How well would the modern world hold up in a nuclear war? According to new research, not well at all; such an event would be “globally catastrophic”.

With a war ongoing in Eastern Europe in which one participant possesses nuclear weapons, the possibility that such weapons would be used is more real and worrying than it’s been in several decades. And we all know that an escalation of hostilities to include such weapons would have a huge impact on life as we know it.

But exactly what would this impact be? A new study led by Cheryl Harrison, an Assistant Professor at the Louisiana State University Department of Oceanography & Coastal Sciences estimates the effects a nuclear conflagration would have on the Earth’s weather and climate patterns, and what societies would have to face because of them.

Atom-splitting fire

“It doesn’t matter who is bombing whom. It can be India and Pakistan or NATO and Russia. Once the smoke is released into the upper atmosphere, it spreads globally and affects everyone,” said Harrison, who has a joint appointment at the LSU Center for Computation & Technology.

“Nuclear warfare results in dire consequences for everyone. World leaders have used our studies previously as an impetus to end the nuclear arms race in the 1980s, and five years ago to pass a treaty in the United Nations to ban nuclear weapons. We hope that this new study will encourage more nations to ratify the ban treaty,” said co-author Alan Robock, distinguished professor in the Department of Environmental Sciences at Rutgers University.

The study ran multiple computer simulations taking into account which countries have nuclear arsenals at their disposal and the known number of such weapons that are available. These simulations looked at the end result that regional- or larger-scale nuclear exchanges would have on various natural systems on Earth. Today, 9 nations can call upon more than 13,000 nuclear weapons, according to the Stockholm International Peace Research Institute.

In all of the scenarios that the team ran, the detonations produced by nuclear weapons would lead to the release of soot (black carbon) and smoke into the higher atmosphere. These particles would then absorb sunlight needed on the surface, leading to widespread crop failure around the world.

The situations that the team simulated included a nuclear exchange between the U.S. and Russia, which involved 4,400 100-kiloton nuclear weapons aimed primarily at population centers and industrial areas. This war resulted in 150 teragrams — over 330 billion pounds — of smoke and soot being injected into the upper atmosphere. A more ‘modest’ war, modeled on an exchange between India and Pakistan that involved about 500 100-kiloton nuclear weapons. This one generated 5 to 47 teragrams — 11 billion to 103 billion pounds — of smoke and soot.

In the first month after these exchanges, the team explains, the average global temperature would drop by around 13 degrees Fahrenheit (roughly 7 Celsius). This would be a more dramatic temperature change than the one experienced during the last Ice Age.

Ocean temperatures would drop quickly and would not return to their pre-war baseline even after the smoke and soot cleared. These lower temperatures would cause sea ice to expand by over 6 million square miles (roughly 16 million sq kilometers) worldwide, reaching thicknesses of up to 6 ft (1.8 m) in some major basins. This ice would completely block several of the world’s major ports including Tianjin, Copenhagen, and St. Petersburg. Since major port regions are normally ice-free, most ships today are not designed to contend with sea ice. Essentially, a nuclear war would quickly make it impossible for global trade as it is today to continue

The war in Ukraine and the pandemic before it have already shown how fragile the world’s trade networks are to major shocks, and how much a perturbation of supply in one area of the world can disrupt all others.

But trade would not be our greatest concern after such a war, the team explains. The drop in ocean temperatures would lead to the widespread death of marine algae from the Arctic to the North Atlantic and North Pacific oceans. Since these form the foundation of marine food chains, such a die-off would create a massive famine in the world’s oceans with extremely dire consequences for wildlife. Fishing and aquaculture would grind to a halt, cutting us off from what has been a cornerstone food source throughout history. The wider environmental implications of this die-off are too great to accurately estimate.

“The current war in Ukraine with Russia and how it has affected gas prices, really shows us how fragile our global economy and our supply chains are to what may seem like regional conflicts and perturbations,” Harrison said.

One interesting finding of the study is that the clouds of particles released in the upper atmosphere by volcanic eruptions could lead to the same effects as those seen in the team’s simulations. This aligns well with historical data showcasing the environmental changes observed following such eruptions.

“We can avoid nuclear war, but volcanic eruptions are definitely going to happen again. There’s nothing we can do about it, so it’s important when we’re talking about resilience and how to design our society, that we consider what we need to do to prepare for unavoidable climate shocks,” Harrison said. “We can and must, however, do everything we can to avoid nuclear war. The effects are too likely to be globally catastrophic.”

One of the last tidbits of information that the paper offers is that marine ecosystems took longer to recover than those on land following a nuclear exchange. This would be due to the extreme level of disruption such ecosystems would experience due to both the initial exchange, as well as the long-term impact to the global natural balance.

In the largest exchange scenario (US-Russia), ocean recovery took decades at the surface but hundreds of years at depth. Meanwhile, changes to Arctic sea ice lasted thousands of years — a nuclear exchange would effectively create its own little ice age.

The paper “A New Ocean State After Nuclear War” has been published in the journal AGU Advances.