Ira Helfand, MD, is co-president of International Physicians for the Prevention of Nuclear War, which was awarded the Nobel Prize in 1985. Matt Bivens, MD, is chair of Greater Boston Physicians for Social Responsibility. The opinions expressed in this commentary are theirs.

(CNN) A majority of the world's nations have just joined together to call for the elimination of all nuclear weapons. We should listen.

The United States government opposed the historic UN vote for a new treaty to prohibit nuclear weapons, but that was a knee-jerk response, grounded in last century's reflexes. Today, the path forward to total abolition of these weapons is open — even as, ironically, the danger of nuclear war is greater than it has been since the worst days of the Cold War.

The United States and Russia hold more than 90% of the world's nuclear weapons , with about 7,000 each. The other nuclear-armed states have smaller arsenals by comparison. None of the nuclear-armed states were among the 120 nations who voted to declare these weapons illegal. But if the United States is serious about seeking the security of a world free of nuclear weapons, then it should have been the first to vote "yes" on the ban.

For decades the US has instead based its security policy on the theory of nuclear deterrence — an untested belief that nuclear weapons are so terrible that they keep one nuclear-armed country from attacking any other, for fear of mutual destruction.

Perhaps. Then again, the same was said of machine guns in the 1800s — weapons of such awesome destructive power, they were predicted to end war. "They are peace-producing and peace-retaining terrors," The New York Times wrote in 1897 of the new Maxim machine guns, adding that "their devastating effects have made nations and rulers give greater thought to the outcome of war before entering."

Is there any reason to believe such tragically flawed logic from the 19th century will work out better in the 21st? More likely, nuclear weapons, those "peace-producing and peace-retaining terrors," are simply another horror that given time will grow mundane and familiar — until eventually they are used, this time perhaps in a war that destroys humankind.

That is not hyperbole. New data suggest that a war involving just 100 nuclear weapons, or less than 1% of the world's arsenals — say, for example, a regional war between India and Pakistan — would cause abrupt severe climate disruption, worldwide food shortages, hundreds of millions of starvation deaths, and probably a total collapse of civilization.

And yet we continue to base our security on these "peace-retaining terrors."

A core assumption of this deterrence theory is that the nuclear-armed states will be led by calm, collected, and well-informed people, who will infallibly respond to crises in a rational fashion.

Perhaps. Then again, as it does after every presidential election, the US has now handed control of some 6,800 warheads to a single individual. How does the current President fit with the idealized model of a world run by grownups? After all, according to a signed letter from 50 leading Republican national security experts, "He is unable or unwilling to separate truth from falsehood ... lacks self-control and acts impetuously ... has alarmed our closest allies with his erratic behavior" and overall exhibits "dangerous qualities in an individual ... with command of the US nuclear arsenal."

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It is not enough, however, to get this particularly unqualified finger off the button. We need to get rid of the button itself.

Just consider whether anyone could be calm, collected, and reasonable after, say, a nuclear explosion destroys Moscow. It might not be clear for days whether such a disaster was caused by a terrorist, a foreign power, or a domestic accident. As this was being investigated, would the world likely be dealing with a calm, matter-of-fact Russian nation? How quickly might things spin out of control?

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Yet there's no need for hypotheticals. We know of at least six incidents during and after the Cold War when either Moscow or Washington was fully prepared to fire their nuclear weapons based on an error — a mistaken belief that the other side had launched or was about to launch an attack. Six occasions when the leaders of the nuclear super powers rejected the central assumption of deterrence — that nuclear weapons are actually safe, because they can never be used — and set in motion plans to use them.

On each of these occasions the world came within minutes of nuclear destruction. It was saved mainly by chance and good luck. Our continued view of nuclear weapons as "peace-producing and peace-retaining terrors" is essentially a hope that this good luck will continue. This seems terribly naive in a world of rising tensions with Russia, and growing concern that terrorists could hack into nuclear command and control systems. The UN's nuclear ban treaty points the way to a different future, one where we eliminate all of the 15,000 nuclear weapons that threaten our survival.

The treaty is in some ways a cry of frustration from the rest of the world. The United States, Russia, and other nuclear-armed nations promised more than 37 years ago to work toward total disarmament. That was the bargain of the Nuclear Non-Proliferation Treaty: We pledged to get rid of our nuclear weapons, in return for others pledging not to seek them.

But we have not kept our promise. In fact, as approved under President Barack Obama , the US government plans to build more nuclear weapons. Current projections show that the US will spend more than $1 trillion over the next 30 years on upgrading and expanding an arsenal that is already so powerful that using only a fraction of it could destroy all life on Earth.

In recent years, international impatience with stonewalling has finally boiled over. First came a series of international conferences that cataloged the mind-numbing medical and humanitarian consequences that will follow any use of nuclear weapons. Organized by a group of non-nuclear states, and supported by the United Nations, the International Red Cross, and hundreds of medical professionals, civil society groups, and religious leaders, including Pope Francis, these discussions rejuvenated arms control efforts.

Then in the fall of 2016, the UN General Assembly upped the ante: Since the nuclear-armed states were cheating on past promises and keeping nuclear weapons, the world would now declare the weapons illegal. The United States opposed this under President Obama and that opposition has continued, but to no avail: The treaty is now entering into international law.

Yes, the United States can try to ignore this. But as with treaties banning land mines and cluster munitions, declaring nuclear weapons illegal creates a new international norm. It is also a pointed reminder that the US is long overdue to honor a legally-binding promise made 37 years ago to get rid of all of its nuclear weapons.

The new treaty is a call to action, and we should all answer it.

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In the short term, US citizens can ask our government to stand down nuclear weapons from hair-trigger alert . This can be as simple as a policy statement that, even if attacked, the US will defer any counterattack for some period of time, say 24 hours. (In an age of nuclear-armed submarines, such a de-alerting of our forces is consistent even with the flawed deterrence theories.) Citizens can also support efforts in Congress to mandate that this or any future President must get prior approval from Congress before launching a first strike with nuclear weapons — the same permission any President now must obtain before starting a war.

The next step will be to negotiate a convention among the nine nuclear-armed states to abolish these weapons, which as of today are illegal, and have always been immoral. It will not be easy. Such an abolition agreement will have to include a firm timetable for dismantling weapons, involve rigorous verification and enforcement provisions, and satisfy the legitimate security needs of concerned states from Israel to Pakistan.

There is no guarantee we will succeed in this effort. But there is no real alternative to trying, other than wishful thinking that our good luck can last forever. Until we eliminate nuclear weapons, we are living on borrowed time.