as former U.N. High Commissioner for Human Rights.

But it was the members of the Science and Security Board who did most of the talking and gave voice to much of the peril humanity faces. Going into today, the hands stood at two minutes to midnight, the closest they’d ever been in the 75 years the Bulletin has been publishing; the furthest they’ve ever been was 17 minutes to midnight, in 1991, after the fall of the Soviet Union and the end of the Cold War. Now they’ve set a new and ominous record.

“The world has entered the realm of the two-minute warning, when danger is high and vigilance is low” said Rachel Bronson, President and CEO of the Bulletin. “If decision makers fail to act, citizens around the world should rightfully echo the words of [climate activist and TIME Person of the Year] Greta Thunberg: ‘How dare you?'”

Multiple factors went into this year’s announcement, including the U.S.’s withdrawal in August from the Intermediate Range Nuclear Forces treaty with Russia. The decision to move the clock forward was made in November, however, which was actually before some of the most ominous developments in the nuclear theater, with Iran threatening to leave the nuclear-control agreement reached under the Obama Administration and abrogated by President Trump, and North Korea announcing that it no longer felt bound by a self-imposed nuclear moratorium, a development it described acidly as a “Christmas gift” to the U.S.

“Since the United States withdrew from the nuclear agreement, Iran has been steadily stepping up its nuclear activity,” said Sharon Sasquoni, research professor at The George Washington University and a member of the Bulletin’s board. “In North Korea there had been hope that Mr. Trump’s unorthodox approach might bring the country to the negotiating table. But now, [President] Kim [Jong-un] has said his country would demonstrate a new nuclear capability and he would press ahead even without sanctions relief.”

The argument for the climate’s role in moving the doomsday clock’s hands—a factor that was added to the Bulletin’s deliberations only in 2007—was made by Silvan Kartha, another Bulletin board member and a senior scientist at the Stockholm Environmental Institute. In 1953, the only other time the hands had stood at two minutes to midnight, “the idea of human-caused climate change was a subject of mere academic curiosity,” Kartha said. “Since that time, greenhouse gases have increased six-fold and the Earth has warmed by 1 degree Celsius.”

As a reminder to climate deniers who argue that 1º C hardly sounds like much, Kartha not only stressed that the thermometer is climbing higher still, but that it took only a drop of a handful of degrees to plunge the world into the last Ice Age, and just a five degree increase in temperatures to thaw the planet back out. Five degrees added to present global temperatures could be disastrous. “If we push the climate to the opposite of an Ice Age,” Kartha said, “we have no guarantee that the environment will remain hospitable to human life.”

There is admittedly more than a little of melodrama in holding so somber an event to set the non-existent hands on a non-existent clock . But the fact is, the Bulletin has been a respected arbiter of how grave the nuclear threat has been since the clock was first created in 1947 and the hands were set at seven minutes to midnight. The 1953 jump to two minutes was in response to both the U.S. and the Soviet Union testing thermonuclear weapons, in which the explosive power comes not from atomic fission, but hydrogen fusion—the same titanically energetic process that powers the sun.

The hands edged back to seven minutes to midnight over the next few years, as Washington and Moscow avoided direct clashes during such flash-point moments as the 1956 Suez Canal crisis. The 1962 Cuban missile crisis actually pushed things back further still, to 12 minutes, because the near-nuclear war seemed to scare both the U.S. and U.S.S.R. straight, leading them to install a hot line between the Kremlin and Washington and to sign the Partial Test Ban treaty.

The Vietnam war caused the hands to creep closer again, to seven minutes in 1968, before President Nixon’s 1972 brokering of the SALT and ABM treaties—limiting strategic arms and anti-ballistic missiles—pushed them back to 12 minutes. Tensions with the Soviet Union during the Reagan years moving things ahead to just three minutes from doom, before the dramatic post Cold War improvement in 1991, when 17 minutes separated us from the end.

Now, in 2020, we’re closer than we’ve ever been. It’s worth remembering, that if doomsday does arrive, it will not be the result of a global plague we did not see coming and were helpless to stop, or of an asteroid strike like the one that wiped out the dinosaurs. Instead, we will be the authors of our own end, a species, in effect, committing global suicide.

“It is madness,” Kartha said simply during the press conference, regarding policy-makers’ heedlessness to the climate emergency. If so, it’s part of a larger madness from which we have only 100 symbolic seconds to recover.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.