The looming shadow of nuclear winter

Imagine a world cloaked in darkness, not by night but by ash and soot from forests, fields, and cities, burning in a nuclear conflagration, which dries and cools the earth's surface and prevents the growth of crops, posing an existential threat to the remaining survivors. This isn't science fiction; it's a scientifically modeled catastrophe known as “nuclear winter”. Let us take a look back at the history of nuclear winter research, how it developed, and where it stands today.

The science behind the shadows
Intensive research on the atmospheric effects of nuclear conflict conducted by American, European, and Soviet scientists spanned the 1960s through the 1980s. In 1982, Paul J. Crutzen, who had a long-standing affiliation with IIASA starting in the 1980s and later won the Nobel Prize in Chemistry in 1995 for his work in atmospheric chemistry together with his American colleague John Birks, published a paper finding that smoke from fires generated by major nuclear exchanges would block out the sun's rays in the northern hemisphere dramatically changing the Earth's climate [1]. Consequently, in 1983, Richard P. Turco along with O. Brian Toon, Thomas Ackerman, James B. Pollack, and Carl Sagan (collectively known as the TTAPS group) using a one-dimensional radiative-convective model, demonstrated that effects will be even more dramatic with soot from cities rising into the stratosphere, causing temperature drops of more than twenty degrees Celsius, with total recovery times of no less than a year [2].

In the meantime, at the initiative of Nikita N. Moiseev, Soviet scientists were conducting their own research on nuclear detonations. Vladimir V. Alexandrov and Georgiy L. Stenchikov ran a nuclear war scenario using a three-dimensional model of the circulation of ocean and atmosphere, and the results corresponded with the conclusions of their American counterparts [3]. Joint Soviet-American research provided further confirmation of these calculations [4]. It appeared that in the massive nuclear detonation event, indirect effects will not allow crops to grow, potentially leading to global starvation, even in the areas not involved in the war. The hypothesis that life on Earth could be impossible or difficult to continue after a nuclear exchange became widely accepted by scientists at the time.

Subsequent research conducted on the topic has produced more varied results, with conclusions attempting to rename “nuclear winter” as “nuclear autumn” or “nuclear summer”, considering greenhouse effects from soot. Yet, recent work by Alan Robock et al. underscores the persistent threat: even limited nuclear exchanges could trigger devastating climatic disruptions with substantial cooling [5-6].

Nature's echoes
Atmospheric change similar to nuclear winter isn't without precedent in nature. Volcanic eruptions and wildfires demonstrate how particles can absorb solar radiation, cooling Earth's surface while warming the atmosphere [7-8]. The extinction of dinosaurs 65 million years ago offers a distant echo, where dust and darkness halted photosynthesis, leading to catastrophic climate change [9].

Beyond climate: The socioeconomic fallout
The environmental impact on human livelihoods is only part of the story. A nuclear conflict is expected to cause other far-reaching socioeconomic disruptions, such as in global trade and supply chains, leading to shortages of fuel, food, and fertilizer [10]. As IIASA researchers delve into these complexities under the Future of Life initiative, they reveal how military conflicts and political tensions can ripple through economies and ecosystems. These disruptions could alone precipitate global famine or exacerbate the environmental impacts on food production.

The team’s preliminary findings were recently presented at the European Geosciences Union General Assembly that took place in Vienna, Austria from 28 April–2 May 2025. The report conveyed three important messages.

“First, it is evident that food shortages in times of conflict affect uninvolved countries most,” says project leader Christian Folberth.  “Second, we find that non-nuclear states cannot pressure nuclear states to disarm by limiting trade as they would be the ones negatively affected. Finally, in the nuclear conflict scenario, it is apparent that even without nuclear winter effects, the world would suffer severe food shortages,” he concludes.

An abstract and a presentation on their work is available online. Stay tuned for future updates from this exciting project!

Further information
Advanced ensemble projections for indirect impacts of nuclear conflict in global food systems (ANFOS) Project page

References
[1] Crutzen, P. J., & Birks, J. W. (2016). The atmosphere after a nuclear war: Twilight at noon. Paul J. Crutzen: A Pioneer on Atmospheric Chemistry and Climate Change in the Anthropocene, 125-152.

[2] Turco, R. P., Toon, O. B., Ackerman, T. P., Pollack, J. B., & Sagan, C. (1983). Nuclear winter: Global consequences of multiple nuclear explosions. Science, 222(4630), 1283-1292.

[3] Aleksandrov, V.V. & Stenchikov G.L. (1983) On the modeling of the climatic consequences of the nuclear war. Proceedings on applied mathematics. Computer Center of AS USSR, 21 pp.

[4] Thompson, S. L., Aleksandrov, V. V., Stenchikov, G. L., Schneider, S. H., Covey, C., & Chervin, R. M. (1984). Global climatic consequences of nuclear war: Simulations with three dimensional models. Ambio, 236-243.

[5] Robock, A., Oman, L., & Stenchikov, G. L. (2007). Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences. Journal of Geophysical Research: Atmospheres, 112(D13).

[6] Robock, A., Toon, O. B., Bardeen, C. G., Xia, L., Kristensen, H. M., McKinzie, M., et al. & Turco, R. P. (2019). How an India-Pakistan nuclear war could start—and have global consequences. Bulletin of the Atomic Scientists, 75(6), 273-279.

[7] Robock, A., & Mao, J. (1995). The volcanic signal in surface temperature observations. Journal of Climate, 8(5), 1086-1103.

[8] Shaparev, N., Tokarev, A., & Yakubailik, O. (2024). Cold Traces of Smoke from Wildfires in the Environment. Environmental Processes, 11(1), 5.

[9] Toon, O. B., & Robock, A. (2025). Earth in Flames: How an Asteroid Killed the Dinosaurs and How We Can Avoid a Similar Fate From Nuclear Winter. Oxford University Press.

[10] Jägermeyr, J., Robock, A., Elliott, J., M ller, C., Xia, L., Khabarov, N., Folberth, C., Schmid, E., Liu, W., Zabel, F., Rabin, S.S., Puma, M.J., Heslin, A., Franke, J., Foster, I., Asseng, S., Bardeen, C.G., Toon, O.B., Rosenzweig, C. (2020). A regional nuclear conflict would compromise global food security. PNAS 117, 7071 7081. https://doi.org/10.1073/pnas.1919049117

Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.