The exact number of nuclear weapons situated across the world is shrouded in mystery, but whatever the number, North Korea's underground test this week is a grim reminder of the devastation and destruction these weapons could unleash.

The Federation of American Scientists estimates that at the end of 2012, there were 17,300 nuclear weapons globally. It said about 4,300 warheads are operational, of which about 1,800 US and Russian warheads are on high alert.

Protest at AWE on CND's 50th Anniversary

Another estimate, from the Stockholm International Peace Research Institute, puts the number of nuclear warheads at 19,000, down form 20,530 at the start of 2011. Other estimates go as high as 36,000.

These weapons are possessed by nine states, United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and North Korea – four more than legally recognised by the 1968 Non-Proliferation Treaty (NPT).

But irrespective of whether they are legally possessed or not, Greenpeace is opposed to the development, testing and use of nuclear weapons. The proliferation of these weapons of mass destruction poses a grave risk to world peace and the future of human kind.

Heightened tension

So we were greatly concerned by news that North Korea conducted its third nuclear test this week, following previous tests in 2006 and 2009. It has heightened tension both regionally and within the UN Security Council.

North Korea said its test had "greater explosive force" than its previous tests, indicating it used a technology that could theoretically be paired with a long-range missile to threaten even the faraway US.

This latest crisis has highlighted the weakness of the non-proliferation treaty and underscores the dangerous connection between nuclear research, nuclear power and nuclear weapons.

Greenpeace's founding voyage more than 40 years ago was aimed at stopping a US nuclear weapons test on Amchitka island off Alaska.

Since then we have achieved some tremendous victories in the campaign against nuclear testing. The US conducted its last nuclear test in 1992 and signed in 1996 the Comprehensive Nuclear Test Ban Treaty.

We have also experienced tragedy.

In 1985, our photographer Fernando Pereira was killed when the Rainbow Warrior was bombed and sunk in Auckland Harbour by the French government trying to shut Greenpeace down for opposing its nuclear weapons testing programme in the Pacific.

And nearly 70 years after we first witnessed the devastating impact of nuclear weapons, we can wait no longer for our leaders to rid the world of this monstrous human invention.

Test site trek

Pledged arsenal reduction

In his State of the Union address on Tuesday, President Barack Obama committed to reducing the US’s nuclear arsenal, pledging to "engage Russia to seek further reductions … and continue leading the global effort to secure nuclear materials that could fall into the wrong hands."

It has been estimated that Obama is committing to reduce the number of nuclear weapons deployed by the US (currently 1,700) by roughly a third – in line with the new strategic treaty with Russia passed in 2009.

However the total size of the US nuclear weapons stockpile is still much larger and is estimated at over 5,000 nuclear warheads, including tactical, strategic, and non-deployed weapons.

According to conservative estimates conducted prior to this announcement, the US is set to spend over the next decade more than US$640 billion on nuclear weapons and related programmes. Obama's proposed cuts could save a staggering $120 billion in the next two decades. 

These are mind-blowing amounts, spent on an instrument that has so far created only pain and suffering for millions, causing death, illness and environmental destruction whenever it was used, tested or produced.

Of the stockpiled weapons, thousands of them remain on high alert, ready to launch at a moment's notice and there have been more than 2,000 nuclear tests conducted to date.

What is clear, however, is that nuclear weapons cannot deliver true security – even for those countries that possess them. By focusing on a fake notion of security, centered on preparing and waging wars, governments are failing to protect their citizens.

It is time we invested our energies in peace, not war.

Compiled by Jen Maman, Greenpeace International peace adviser, and Aaron Gray-Block, Greenpeace International media relations specialist