Thirty-three minutes. That’s all the time we’d have to respond to an incoming intercontinental ballistic missile from anywhere in the world.

Roughly half an hour to avert disaster — if we’re lucky.

Sure, that isn’t the most cheerful thought to entertain, especially at Christmas time. But with all the saber-rattling coming from North Korea these days, not to mention other global hot spots, we don’t have the luxury to pretend this threat doesn’t exist.

A successful nuclear strike would carry an unthinkable toll. The bomb the U.S. dropped on Hiroshima, Japan, in 1945 had an explosive yield of 15 kilotons of TNT. North Korea’s nuclear test in October? 250 kilotons.

According to the documentary film “33 Minutes,” the Sept. 11 attacks resulted in 3,000 deaths and $80 billion in damage. A nuclear bomb dropped on Manhattan would cause hundreds of thousands of casualties, and trillions in damage.

That’s not the only way a nuclear bomb could be used against the U.S., however. An electromagnetic pulse, or EMP, is another likely method of attack. In this case, a nuclear bomb isn’t dropped on the targeted area, but detonated hundreds of miles above it. This would emit a wide-ranging burst of electromagnetic radiation.

Goodbye, electric grid. Nearly everything powered by electricity, from telephones, internet service and electric power, to car batteries and airplane controls, would be disrupted or permanently damaged. And not just in one city, but across the continental United States. In a flash, we’d be set back more than a century.

But wait, you may be thinking. You said we’d have 33 minutes to respond. We could counteract such an attack, right? Stop it from happening?

If you’re thinking of missile defense, you’re right. We do have a way of responding, and we could stop a missile with a missile. That’s the good news.

The bad news is that the missile-defense system we have isn’t as comprehensive and well-developed as it could and should be at this stage. We have a revolver, when we could have an automatic rifle.

Nearly 35 years ago, President Reagan first called for a way to render the threat of ballistic missiles “impotent and obsolete.” Yet today, thanks in part to opposition from those who consider missile defense both unworkable and destabilizing, we have only one system capable of shooting down long-range ballistic missiles headed for the U.S. homeland: the Ground-Based Midcourse Defense (GMD) system.

We can do better, though. The GMD system is the only system we have capable of intercepting an ICBM in the mid-course phase of its flight. With a system that includes sea- and space-based interceptors, we could target ICBMs earlier in their flight — during the boost or ascent phase, when they’re traveling more slowly and are easier to hit.

Now’s the time, as the Trump administration conducts its own missile-defense review, to reverse the cutbacks that occurred under the Obama administration. Defending ourselves on the cheap is unwise. With the right budgetary priorities, we can ensure that we get more than one shot at destroying an incoming missile.

North Korea, after all, isn’t the only threat (as if it wasn’t enough). Iran has a large ballistic missile arsenal and an active nuclear program, and it remains a dogged opponent of U.S. interests in the Middle East.

Then there’s our old Cold War nemesis, Russia. Thirty years ago, it signed the Intermediate-Range Nuclear Forces (IMF) Treaty with the U.S. But “Russia has violated the treaty at least twice,” writes defense expert Michaela Dodge. “The U.S. government’s 2017 report identifies a Russian ground-launched intermediate-range ballistic missile 3N-14 that can potentially carry a nuclear warhead.”

President Trump has called the tax-cut bill before Congress “a big, beautiful Christmas present” for the U.S. With the work of the administration’s ballistic-missile defense review coming shortly thereafter, what better way to follow up this gift than to make 2018 the year when we finally get serious about protecting ourselves?