The Washington PostDemocracy Dies in Darkness

Trump issued an executive order to prepare for an EMP attack. What is it, and should you worry?

Nah. But the U.S. should get ready for a very similar threat — from the sun.

The mushroom cloud of the first test of a hydrogen bomb, as photographed on Enewetak, an atoll in the Pacific Ocean, in 1952. (HO/REUTERS)

No, you don’t need to worry about a nuclear EMP. Here’s why.

“Only James Bond can save the world from an awesome space weapon that — in one short pulse — could destroy the earth!” That’s the plot of “GoldenEye,” in which bad guys attempt to use an electromagnetic pulse (EMP) weapon to destroy Britain’s electrical grid and send it back to the Stone Age.

President Trump believes the danger of an EMP is not just a Hollywood plot device. He recently announced an executive order meant to protect the United States from an EMP, directing federal agencies to coordinate in assessing, planning and guarding against its risks from human and natural sources.

But what is an EMP, and do we really need to worry about it? If it is a real threat, will this new executive order make a difference?

What is an EMP?

An EMP is a high-intensity surge of energy that can disrupt or destroy electronics by, essentially, overloading them. There are two ways an EMP could potentially pose a large-scale threat to U.S. security.

The first is through the detonation of a nuclear warhead at high altitude. We know this because, in 1962, the U.S. tested a nuclear bomb 250 miles above the Pacific Ocean. The test led to electronic disturbance 900 miles away in Hawaii. Specifically, streetlights were blown out, telephones went dead, and U.S., British and Soviet satellites were damaged.

The second is through a natural solar superstorm, known as a geomagnetic disturbance (GMD), which has about a 10 percent chance of occurring every decade, according to NASA. An event like this took place in 1859 and caused telegraph circuits to catch on fire.

Though an EMP is not directly harmful to people, it could lead to deaths by shutting down medical, transportation, communication, banking, finance, food and water systems. In the worst possible scenario, a large-scale EMP could have effects like Hurricane Katrina but on a national scale.

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Should you worry about EMPs? Probably not that much.

In the doomsday scenarios politicians like to talk about, an adversary like North Korea could detonate a nuclear weapon above the United States, causing an EMP to knock out the electrical grid. Theoretically, any country with nuclear weapons could do this. Fortunately, there’s little cause for concern about an EMP attack in isolation, because a nuclear EMP attack would be just that: a nuclear attack. Such brazen aggression would prompt an overwhelming — and most likely nuclear — American response. Such deterrence makes it unlikely a nuclear EMP attack would happen in the first place.

Nor is it likely that an EMP could be used to prevent U.S. retaliation, as our nuclear infrastructure is already designed to withstand such an attack. And nuclear-armed submarines deployed across the world would not be affected by an EMP directed against the continental United States.

Thus, the prospect of nuclear retaliation will almost certainly deter rival governments.

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Technical challenges make an EMP attack harder still. It isn’t clear that an EMP would have the devastating effects that some predict. Public data are scarce, but Nobel Prize-winning physicist Jack Steinberger says their destructive capacity is overstated. EMPs’ effects depend on many factors, like the altitude of detonation, the yield of the warhead and the strength of Earth’s magnetic field. This all makes it hard to predict how much damage an EMP will cause, reducing its strategic value for governments that have only one chance to inflict damage before being destroyed by the response.

Nor is it likely that terrorist groups could conduct a large-scale EMP attack against the United States. Doing so would require acquiring both a powerful nuclear warhead and a sophisticated ballistic missile able to detonate at high altitude. Governments have many reasons not to give nuclear weapons to terrorists. And if by some small chance terrorists managed to acquire such technology, would they really risk it on a relatively untested concept?

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A more likely terrorist attack scenario is via a high-power microwave (HPM) device, as this kind of weapon is relatively simple and cheap to build — the kind that’s been suspected of causing the mysterious illnesses that have struck the U.S. diplomatic staff in Havana. However, such a weapon would probably affect electronic devices within only a one-mile range and thus does not pose the strategic threat that a nuclear EMP might.

What should we be worried about? The sun.

While solar GMDs occur rarely, they can indeed interrupt power for an entire city — as happened in Quebec for nearly nine hours in 1989. That has the same kind of disruptive potential as a nuclear EMP.

How would a natural GMD blast be different from other large-scale natural disasters like a hurricane? Time. Electromagnetic incidents occur within seconds or even milliseconds over large areas of the country, the relative unpredictability of which could undermine disaster response. In areas where the power infrastructure is especially interconnected, failures could cascade.

There’s also an important difference between nuclear EMPs and solar GMDs. The former requires an attacker intent on and capable of launching such a threat. The latter is an inevitable, natural event. For a lot of reasons, governments and terrorists are highly unlikely to launch an EMP attack. Space weather events, on the other hand, happen with some regularity. The first might occur; the second eventually will.

What comes next for Trump’s EMP order?

A nuclear EMP may very well be less likely than a GMD. But either way, we don’t know whether further investments into U.S. resilience can reduce the impact. Working to better understand the hazards to U.S. infrastructure may be a good investment to evaluate if greater protection against EMPs is worth pursuing.

Will Trump’s executive order help accomplish this? Perhaps. But the burden of proof remains on the administration to demonstrate whether taxpayer dollars invested in resilience are worth taking away from other national policy priorities.

Christopher W. Blair (@cwblair10) is a PhD candidate in international relations at the University of Pennsylvania.

Casey Mahoney (@caseymahoney) is a PhD student in political science at the University of Pennsylvania and was Nunn-Lugar Fellow at the U.S. Department of Defense from 2013 to 2017.

Shira E. Pindyck (@spindyck) is a PhD candidate in international relations at the University of Pennsylvania.

Joshua A. Schwartz (@JoshuaASchwartz) is a PhD candidate in international relations at the University of Pennsylvania.