The after-effects of a nuclear war could include up to two billion people dying of starvation as dramatic changes in weather led to world-wide crop failures.
The fight to get rid of nuclear weapons goes on, but international dynamics make it hard, writes Lyndon Burford.
The world's largest nuclear meeting, the five-yearly Review Conference of the nuclear Non-Proliferation Treaty (NPT), has just closed at the United Nations headquarters in New York.
Representatives of 160 countries, including New Zealand, attended the conference, with observers from dozens of nongovernmental organisations.
After a month of negotiations, the conference failed to reach consensus on effective measures to advance nuclear disarmament or stop the spread of nuclear weapons.
This failure, while not unprecedented, symbolises the dysfunction in the global nuclear regime. Forty-five years since the NPT took effect and 70 years since the atomic bombings of Hiroshima and Nagasaki, more than 16,000 nuclear weapons still exist-many on Cold War-era alert, ready to launch in 15 minutes.
Meanwhile, nuclear armed countries are spending hundreds of billions of dollars on modernising their arsenals.
The NPT plays a vital role in global governance - 188 out of 193 UN member states are NPT members, and international sanctions on Iran are largely due to its non-compliance with NPT obligations.
Under the treaty, countries without nuclear weapons agree not to get them, and countries with nuclear weapons-China, France, Russia, the UK and the US-agree to get rid of them. (India, Israel and Pakistan have nuclear weapons but have not joined; North Korea withdrew from the NPT in 2003, then tested nuclear weapons.)
The NPT also affirms the "inalienable right" of states to use nuclear energy for peaceful purposes, and commits members to facilitate that access.
The main barrier to consensus in New York this month came from complex Middle Eastern dynamics.
Israel is the only country in the region with nuclear weapons, but it is not an NPT member.
For 20 years, NPT members, led by Arab countries, have called for the creation of a Middle East zone free of weapons of mass destruction, which would eventually require Israeli disarmament.
In 2010, NPT states agreed to hold a dedicated conference to discuss the Middle East zone proposal. But the US stopped the conference going ahead, to protect Israeli interests.
The same dynamic killed consensus at the Review Conference this year, the US, Britain and Canada rejecting any outcome that did not accommodate Israeli interests. In effect, non-member Israel has none of the NPT obligations of its Middle Eastern neighbours, but has a proxy veto over NPT decisions through its powerful allies and friends.
These discriminatory dynamics are indicative of fundamental challenges facing the NPT.
South Africa-the only country to have given up its own nuclear weapons-stated poignantly in the closing plenary of the Review Conference that the NPT "has degenerated into a minority rule similar to apartheid, where the will of the few will prevail whether or not it makes moral sense".
The lengthy applause for South Africa reflects a deep frustration among the vast majority of states and civil society.
This frustration is caused by the fact that while the nuclear weapon states and their allies demand ever stricter nonproliferation measures, they have failed to fulfil their nuclear disarmament obligations.
Moreover, they block all attempts to discuss, let alone negotiate, legal frameworks for disarmament. Meanwhile, nuclear risks are increasing in the modern, multipolar world, as new nuclear rivalries emerge and terrorist and cyber threats multiply existing risks.
For the 159 countries that support the "humanitarian initiative", in which New Zealand has played a leading role, the Review Conference was a chance to highlight new findings about the catastrophic humanitarian, economic, social and environmental consequences of any nuclear weapons use.
For example, atmospheric models developed by the International Panel on Climate Change show that a war using less than 1 per cent of the global nuclear arsenal would cause rapid climate change, inducing nuclear winter and crop failure, killing up to two billion people worldwide through starvation.
Additionally, though we don't yet know why, radiation disproportionately harms women and children.
Humanitarian concerns and disarmament failures have catalysed a powerful international movement to further delegitimise and stigmatise nuclear weapons.
At the time of writing, 107 countries have endorsed a Humanitarian Pledge, "to identify and pursue effective measures to fill the legal gap for the prohibition and elimination of nuclear weapons."
New Zealand has not yet endorsed this position, but it has come close.
If other countries move decisively to prohibit nuclear weapons, New Zealand will have to choose which side of history it is on.
Given the overwhelming support for nuclear disarmament among ordinary New Zealanders, there's little doubt what choice they would expect of their democratically elected representatives.
Lyndon Burford was a civil society adviser in the New Zealand delegation to the NPT Review Conference, and is a PhD candidate in international relations at the University of Auckland.