US officials have been given a stark warning about the potential dangers of a nuclear

US officials have been given a stark warning about the potential dangers of a nuclear electromagnetic pulse (EMP) bomb
According to experts, such a blast could end up killing 90% of Americans indirectly by knocking out the power grid and all electrical devices within the blast radius.
Dr. William R. Graham and Dr. Peter Vincent Pry from the EMP Commission outlined to the US House of Representatives the dangers faced by a detonation - which is when a hydrogen bomb is detonated at an altitude of between 30 and 400km above a target. Such a weapon would knock out things like refrigeration for food storage, electrical lights and communication and water processing.

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"With the development of small nuclear arsenals and long-range missiles by new, radical U.S. adversaries, beginning with North Korea, the threat of a nuclear EMP attack against the U.S. becomes one of the few ways that such a country could inflict devastating damage to the United States," the pair warned in a 
"It is critical, therefore, that the U.S. national leadership address the EMP threat as a critical and existential issue, and give a high priority to assuring the leadership is engaged and the necessary steps are taken to protect the country from EMP."
Dr. Graham, a former science advisor to president Reagan and Dr. Pry, a former CIA officer, urged president Trump to prepare for a possible EMP strike.

They also warned that North Korea's weaponry is becoming more of an issue as the reclusive nation continues to schedule ICBM missile tests.
"The EMP Commission finds that even primitive, low-yield nuclear weapons are such a significant EMP threat that rogue states, like North Korea, or terrorists may well prefer using a nuclear weapon for EMP attack, instead of destroying a city."
The higher an EMP bomb is detonated, the wider the range of destruction.
At 400km (250 miles), an EMP bomb would be just under the orbit of the International Space Station and the resulting detonation would be enough to affect the majority of the US mainland.