Nuclear winter: the book in which Carl Sagan warns about the use of nuclear weapons in a war

The war between Russia and Ukraine has raised fears about the use of nuclear weapons and the consequences they could generate in the world. This is even more evident since Russian President Vladimir Putin approved a new doctrine that allows responses with these types of weapons.

The researcher Carl Sagan had already warned long before the consequences for the world in his book “A path where no man thought”, published in 1990 in collaboration with the scientist Richard Turco.

The work proposes a possible nuclear winter, an idea that began to develop in the second half of the last century due to the fear of a nuclear conflict between the two great powers of that time: the United States and the Soviet Union.

In the preface of the book they explain that in that passage of history there were estimated to be about 60,000 nuclear weapons around the world, of which about 35,000 were similar to those that destroyed Hiroshima and Nagasaki, in Japan, when American President Harry Truman ordered the bombing in 1945.

Therefore, the interest was in warning that nuclear war represented the greatest danger to humanity. “As long as there is this capacity for mutual annihilation, which is redundant and easily activated, all security guarantees will ring hollow”the authors explain in the book.

And what is nuclear winter?

It is about the effect that the use of nuclear weapons could have on the climate, a factor that is essential for life to exist on Earth. The research was the result of work with researchers Brian Toon, Tom Ackerman and Jim Pollack to calculate the effects of using these bombs.

More than fifty cases were studied in which nuclear weapons could be used, already classified as strategic and tactical nuclear weapons at that time. Of course, this is an investigation based on real and scientific data.

They point out that “In a nuclear war, powerful nuclear explosions at the surface would propel fine particles high into the stratosphere.”. The smoke that would be produced would be much more damaging than the explosions generated by the bombs themselves.

Following the logic of the greenhouse effect, dust particles found at the top of the atmosphere would reflect sunlight, preventing them from reaching the ground and initiating a cooling process. “The greenhouse effect decreases and the Earth’s surface cools much more”they say.

According to the publication, the temperature could be around 15 degrees below zero with a maximum of five degrees. This is an estimate. But, in addition to the drop in temperature, the world would also face fires, radiation and radioactive fallout. And countries that do not participate directly, in Africa, South America or Asia, would also have consequences.

“Noncombatants would face food shortages and starvation for years, all accompanied by global pandemics, especially lethal because many human immune systems would be affected by radiation”indicated Sagan and Turco.

Nuclear weapons today

After the fall of the Soviet Union, world powers reached agreements on the use of nuclear weapons and the reduction of the number of these weapons. However, these agreements have not been fully respected and there are currently nine countries with nuclear capabilities: Russia, the United States, China, France, the United Kingdom, India, Pakistan, Israel and North Korea.

The International Peace Research Institute (SIPRI) points out that until January 2024 it is estimated that there are 12,121 nuclear warheads, 9,585 are at military disposal for possible use, 3,904 are available on missiles and aircraft. On the other hand, there are also about 2,100 nuclear warheads arranged on ballistic missiles.

Regarding possession, Russia and the United States concentrate 90% of these weapons. Russia has 5,580 and the United States has 5,044. But the country that has initiated an escalation in the production of these weapons is China, going from 410 warheads in January 2023 to 500 in January 2024.

The report was published in June of this year and shows an interest among world powers in nuclear weapons. “Unfortunately we continue to see year-over-year increases in the number of operational nuclear warheads,” SIPRI director Dan Smith said at the time. With a few weeks to go until the end of the year, it seems that the trend remains the same.