Almost everyone knows the acronym “EMT.” We know that emergency medical technicians will arrive in a hurry if someone calls for an ambulance. Less familiar is the acronym “EMP.” But if an electromagnetic pulse were to hit the United States, we would need a lot more than an ambulance to fix the problems that would result.

That’s because an EMP is a high-intensity burst of electromagnetic energy that causes severe current and voltage surges. The result: All electronic devices within the line of sight would be burned out. Cellphones and microwaves, along with all the other devices we use in our daily lives, would be toast.

How big a line of sight are we talking? A single EMP could, in a flash, shut down the entire power grid and transportation systems over a large region of the country. Tens of millions of Americans suddenly would find themselves in an inconvenient situation that also is life-threatening.

EMPs have two basic causes: One is natural. They can be generated by geomagnetic storms, or “space weather.” A solar flare can cause one. The other cause is man-made nuclear and radio-frequency weapons. A nuclear warhead detonated at the right altitude could put you back about two centuries in a hurry. A lot of people would wind up wishing they had an old-fashioned backyard bomb shelter.

Sound overblown? According to some critics, yes. To New York Times reporter William J. Broad, the EMP threat is “science fiction.”

Tell that to the congressionally mandated Commission to Assess the Threat to the United States from Electromagnetic Pulse Attack. Its members called a high-altitude nuclear EMP one of the few ways an enemy could inflict catastrophic damage on the United States.

“The Commission’s report is no exercise in science fiction,” writes Heritage nuclear analysts James Carafano and Owen Graham. “It presents the consensus view of the defense and intelligence communities, as well as the nuclear weapon labs. These sober national security experts don’t use the word ‘catastrophic’ lightly.”

They are not alone. A second commission, the Congressional Commission on the Strategic Posture of the United States, independently re-examined the EMP threat and reached the same conclusion. No fewer than five bipartisan commissions and independent U.S. government studies have made it clear that an EMP would place our critical infrastructure and by extension, the American people at great risk.

What is the most effective way to get a nuclear weapon to a position where it can be detonated to create an EMP? Where it can cause maximum damage to the U.S. electrical grid and other elements of our infrastructure? A ballistic missile. What are rogue nations such as North Korea trying to acquire? Ballistic missiles.

This is one of the reasons it’s crucial that we get serious about building a comprehensive missile defense.

The Obama administration has taken one important step. In the wake of North Korea’s most recent (and particularly bellicose) round of saber rattling and missile testing, it has reversed its policy to cut missile defense interceptors in Alaska. Those interceptors now are back in the budget.

There is a lot more we can be doing to protect ourselves, though. We have a rudimentary missile defense in place, but we need a network with land, sea, air and space capabilities. That means locating sensors throughout the world and in space. It also means increasing the number of interceptors we have to counter long-range missiles. With a layered system, we have a much better chance of destroying an incoming missile.

It might be tempting to dismiss North Korea’s threats as just talk, but as Korea analyst Bruce Klingner notes: “It’s talk until it happens. We thought it was just talk until they sank a South Korean ship in South Korean water. We thought it was just talk until they shelled a South Korean island.”

We have the technological know-how and capability to do more than hope for the best. Why take the chance?

-Ed Feulner is the former president of the Heritage Foundation.