On 6 August 1945, the United States dropped an atomic bomb on Hiroshima, and the world changed for ever. As people everywhere commemorate the 75th anniversary of that first nuclear attack, we face a bigger threat to our existence than at any time since.

Two years after Hiroshima, and the second bomb that was dropped on Nagasaki three days later, a group of scientists who had been involved in the bombs’ development created a ‘doomsday clock’ as a warning to humanity. Each year a group of experts sets the ‘clock’ to indicate the risk of catastrophe ‘from nuclear weapons, climate change and disruptive technologies’. This January they moved the clock forward to 100 seconds to midnight – closer even than during the Cold War.

Our current world leaders have ended or undermined hard-won nuclear treaties, incited conflict between nuclear states, and lowered the barriers to nuclear war. They have abandoned even attempts at international co-operation in favour of an unabashed pursuit of their own domestic interests, or – more accurately – the short-term interests of their business elite. And they have used campaigns of disinformation to sow distrust in the organisations and knowledge that are needed to hold back this march towards oblivion.

Today’s commemorations began with a socially-distanced and masked ceremony in Hiroshima itself. As the globe turns, we will hear many fine words spoken and see many candles lit; and we will read memories of the survivors. But by tomorrow this will be yesterday’s news, and it will be politics as usual.

If today’s commemorations are to have any purpose it is important to understand and change those politics, and we can’t wait for the politicians to act. They will only move if pushed from below. During the Cold War, tens of thousands marched and protested against nuclear weapons. Last year, even more marched against climate change. The impact of covid-19 has derailed such protests and provided a cover for an even more aggressive and authoritarian politics, but it has also demonstrated a widespread will for change.

The doomsday clock is not there to make us despair. Its purpose is to jolt the world into action. The Bulletin of Atomic Scientists, who made and run it, is driven by a belief that because humans created these conditions, humans can also control them.