Part 7: Can nuclear weapons cause a catastrophic climate event?

The immediate consequences of nuclear war would be catastrophic and on a scale unknown in human history. Those consequences include millions of civilian deaths, radioactive contamination, fire storms, as well as global economic and social devastation.

These almost unimaginable results have been long known to governments. In fact, it is the capability of producing unprecedented destruction that makes nuclear weapons different from previous weapons technologies built by humans.

But in 1945, when nuclear weapons were used against Japan, there was no developed climate science. At the first nuclear test in New Mexico, physicists jokingly took bets on whether the test would ignite the atmosphere, but little was known about the chemistry or physics of the atmosphere and the oceans.

Over the decades, scientists have attempted to model a nuclear war’s possible climate and environmental consequences. The most famous example is Carl Sagan’s concept of a “nuclear winter,” in which a nuclear war might cause enough soot and particles to be injected into the atmosphere to partially block the sun.

The “nuclear winter” thesis has been the subject of intense scientific debate that has evolved over the decades. It fell out of favor following Iraq’s invasion of Kuwait in the early 1990s, when the massive oil fires started by Iraqi troops did not have the impact nuclear winter modelers expected.

More recently, research into the possible environmental effects of nuclear war has been revived as new techniques and a new generation of scientists have returned to the question. The research looks at various potential environmental impacts, including the effects of nuclear war on sunlight, the ozone layer, the chemistry of oceans, and other environmental effects.

Studying the potential consequences of a nuclear war is challenging. Nuclear war and the environment are exceedingly complex topics, and there is much uncertainty (because, luckily, we do not have a lot of experience with nuclear wars). Despite those difficulties, scientists have pushed forward.

Current research suggests that a nuclear war could, in fact, harm the environment with potentially catastrophic consequences for millions of people far from the actual war itself. Given the complexity of the subject, these are tentative conclusions, but it appears that it is a real possibility.

Our understanding of the consequences of a nuclear war on the climate and the environment will advance substantially in the coming months. The National Academies, America’s most prestigious scientific body, will release a new report, Independent Study on Potential Environmental Effects of Nuclear War. This study will “consider non-fallout atmospheric, terrestrial, and marine effects and their consequences, including changes in climate and weather patterns, airborne particulate concentrations, stratospheric ozone, agriculture, and their impacts on ecosystems.”

If the Academy’s report concludes that there is a risk of a global environmental catastrophe from even a “limited” or regional nuclear war, it may require that governments alter their understanding of nuclear deterrence. A nuclear war between two countries, say India and Pakistan, could devastate other countries not directly involved in the war. It would also mean that America’s nuclear weapons cannot defend the US from other countries fighting their own nuclear war. In short, it may be that a nuclear war anywhere is a threat to everywhere.

It is unlikely that we will definitively know nuclear war’s consequences for the climate without observing an actual nuclear war, but our understanding of the potential danger may be sufficient, and the consequences so horrific, that governments can reasonably take action now before the models become reality.