Nuclear war, nuclear winter, and the food system: A contribution to the United Nations Independent Scientific Panel on the Effects of Nuclear War

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This post was originally an invited contribution to the United Nations Independent Scientific Panel on the Effects of Nuclear War. I’m also sharing it here as an overview of the current state of nuclear winter research (+ related topics) and the open questions the field is grappling with. It was written by me with extensive input from the team at the Alliance to Feed the Earth in Disasters (ALLFED), whose comments and suggestions greatly improved it.

The research around the impacts of nuclear war began with immediate effects such as explosions and fallout. A vast literature exists and has been building since the mid-20th century. The literature around the climatic effects is smaller, partly because the climatic effects were only scientifically recognized in the early 1980s (Turco et al., 1983), but also due to nuclear winter research being partly defunded in the late 1980s and 1990s (Turchetti, 2021) and because general interest declined after the dissolution of the Soviet Union in 1991. There have been some studies in the intervening decades, but scientific attention increased again after several philanthropically funded studies used modern climate models and provided the data for other researchers to build on (Robock et al., 2023). After the Russian invasion of Ukraine, the topic also gained more attention in public and policy discussions (Helfand et al., 2022). The body of research has been growing since then, albeit slowly due to funding constraints, yet many questions around nuclear war and subsequent nuclear winter remain unanswered. Below, I summarize the current state of knowledge, focusing on climate, the food system, and where gaps exist.

The climate aspect of nuclear war has been explored extensively in comparison to other aspects. Beginning with the original nuclear winter study (Turco et al., 1983), the literature progressed through intermediate studies (e.g. Robock et al. (2007) to more recent studies that provided the data for the reemergence of the field (Coupe et al., 2019; Toon et al., 2019). These were used for a set of papers that explored facets of post-nuclear war climate, such as UV radiation changes (Bardeen et al., 2021), the state of the ocean (Harrison et al., 2022), and the emergence of a so-called Nuclear Niño (Coupe et al., 2021). More recently, there has been a push to make this data more accessible to enable further study (Harrison et al., 2025).

What has become clear from nuclear winter climate research is that the climate impacts of a nuclear war would be significant, and would lead to abrupt cooling (beginning within weeks and reaching its lowest values 2–3 years after the war), and global effects (impacting both Hemispheres) (Coupe et al., 2019). Some research disputes the severity of these effects from US national laboratories like Los Alamos (Reisner et al., 2018). However their data and code are not easily available, which prevents independent researchers from reproducing their calculations (Robock et al., 2019).

Constraints on the scientific discussion around climate and nuclear winter research include that the number of studies remains limited and concentrated among a small number of researchers, and many rely on the same underlying modelling data. Moreover, the group around Alan Robock that conducted much of this research has been criticized for overly pessimistic assumptions (Reisner et al., 2019). The debate around this is summarized in Hess (2021). Given these dynamics, a Coupled Model Intercomparison Project (CMIP)—but for nuclear winter instead of global warming—or, at minimum, several attempts to reproduce the climate simulations using other models, could provide a more robust foundation for future research.

Building on the data from nuclear winter climate research, a significant number of studies explore the food system and how it might react to the sudden shift in climate following a nuclear war. For example, Jägermeyr et al., (2020) estimate that even a limited nuclear war would have major consequences for agriculture, primarily due to a reduction in temperatures, precipitation and sunlight. There is also research that studies the impacts of increased UV radiation on agriculture, though this impact seems to be constrained to the most severe scenarios (Shi et al., 2025). Importantly, the food system impacts would not be limited to the combatant nations, nor even to the hemisphere in which the war occurred. In addition to climate effects on agriculture, countries would likely also face a cascading disruption of trade systems (Jehn, Gajewski, et al., 2025) and the countries which are hit by nuclear weapons would see their industrial production plummet (Blouin, Jehn, et al., 2024). Besides many other negative impacts, this would decrease availability of fertilizer and pesticides, which would impact yields beyond the climate impacts (Moersdorf et al., 2024).

