If the US resumes nuclear weapons testing, this would be extremely dangerous for humanity

US President Donald Trump has instructed the Pentagon to resume nuclear weapons testing immediately, “on an equal basis” with other countries’ testing programs.

If Trump is referring to the resumption of explosive nuclear testing, this would be an extremely unfortunate, regrettable step by the United States.

It would almost inevitably be followed by tit-for-tat reciprocal announcements by other nuclear-armed states, particularly Russia and China, and cement an accelerating arms race that puts us all in great jeopardy.

It would also create profound risks of radioactive fallout globally. Even if such nuclear tests are conducted underground, this poses a risk in terms of the possible release and venting of radioactive materials, as well as the potential leakage into groundwater.

The Comprehensive Nuclear Test Ban Treaty has been signed by 187 states – it’s one of the most widely supported disarmament treaties in the world.

The US signed the treaty decades ago, but has yet to ratify it. Nonetheless, it is actually legally bound not to violate the spirit and purpose of the treaty while it’s a signatory.

What testing is used for, and why it stopped

In earlier years, the purpose of testing was to understand the effects of nuclear weapons – for example, the blast damage at different distances, which provides confidence around destroying a given military target.

Understanding the consequences of nuclear weapons helps militaries plan their use, and to some extent, protect their own military equipment and people from the possible use of nuclear weapons by adversaries.

But since the end of the second world war, states have mostly used testing as part of the development of new weapons designs. There have been a very large number of tests, more than 2,000, mostly seeking to understand how these new weapons work.

The huge environmental and health problems caused by nuclear testing prompted nations to agree a moratorium on atmospheric testing for a couple of years in the early 1960s. In 1963, the Partial Test Ban Treaty banned nuclear tests in all environments except underground.

Since then, nuclear-armed states have stopped explosively testing at different times. The US stopped in 1992, while France stopped in 1996. China and Russia also aren’t known to have conducted any tests since the 1990s. North Korea is the only state to have openly tested a nuclear weapon this century, most recently in 2017.

These stoppages came in the 1990s for a reason: by that time, it became possible to test new nuclear weapon designs reliably through technical and computer developments, without having to actually explode them.

So, essentially, the nuclear states, particularly the more advanced ones, stopped when they no longer needed to explosively test new weapon designs to keep modernising their stocks, as they’re still doing.

Worrying levels of nuclear proliferation

There is some good news on the nuclear weapons front. The Treaty on the Prohibition of Nuclear Weapons has now been signed by half the world’s nations. This is a historic treaty that, for the first time, bans nuclear weapons and provides the only internationally agreed framework for their eventual elimination.

With the exception of this significant development, however, everything else has been going badly.

All nine nuclear-armed states (the US, China, Russia, France, the United Kingdom, India, Pakistan, North Korea and Israel) are investing unprecedented sums in developing more accurate, stealthier, longer-range, faster, more concealable nuclear weapons.

This potentially lowers the threshold for their use. And it certainly gives no indication these powers are serious about fulfilling their legally binding obligations to disarm under the Nuclear Non-Proliferation Treaty.

Moreover, multiple nuclear-armed states have been involved in recent conflicts in which nuclear threats have been made, most notably Russia and Israel.

Worryingly, we have also seen the numbers of nuclear weapons “available for use” actually start to climb again.

This includes those in military stockpiles, those that have been deployed (linked to delivery systems such as missiles), and those on high alert, which are the ones most prone to accidental use because they can be launched within minutes of a decision to do so. All of these categories are on the increase.

Russia, in particular, has weapons we haven’t seen before, such as a nuclear-powered, nuclear-armed cruise missile that President Vladimir Putin said on Sunday his country has successfully tested. China, too, is embarking on a rapid build-up of nuclear weapons.

And the US has just completed assembling a new nuclear gravity bomb.

A new START treaty also not moving forward

Nearly all of the hard-won treaties that constrained nuclear weapons since the end of the Cold War have been abrogated.

There’s now just one remaining treaty constraining 90% of the world’s nuclear weapons, which are in the hands of the US and Russia. This is the New START Treaty, which is set to expire in February next year.

Putin offered to extend that treaty informally for another year, and Trump has said this is a good idea. But its official end is just four months away, and no actual negotiations on a successor treaty have begun.

The US has also said China needs to be involved in the successor treaty, which would make it enormously more complicated. China has not expressed a willingness to be part of the process.

Whether anything will be negotiated to maintain these restraints beyond February is unclear. None of the nuclear-armed states are negotiating any other new treaties, either.

All of this means the Doomsday Clock – one of the most authoritative and best-known assessments of the existential threats facing the world – has moved forward this year further than it has ever done before.

It’s really an extraordinarily dangerous time in history.