Subsequent modelling starting in 2007 using modern computers lowered this threshold dramatically: Rather than the hundreds or thousands of nuclear explosions which TTAPS and other researchers originally believed necessary to trigger the nuclear winter phenomenon, it became clear that 100 Hiroshima-sized explosions (~15 kilotons) over urban areas would be sufficient to trigger the deaths of billions of people (https://www.giss.nasa.gov/pubs/abs/xi08000i.html).

This presents an irreducible problem for advocates of nuclear deterrence: Any nuclear conflict which approaches the aggregate of 1.5 megatons over urban targets is likely to trigger unacceptable GLOBAL casualties — innocent civilians from the other side of the world who have nothing to do with the conflict in question. Strategically, this represents an even greater nightmare than “standard” nuclear attack planning: What to do if the enemy explodes ~1 megaton of nuclear weapons over your cities? Retaliate, and risk laying waste to large swaths of humanity and civilization?

It is clear to those who have eyes to see that the only rational future for nuclear deterrence (that is, the only applicable logic) is, in the short term, self-deterrence, and, on an urgent basis in the longer term, total nuclear disarmament.

Some other thoughts:

>Although there are notable breakthroughs in efforts to reach agreements on arms control and disarmament, the world remains far from achieving disarmament goals and is still on a long quest to eliminate nuclear weapons. Nuclear weapons hold a key place in security policy.

See above. Nuclear weapons can have no legitimate place in any rational policy-making.

>The latest report by the Stockholm International Peace Research Institute (SIPRI) says nearly all nuclear-armed states, including the United States, the United Kingdom, France, Russia, China, India, Pakistan, Israel, and North Korea, are modernizing and upgrading their nuclear capabilities.

The disarmament community, including SIPRI, bears an enormous responsibility here: To bring the basic facts of nuclear winter to the attention, not only to the rulers of the nuclear weapons states, but to all eight billion of Earth’s inhabitants.

>Consequently, a perilous new nuclear arms race is emerging, and reliance on nuclear weapons is increasing. This inevitably raises the question, is nuclear disarmament still logical and relevant?

See above. Total nuclear disarmament is the only logical response to the status quo; nothing else is relevant, including most of the disarmament community’s actions.

>Under the NPT, the division between nuclear weapons states and non–nuclear weapon states is not supposed to be permanent as all NPT parties will move to non–nuclear weapon states.

True, but irrelevant. Proliferation is not the real danger here, as far more nuclear weapons exist than are needed to trigger nuclear winter. What has changed is that India and Pakistan are now capable of killing billions globally with no “assistance” from anyone else: not Beijing, not Moscow, not Washington.

>The current geopolitical landscape regarding nuclear proliferation, nonproliferation, counter-proliferation, and disarmament indicates a deadlock in the pursuit of a global zero (GZ). Two key terms, conceptualized in this article, may help explain the shortcomings in nuclear disarmament efforts under the grand bargain. The first is the security betrayal trap (SBT), which refers to a situation where security guarantees are betrayed, leaving a country exposed and vulnerable. The second is disarmament deception syndrome (DDS), a pattern of negative consequences resulting from false promises made during the disarmament process.

Utterly irrelevant. The cold equations of nuclear winter don’t care about national pride, betrayals or truth-telling.

>Ukraine regrets abandoning its inherited nukes in the wake of its ongoing war with Russia. The withdrawal of North Korea from the NPT and the lesson it learned are that nukes are key to national survival. Similarly, Iran’s pursuit of nuclear capability is considered inevitable for the country’s national security. In this geopolitical context, it is hard to make countries believe in any negative as well as positive security in return for disarmament and de-nuclearization.

Completely, utterly, totally irrelevant. More players in the nuclear winter sweepstakes simply mean more education required on the implications of the cold, dark equations.

>Disarmament is also unlikely in today’s world due to the changing technological landscape.

Irrelevant and ultimately wrong-headed. There is only one choice possible on global nuclear disarmament, and that is to save civilization.