Xia et al. (2022) used a comprehensive model of the food system to explore how many people globally would be affected by famine after nuclear war, arguing that the death toll from famine could be higher than direct fatalities from the nuclear war. This result assumes that global food trade would cease completely and that adaptation would be limited. Other research that models continued trade alongside large-scale and rapid adaptation concludes that many— potentially even all of these famine deaths—could be preventable given significant international cooperation, technological responses, and food aid (Rivers et al., 2024). However, further studies into trade show that there would be severe disruptions in the trade system, even in smaller nuclear exchanges (Jehn, Gajewski, et al., 2025). Together, these findings show that the food system’s response to a nuclear war is not fully understood.

We now know that inaction following a nuclear war would lead to widespread famine, while rapid and large-scale interventions could prevent it. However, research that explores the factors that make these outcomes—or the paths between them—more or less likely is missing.

Another major gap is an assessment of how plants would grow under nuclear winter conditions. Crop models are not calibrated to the estimated nuclear winter light conditions. Growth chamber trials are currently in progress, led by researchers at the Pennsylvania State University and Alliance to Feed the Earth in Disasters (ALLFED), but they are not yet complete and will represent only a first data point. Pilot-scale field trials that simulate sets of possible nuclear winter conditions would be a valuable next step towards high-quality evidence and would reduce uncertainty.

The longer term effects of nuclear war will crucially depend on responses and adaptations of the food system. ALLFED has contributed to research on the effects of nuclear war on food systems, including how different adaptation pathways could shape societal consequences in the years and decades following a nuclear war. Much of this work focuses on resilient food solutions, defined as food sources that could compensate for severe global shortfalls in traditional food production, such as those caused by a nuclear winter (see García Martínez et al. 2025, for a comprehensive review). Examples include crop relocation (Blouin et al., 2025), seaweed (Jehn et al., 2024), greenhouses (Alvarado et al., 2020), and single-cell protein grown in bioreactors (García Martínez et al., 2022). Without minimizing the profound and catastrophic consequences of nuclear war, this research is intended to support preparedness and informed decision-making, and is also relevant to strengthening resilience to other global food shocks.

In the past, research on resilient foods has focused primarily on modelling and the initial exploration of the research landscape. This work suggests that there is nothing in physics or current technology that would prevent humanity from producing enough food in a nuclear winter; rather, the main challenges lie in distribution, trade, and coordination—that is, in the systems required to rapidly scale and distribute resilient foods.

However, this part of the research landscape is almost completely unexplored. There are no clear ideas for how trade and cooperation could be maintained following a nuclear war, yet understanding this would be essential to increasing resilience for non-combatant countries. Without this understanding, there is a high chance that cascading trade bans could shut down global trade and lead to famine. On a much smaller scale than would be expected following a nuclear war, there were comparable dynamics during the 2007–2008 rice crisis. This highlights a range of questions that are primarily political. How would remaining food be distributed? What measures could food-importing countries take to address international supply shortages? How would emergency decisions be made when every delay leaves more people hungry? These questions require answers before a nuclear war, not after.

What also becomes clear from the literature is that many of the negative consequences of a nuclear war have not been examined yet. For example, a recent study explored the consequences of increased frost depths after a nuclear war and how this would impact drinking water infrastructure (Lamilla Cuellar et al., 2026). The study found that the projected increases in frost depth would likely disrupt drinking water supply across large parts of the Northern Hemisphere. While drinking water problems have been explored before in nuclear war research, this specific pathway has not. There are likely many research questions that have not been asked yet.

Besides these unknown unknowns, there is also a wide range of known unknowns, which have been highlighted in the literature (e.g. in Robock et al. (2023)) and need to be understood better:

  • There is little modern research on the ecosystem impacts of nuclear war. One study suggests that it would likely lead to a mass extinction (Kaiho, 2023).

