The Doomsday Clock Explained: How Close Are We to Midnight?

It is not a real countdown or a scientific prediction, but a powerful warning device — a way for leading scientists to communicate, in a single image, how dangerous they judge our moment in history to be. This guide explains what the Doomsday Clock is, who sets it and how, its history of movements, what drives it toward midnight, and whether it actually does any good.

What Is the Doomsday Clock?

The Doomsday Clock is a metaphor, displayed as a clock face, for how close humanity is to destroying the world with its own technologies. The closer the hands are set to midnight, the closer the scientists believe we are to global catastrophe. It was created in 1947 by the Bulletin of the Atomic Scientists, a group founded by researchers who had worked on the atomic bomb and wanted to warn the world about the dangers of nuclear weapons.

Originally focused solely on the nuclear threat, the Clock has evolved to reflect the full range of human-made existential dangers. It is updated once a year, and each setting is accompanied by a detailed statement explaining the reasoning. The Clock is deliberately symbolic — its purpose is to capture attention and convey urgency, not to measure time literally.

Who Sets It and How

The Doomsday Clock is set by the Bulletin’s Science and Security Board, a panel of scientists and security experts, in consultation with the Bulletin’s Board of Sponsors, which has included numerous Nobel laureates. Each year, the board reviews global developments across several categories of risk and debates whether the world has become more or less dangerous over the past year.

Based on that assessment, they decide whether to move the Clock closer to or further from midnight, or leave it unchanged, and they publish a statement laying out the factors behind the decision. The judgement is expert opinion rather than a calculated formula, which is both its strength — it synthesises broad expertise into a clear signal — and a source of criticism, since it is inherently subjective.

A History of the Clock’s Movements

The Clock has moved many times since 1947, tracking the rise and fall of global tensions.

The trend in recent years has been steadily toward midnight, reflecting the board’s growing alarm about overlapping global dangers. The 17-minute mark of 1991 stands as a reminder that the Clock can also move back when the world becomes safer.

What Pushes It Toward Midnight (nukes, climate, AI, bio)

Modern Doomsday Clock decisions weigh several intertwined categories of existential risk. Nuclear weapons remain the original and central concern — arsenals, arms races, and the danger of conflict between nuclear-armed states. Climate change is now a major factor, given its potential to destabilise societies and ecosystems worldwide. Disruptive technologies, especially advances in artificial intelligence, have become a growing concern, as has the threat of engineered or naturally emerging biological dangers. The board also weighs the erosion of the international cooperation and arms-control agreements needed to manage these risks. The 2026 statement specifically cited a failure of global leadership in confronting these compounding threats.

Nuclear War and Nuclear Winter as Drivers

Of all the threats, nuclear war has always loomed largest, because it could cause sudden, civilisation-ending devastation. Beyond the immediate destruction of a nuclear exchange, scientists warn of nuclear winter — a scenario in which soot and smoke from burning cities rise into the atmosphere, block sunlight, and cause a sharp global cooling that could devastate agriculture and cause widespread famine far from any blast.

This is why nuclear arsenals weigh so heavily in the Clock’s setting. The full scientific picture of such an event — from the blasts themselves to the long climatic aftermath — is explored in what if all nuclear weapons detonated at once, and the underlying physics of the weapons is explained in our article on nuclear fission.

Is the Clock Actually Useful?

The Doomsday Clock has its critics. Some argue it is too subjective, too pessimistic, or that compressing diverse and very different risks into a single number oversimplifies them. Others note that it has never literally predicted anything, since it is a symbol rather than a forecast.

Its defenders counter that this misses the point. The Clock is a communication tool, designed to cut through complexity and make abstract, slow-moving dangers feel immediate and real. Each year it generates global headlines and public conversation about threats that might otherwise be ignored. Whether or not one agrees with a particular setting, the Clock has succeeded for over 75 years at keeping existential risk in the public eye — which was always its purpose.

The Bigger Question

The Doomsday Clock distils humanity’s existential risks into a single, sobering image — and nuclear weapons have always been the heaviest hand pushing it toward midnight. But what would actually happen if those weapons were ever used on a global scale, from the immediate devastation to the lasting nuclear winter that could follow? That is the scenario examined in what if all nuclear weapons detonated at once.

The science of the weapons themselves is covered in our article on nuclear fission. Explore more about the threats facing civilisation on the Earth & Humanity Survival hub.

Watch the nuclear scenario to see what is really at stake as the Clock ticks toward midnight.