The year was 1980. The nuclear arms race had escalated for three decades. The US and the USSR had enough warheads to destroy the world several times over. The Southern California Federation of Scientists investigated the matter and produced a report called “Nuclear War in Los Angeles.”

We stacked the deck in favor of the United States. We assumed that the US struck the USSR by surprise eliminating 90 percent of the Soviet warheads in their missile silos. We analyzed a Soviet counterattack, allocating their remaining weapons to target our cities in proportion to population. LA’s share was 10 percent of the remaining Soviet arsenal.

The outcome was grim. The LA basin would instantly sustain 5 million deaths, leaving another million survivors with third-degree burns. Caltech President Marvin Goldberger contributed a foreword to our 1980 report. He said, “The important thing to note is that as horrendous as the effects described in the study are, they represent what is probably a gross underestimate of the likely outcome of a nuclear encounter.”

The report helped shape public opinion. Two years later, California voters passed Proposition 12, calling for a bilateral nuclear weapons freeze. The voters stated that a first strike was not an option.

Has anything changed?

Given the nature of today’s cantankerous debate between the leaders of several nuclear armed powers, it is useful to ask, “What has changed? And does it make a difference?”

The energy of a typical nuclear weapon is still calculated in megatons (1,000 tons) of TNT equivalent.  North Korea’s most recent test may have yielded as much as a quarter megaton — a typical thermonuclear weapon.  This could easily be scaled up to a one megaton warhead, comparable to the average warhead in our arsenal.

President Trump has threatened unilateral military action unless North Korea stops further weapons and ICBM development. What if the United States attempted a devastating first strike? How would North Korea respond?

Newsweek reported on Dec. 7 that North Korea has between 10 and 60 nuclear weapons. These warheads are undoubtedly well concealed and protected. A handful would survive a sneak attack.

Would the remaining weapons strike Seoul, Singapore, San Francisco, or Los Angeles? What would be the result?

A nuclear weapon produces three destructive effects: a blast wave, a thermal pulse, and fallout that lingers for decades.

The blast produces an atmospheric shock wave that propagates outward producing a sudden change in air pressure (measured in pounds per square inch) that crushes material in its path. According to the Department of Energy’s 1977 study, “The Effects of Nuclear Weapons,” a one-megaton weapon detonated over LA would produce a 5 psi overpressure to a distance of 4.4 miles, smashing windows of steel reinforced concrete buildings, blowing occupants through the windows and out the other side for at least 10 miles.

A nuclear weapon also releases 30 percent of its energy as thermal radiation. At the point of detonation temperatures exceed 10 million degrees Celsius — about 1,700 times that of the outer layers of the Sun. The rapidly expanding fireball easily ignites combustible materials like paper to a distance of 10 miles (remember “Fahrenheit 451?”). Human skin fries like bacon.

There would be 2.35 million instant fatalities from the blast and another million cases of third-degree burns.

Finally, large amounts of subatomic particles will be emitted from the blast, irradiating soil that is blasted into the air. The radioactive isotopes will be propagated downwind hundreds of miles as they settle back to Earth. Immediate survivors would face slow, painful death by radiation sickness within hours or days.

What has changed?

The only significant change since 1980 is the doubling of LA’s population density, increasing the lethality of any nuclear warhead. The same bleak assessment faces the inhabitants of any modern city that might be targeted. Seoul and San Francisco have population densities of about 28,000 per square mile. A counter attack would inflict 8.79 million deaths. Singapore might lose 6.46 million.

In 1953 a cease fire was achieved in the Korean War “to ensure a complete cessation of hostilities and of all acts of armed force in Korea until a final peaceful settlement is achieved.” A full peace treaty never followed. It is long overdue.

Bottom line — a first strike on North Korea must be OFF the table.

It is time to negotiate a peace treaty in Korea. 

Robert M. Nelson is a senior scientist at the Planetary Science Institute. He was a senior research scientist at NASA’s Jet Propulsion Laboratory for 34 years when he retired. In 1980, he led a team from the Southern California Federation of Scientists in a study entitled, “Nuclear War in Los Angeles”. The views expressed are his own.