  • Long-term Earth system impacts remain underexplored. Running large climate models is expensive, and most nuclear winter simulations therefore end after 15–20 years. However, the climate could experience long-term consequences after that.

  • Nuclear war would not occur in isolation, but would interact with other already stressed components of the Earth system, like planetary boundaries. To date, only limited exploratory research exists (Jehn, 2023).

  • A major unresolved question concerns how burnable modern cities are. Nuclear winter only happens if firestorms loft soot into the stratosphere. How much soot can be lofted depends on the amount of burnable material in the burning cities. Existing estimates span a wide range, from “nuclear winter is impossible” to “nuclear winter is guaranteed” (Hess, 2021; Wagman et al., 2020).

  • Research on the economic consequences of nuclear winter is sparse, even for basic assessments such as how much food prices might rise (e.g. Hochman et al. (2022)). As a result, how nuclear war would affect the global economy remains poorly understood.

  • There is some indication that nuclear winter research has been actively discouraged (Turchetti, 2021) and that many of the think tanks studying nuclear war have potential conflicts of interest (Egeland & Pelopidas, 2025). Understanding this in more detail would help in assessing the robustness of different research studies.

Most of the abovementioned studies are also relevant to other global catastrophes. This suggests that framing this work in an all-hazards approach (Sepasspour, 2023) would be appropriate, focusing on research which provides insights across a range of global catastrophic risks and prioritizing approaches that are effective across multiple scenarios. For example, improving models of the effects of nuclear war on climate and agriculture could also have benefits for research on other catastrophes with potential climate and food system impacts, such as major volcanic eruptions.

Key arguments from this submission for potential inclusion in the report:

  • Nuclear winter is understudied relative to its importance, largely due to funding constraints, leaving only a small number of researchers active in this field.

  • Climate impacts would be severe and rapid, but current results rely heavily on the same underlying data, making replication particularly important.

  • Food system impacts would be severe and would extend far beyond combatant countries. Large scale famine is likely if no quick adaptation happens.

  • If trade is maintained and resilient foods are employed at scale, a large fraction of famine deaths could likely be prevented.

  • The critical bottlenecks for societal response likely are cooperation, trade, inequality and coordination, not physical constraints.

  • Potential conflicts of interest in nuclear policy think tanks warrant caution in interpreting research reports.

Key research gaps that need to be addressed:

  • No model intercomparison project exists for nuclear winter. Replication using different models would strengthen the evidence base.

  • Crop models are not calibrated for nuclear winter light conditions.

  • Trade and cooperation mechanisms post-war are almost completely unexplored.

  • City flammability estimates range from “nuclear winter impossible” to “guaranteed” and need to be constrained further.

  • Resilient foods appear promising for preventing global famine, but require more research, piloting, and policy support.

  • Ecosystem impacts, long-term Earth system effects (beyond 15–20 years), economic consequences, and interactions with planetary boundaries are poorly understood.

How to cite

Jehn, F. U. (2026, February 18). Nuclear war, nuclear winter, and the food system. Existential Crunch. https://​​doi.org/​​10.59350/​​hkngk-5fq39

Recommended references and resources

Climate

  • Primary climate assessment of a major nuclear war, which underpins many subsequent studies (Coupe et al., 2019).

  • Climate assessment of smaller-scale nuclear wars (Toon et al., 2019).

  • Potential strong El Niño-like response following nuclear war would disrupt oceans and climate (Coupe et al., 2021).

  • Dependence of simulated climate effects on soot production and assumptions about burnable material, with substantial uncertainty in key inputs and the climate impacts (Wagman et al., 2020).

  • First major updated study of nuclear-winter climate since research conducted in the 1980s (Robock et al., 2007).

  • Recent review of the state of the nuclear war literature, with a focus on climate effects (National Academies of Sciences, Engineering, and Medicine, 2025).

  • Role of latent heating in enabling soot to reach the stratosphere (Tarshish & Romps, 2022).

