“Recent calls for the resumption of nuclear testing demonstrate that the terrible lessons of the past are being forgotten - or ignored,” he said.

The International Day was established in 2009 by the UN General Assembly to recall the date of the official closing of the Semipalatinsk nuclear weapons testing site in today’s Kazakhstan on 29 August 1991.

That one site alone saw 456 nuclear test explosions between 1949 and 1989.

Era of nuclear proliferation

In the shadow of the Cold War, the world witnessed an unprecedented era of nuclear proliferation and testing.

Between the years 1954 and 1984 there was on average at least one nuclear weapons test somewhere in the world every week, most with a blast far exceeding the power of the bomb dropped on Hiroshima.

Moreover, nuclear weapons stockpiles have grown exponentially, with the majority far more powerful than the bombs used in Hiroshima and Nagasaki.

This proliferation has left a ‘legacy of destruction’, according to Mr. Guterres, significantly disrupting people’s lives and livelihoods and affecting the environment with traces of radioactivity in even the deepest of ocean trenches.

‘World must speak with one voice’

The UN chief is urging the world to speak with one voice, “to end this practice once and for all”.

He has praised the Comprehensive Nuclear-Test-Ban Treaty as an “essential, verifiable security tool” due to its complete prohibition on all nuclear testing.

He is calling on all countries whose ratifications are needed for the Treaty to enter into force to do so immediately and without conditions.

“Let’s pass the test for humanity – and ban nuclear testing for good,” he concluded.

Read the op-ed here marking the day on our UN News site penned by the President of the General Assembly and head of the Comprehensive Nuclear-Test-Ban Treaty Organization.