Biggest Threats to U.S. Are Nuclear War With Russia, Biological Attack and Climate Change, Former Spy Chief Says

A Yars RS-24 intercontinental ballistic missile system is seen during the 72nd anniversary of the end of World War II on Red Square in Moscow on May 9. Yuri Kochetkov/Pool/Reuters

The three most immediate threats to U.S. national security are a potential nuclear war with Russia, a biological attack and climate change, according to a former CIA chief.

Michael Morell, who served as acting CIA director for about two months in 2011 and about four months ending in March 2013, said the deteriorating state of U.S. politics is what scares him the most in the long term, but saw "only three" immediate existential threats to the country.

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"The first is a nuclear exchange with Russia. That could destroy the United States. The second is a naturally occuring or man-made biological agent that kills 60, 70 percent of the population...We don't spend enough time on that," Morell told the Pod Save the World podcast Thursday.

"And then the third—and some people may laugh at this, but it's absolutely true—the third is climate change. It's an existential threat to the United States of America," he said.

A Yars RS-24 intercontinental ballistic missile system is seen during the 72nd anniversary of the end of World War II on the Red Square in Moscow, on May 9. Russia has the world's largest stockpile of nuclear weapons. Yuri Kochetkov/Pool/Reuters

Morell, who also mentioned "terrorists with nuclear weapons" as a potential doomsday scenario that keeps him up at night, briefed President George W. Bush in the aftermath of the 9/11 attacks in 2001, correctly pinning the world's deadliest act of terrorism on Osama bin Laden and Al-Qaeda. Morell would later go on to advise President Barack Obama on the hunt for, and ultimate killing of, bin Laden in 2011.

While claiming to have no particular political affiliation, the veteran intelligence analyst criticized Donald Trump's campaign for the presidency, writing in a New York Times editorial in August 2016 that he was "not only unqualified for the job, but he may well pose a threat to our national security." Morell has spoken ominously of the Trump administration's polarizing decisions since then.

"The thing that worries the most is the politics in my own country, is the failure of our politics to have our political leadership come together, make compromises that advance our economy and our society," Morell said during Thursday's podcast.

"At the end of the day, [the] most important determinant of a country's national security is the health of its economy and the health of its society, and the thing that scares me the most in the long term is the state of our politics here,'s gotten worse, it hasn't gotten better," he continued.

Michael Morell, former director of the Central Intelligence Agency, attends the annual Allen & Company Sun Valley Conference in Sun Valley, Idaho, on July 6, 2016. Drew Angerer/Getty Images

As the U.S. approaches the one-year mark of Trump's shock victory in the 2016 presidential race, the country's relationship with Russia has yet to significantly improve as the Republican leader had promised. While the two countries have begun cooperating in Syria, they continue to militarize their defenses across Europe, where NATO and Moscow are undergoing the largest arms race since the Cold War.

The Russian military tested its strategic nuclear forces Thursday in a series of four ballistic missile launches across the country. The drills, in which Russian President Vladimir Putin himself participated, also saw warplanes blasting targets in western Russia.