What happens if nuclear war strikes? Sun blocked, crops fail, famine unleashed

It was just a coincidence that new research on how a nuclear winter could devastate agriculture appeared around the same time The New York Times published a recent review serving as a timely reminder to read Nuclear War: A Scenario by Annie Jacobsen, a gripping and sobering non-fiction narrative published last March that imagines, in minute-by-minute detail, what could happen if a nuclear missile were launched at the United States.

Based entirely on real-world protocols, interviews with military and civilian experts and declassified documents, the author argues that nuclear deterrence is an illusion sustained by dangerous assumptions that technology is infallible, that decisions can be made perfectly under pressure and that all actors will behave rationally.

Through this realistic yet terrifying scenario, she urges readers and policymakers to recognise how little time stands between peace and unthinkable devastation and to reconsider the policies that make nuclear war possible with just one miscalculation.

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At its core, her book is a warning.

And the new scientific study published in Environmental Research Letters by researchers at Penn State University too delivers a chilling warning: a nuclear war — whether regional or global — could plunge the planet into darkness, collapse food systems and unleash unprecedented global famine.

As geopolitical conflicts intensify and nuclear sabre-rattling returns to the global stage, this research takes on urgent significance. It presents the most comprehensive modelling to date of how nuclear war could impact global agriculture by simulating how firestorm-generated soot would block sunlight, disrupt climate systems and devastate crop production.

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Soot, smoke and a shroud over the Earth

At the core of the study is the projection that soot from nuclear firestorms, particularly from burning cities and industrial areas, would be lofted into the stratosphere, forming a sun-blocking layer that could linger for years.

In the case of a large-scale nuclear conflict, such as one between the United States and Russia, sunlight reaching Earth’s surface could decline so sharply that global corn yields would plummet by as much as 80 per cent. That level of collapse would obliterate food security for much of the world.

Should we trust this study?

To understand how bad the effects could be, the researchers used a tool called the Cycles agroecosystem model. This is an advanced farming simulation developed at Penn State. It uses daily weather data, soil chemistry, how plants grow and how carbon and nitrogen interact to predict how crops will respond to different farming methods and climate conditions.

For this study, the model was adjusted to show what would happen during a nuclear winter—a time with less sunlight, colder global temperatures and more harmful UV-B rays due to damage to the ozone layer. The researchers ran the model over ten years to see how maize (corn), one of the world’s main crops, would do under these extreme conditions.

What all could happen in nuclear wars

The researchers examined six potential nuclear war scenarios, each modelled according to the amount of soot that would be released. These ranged from a 5-teragram (Tg) soot injection—representative of a regional India-Pakistan conflict—to a 150–165 Tg scenario, representing a full-scale US-Russia nuclear exchange.

The difference is vast: the global war scenario would inject 30 to 33 times more soot than the regional conflict, drastically intensifying global cooling and crop failures.

Food may become scarce

Even in the smallest modelled scenario, where about 5 Tg of soot is introduced into the atmosphere, the results are alarming. Corn yields decline globally by approximately 7 per cent, enough to strain food supply chains and cause spikes in food prices, especially in vulnerable countries with high import dependence.

The regional war scenario would still block 20 to 35 per cent of incoming sunlight and reduce global surface temperatures by 2°C to 5°C — enough to disrupt climate systems such as the South Asian monsoon, with serious consequences for rice and wheat harvests.

Under the full-scale global nuclear war scenario, however, the damage becomes existential. With 150–165 Tg of soot darkening the skies, the study predicts a catastrophic 80 per cent global decline in corn production.

This would not be a temporary setback. Nuclear winter conditions would persist for seven to twelve years, with global temperatures plunging and crop-growing seasons shortened to the point where staple crops could not mature. The sun would be blocked to such a degree that most agricultural regions would become temporarily unviable.

It could be a perfect storm

The Cycles model simulated not only cooling and sunlight reduction but also the intensification of UV-B radiation, due to ozone layer destruction from soot-induced atmospheric changes.

UV-B is known to damage plant tissues and impair growth. In the scenarios studied, UV-B peaks six to eight years after detonation, during which time even recovering climate conditions would be undermined by elevated radiation. This further reduces potential yields and delays the recovery of agricultural systems.

Why this all matters

While the seven per cent drop in corn under the India-Pakistan war model may appear modest, the global food system is tightly interconnected. A shortfall in one region — particularly in maize, wheat or rice — can ripple across continents through disrupted trade networks, hoarding, price inflation and access inequality. In the regional scenario, billions could face hunger, especially in South Asia and sub-Saharan Africa.

The 80 per cent yield loss in the full global war model, however, represents nothing short of a planetary food collapse. If other staple crops like wheat, rice and soybeans experience similar declines (as past nuclear winter studies suggest), widespread famine would become nearly inevitable. Such an outcome would overwhelm international aid systems, incite civil unrest and result in deaths numbering in the hundreds of millions, if not billions.

Seven to 12 years of darkness and hunger

One of the most startling findings is the duration of the nuclear winter effects. Unlike a temporary natural disaster, the recovery of agricultural conditions after a nuclear war would take close to a decade — or more.

The damage peaks in the early years but remains significant through year 12, meaning food systems would not have time to stabilise or self-correct. Recovery is not linear and the compound stresses of sunlight loss, UV-B radiation and global trade breakdown would delay return to normalcy.

How we can survive

The study also explores adaptation strategies that could provide some degree of protection. One approach is the use of short-season crop varieties, particularly maize types that mature quickly and are less dependent on long, warm growing seasons.

Adjusting planting calendars, improving nutrient management and selecting crop types more tolerant of cold and UV-B radiation are other possibilities. In model simulations, such adaptive measures resulted in up to 10 per cent higher yields compared to non-adaptive scenarios, especially in the post-peak years of the nuclear winter.

However, these adaptations face significant real-world barriers. Most notably, access to seeds of shorter-maturity crops and the infrastructure to distribute them would likely be disrupted in a post-nuclear world.

Recognising this, the study recommends the creation of “agricultural resilience kits” which means pre-stocked packages of adaptive seeds, tools and guidance tailored for different regions. These kits could be distributed preemptively or stored for rapid deployment after a disaster, providing a lifeline to struggling farming communities.

Maybe, it’s time for real action

The conclusion of the study is unequivocal. A nuclear war would be far more than a military or political catastrophe. It would be an ecological and humanitarian collapse. Even a limited regional exchange could trigger dangerous global agricultural shocks.

A full-scale nuclear conflict would bring about a planetary famine, with long-term consequences for civilisation itself. The Penn State researchers emphasise the importance of preparedness and diplomacy, noting that the current level of planning for such a scenario is vastly inadequate.

This study deepens our understanding of the far-reaching impacts of nuclear weapons not just in terms of immediate loss of life, but through the slow, cruel scenario of starvation and ecological collapse. It serves as a scientific imperative to reduce the risk of nuclear war and to invest in climate-resilient agricultural systems that can withstand global-scale disruptions.

People refer to Hiroshima or Nagasaki as nuclear catastrophe in wars. But that happened 80 years ago. Nuclear technology has vastly improved, and bombs become a thousand times more powerful. While some intensify nuclear sabre-rattling, the rest of the world hopes that sanity prevails as geopolitical games look increasingly chaotic.