This article was originally published by the Christian Science Monitor.

David KriegerPresident Obama and other world leaders gathered at the Nuclear Security Summit in Seoul, South Korea, this week to address threats posed by unsecured nuclear material. If Mr. Obama is truly concerned about nuclear safety, he should seriously consider doing away with the 450 inter-continental ballistic missiles deployed and ready to fire at Russia on a moment’s notice.

Last month we were among 15 protesters who were arrested in the middle of the night at Vandenberg Air Force Base, some 70 miles north of Santa Barbara, Calif. We were protesting the imminent test flight of a Minuteman III inter-continental ballistic missile.

The Air Force rationale for doing these tests is to ensure the reliability of the US nuclear deterrent force; but launch-ready land-based nuclear-armed ballistic missiles are the opposite of a deterrent to attack. In fact, their very deployment has the potential to launch World War III and precipitate human extinction – as a result of a false alarm.

We’re not exaggerating. Here’s why: These nuclear missiles are first-strike weapons – most of them would not survive a nuclear attack. In the event of a warning of a Russian nuclear attack, there would be an incentive to launch all 450 of these Minuteman missiles before the incoming enemy warheads could destroy them in their silos.

If the warning turned out to be false (there have been many false warnings), and the US missiles were launched before the error was detected, World War III would be underway. The Russians have the same incentive to launch their land-based missiles upon warning of a perceived attack.

Both US and Russian land-based missiles remain constantly on high-alert status, ready to be launched within minutes. Because of the 30-minute flight times of these missiles, the presidents of both the US and Russia would have only approximately 12 minutes to decide whether to launch their missiles when presented by their military leaders with information indicating an imminent attack (after lower-level threat assessment conferences).

That’s only 12 minutes or less for the president to decide whether to launch global nuclear war.  While this scenario is unlikely, it is definitely possible: Presidents have repeatedly rehearsed it, and it cannot be ruled out due to the graveness of its potential consequences.

Russia came close to launching its missiles based on a warning that came Jan. 25, 1995. President Yeltsin was awakened in the middle of the night and told a US missile was headed toward Moscow. Fortunately, Yeltsin was sober and took longer than the time allocated for his decision on whether to launch Russian nuclear-armed missiles in response.

In the extended time, it became clear that the missile was a weather sounding rocket from Norway and not a US missile headed toward Moscow. Disaster was only narrowly averted.

Here is the really compelling part of the story: If all 450 US land-based Minuteman III missiles with thermonuclear warheads were ever launched at Russia – with many of the targets in or near cities, as now planned – most Americans would die as a result, along with most of humanity.  Our own weapons would contribute as much or more to these deaths in America and the rest of the globe as any Russian warheads launched.

This is because smoke from the enormous nuclear firestorms created by even a “successful” US nuclear first-strike would cause catastrophic disruption of global climate and massive destruction of the Earth’s protective ozone layer, leading to global famine.

Recent peer-reviewed studies, done by atmospheric scientists Alan Robock (Rutgers), Brian Toon (University of Colorado-Boulder), Richard Turco (UCLA) and colleagues, predict that such an attack would create immense firestorms that would quickly surround the planet with a dense stratospheric smoke layer.

The black smoke would be heated by the sun, lofted like a hot air balloon, and would remain in the stratosphere for at least 10 years. There it would block and prevent a large fraction of sunlight from reaching the Earth’s surface. The sharp reduction of warming sunlight would rapidly produce global Ice Age weather conditions. This would eliminate or dramatically reduce growing seasons for a decade and would likely cause the starvation of most or all humans.

Along with other effects – including prolonged destruction of the ozone layer – most complex life on Earth could be destroyed. Scientists say the process would be similar to when an asteroid hit the Earth some 65 million years ago, raising a global dust cloud that reduced sunlight, lowering temperatures and killing vegetation. That caused the extinction of the dinosaurs and 70 percent of the Earth’s species.

The cause of extinction in our case would not be an external, celestial event, but rather the launching of thermonuclear weapons we had created by our own cleverness, supposedly for our own security.

The Minuteman III missile tests from Vandenberg Air Force Base are thus really tests of an American Nuclear Doomsday Machine.

Nuclear weapons do not make the US or the world more secure. In particular, the Minuteman III missiles – land-based, vulnerable, on high alert, and susceptible to being triggered by a false alarm – make us less secure. Anyone who cares about humankind having a future should protest these tests and call for the elimination of all nuclear-armed inter-continental ballistic missiles as an initial step toward the total abolition of nuclear weapons.

If the US did away now with its nuclear-armed land-based missile force, it would still have 288 invulnerable submarine-launched ballistic missiles (armed with approximately 1,152 warheads) to act as a retaliatory threat to nuclear attack. But it would no longer have tempting targets for the Russians to strike preemptively in a time of tension or in the event of a false warning of attack.

It would still be imperative to reduce US (and Russian) total warheads to levels that do not threaten the possibility of causing human extinction.

And even the smaller existing nuclear arsenals of India and Pakistan threaten global disaster. Professor Robock and his colleagues have estimated that in a nuclear exchange between India and Pakistan in which each side used 50 Hiroshima-size bombs (each side now has more than that number), the smoke rising into the stratosphere could cause a global reduction of sunlight and destruction of ozone leading to crop failures and global famine.

By comparison, the launch-ready thermonuclear forces of the US and Russia contain roughly 500 times the explosive power of the 100 atomic bombs of India and Pakistan.

Now is the time for the people and nations of the world to stand up against the potential extinction of the human species and demand that political leaders pursue the path to zero nuclear weapons, a path mandated by the terms of the Nuclear Non-Proliferation Treaty and the International Court of Justice. Until then, protest and civil resistance will be necessary.

We should seek two principal goals: first, a commitment by the existing nuclear weapon states to forego launch-on-warning and first use of nuclear weapons under any circumstances; and second, good faith negotiations for a new treaty for the phased, verifiable, irreversible, and transparent elimination of nuclear weapons.

It is our hope that by committing nonviolent civil resistance, being arrested, going to federal court, and explaining our actions to the public, we will help to awaken and engage the American people on this issue of utmost importance to our common future.