Environmental

  • Interactions between nuclear winter and overstepped planetary boundaries (Jehn, 2023).

  • Assessment forest resources following nuclear war (Winstead & Jacobson, 2022).

Radiation

  • Disruption of public health systems in a nuclear winter (Vilhelmsson & Baum, 2023).

  • Increased ultraviolet radiation following major nuclear wars due to ozone loss (Bardeen et al., 2021).

  • Overview of radiation injuries and early fallout effects (Smith & Smith, 1981).

  • Estimation of direct nuclear war casualties (Habbick, 1983).

Global socioeconomic systems

  • Vulnerability to fuel dependency under declining trade conditions, illustrated using island nations (Boyd et al., 2023).

  • Estimated decreases in industrial output if a certain percentage of industrial production is disrupted (Blouin, Jehn, et al., 2024).

  • Disruption of food supply chains by the loss of electricity e.g. after a nuclear electromagnetic pulse (EMP) (Blouin, Herwix, et al., 2024).

  • Projected reductions in renewable energy production in a nuclear winter (Varne et al., 2024).

  • Long-term economic impacts of nuclear war on involved countries for decades (War et al., 1986).

  • Unprecedented disruption of global food trade following nuclear war (Jehn, Gajewski, et al., 2025), alongside increasing fragility in the food system over time (Puma et al., 2015).

  • Large increases in global food prices following even a small nuclear war (Hochman et al., 2022).

  • Non-combatant countries would face massive disruptions due to climate effects and disruption of the global economy (Green, 2024).

  • Several globally important ports during a nuclear winter, inferred from the identification of critical ports (Verschuur et al., 2022) would be frozen in a nuclear winter (Harrison et al., 2022) (these results are only implied, but Verschuur identifies important ports, and Harrison shows where sea ice is projected to extend to).

  • Cascading impacts in the financial system following nuclear war, with losses potentially reaching hundreds of billions of dollars (Gajewski et al., 2025).

  • Loss of access to pharmaceuticals if trade collapses following a nuclear war, illustrated using New Zealand as a case study (Wilson et al., 2025).

Agriculture

  • Overview of resilient foods and the scenarios in which they are most useful (García Martínez et al., 2025), including a research agenda for food system adaptations to nuclear winter with over 100 proposals across agriculture, technology, infrastructure, planning, and policy.

  • High likelihood of famine after nuclear war, due to dropping yields (Xia et al., 2022).

  • Potential of seaweed as an especially effective resilient food in nuclear winter (Hinge et al., 2025; Jehn et al., 2024).

  • Reduced availability of agriculture inputs (e.g. fertilizer, pesticides) following nuclear war that could reduce production by up to 70%, partly in addition to climate-caused reductions (Moersdorf et al., 2024).

  • Crops are adapted to their local climate conditions, and most would fall outside their typical climate range during nuclear winter (McLaughlin et al., 2025), with potential for crop relocation to maintain production (Blouin et al., 2025).

  • Additional yield reductions from increased ultraviolet radiation in the most severe nuclear wars (Shi et al., 2025).

  • Severe global consequences for agriculture from even regional nuclear wars (Jägermeyr et al., 2020; Özdoğan et al., 2013).

  • Potential to prevent global famine through food system adaptation and maintained trade even under severe nuclear winter conditions (Rivers et al., 2024), including through the use of non-agriculture-based foods (García Martínez et al., 2024). Evidence suggests these foods could be nutritionally adequate to prevent macro- and micronutrient deficiencies (Pham et al., 2022). However low-income countries may lack sufficient access and endure malnutrition without continued trade and significant aid (Asal et al., 2025).

  • High concentration of the food system makes it vulnerable to large-scale disruptions such as nuclear war (Clapp, 2023).

  • Estimated food supply capacity in New Zealand in a nuclear winter, using frost resistant crops (Wilson, Payne, et al., 2023).

Ecosystems

  • Potential transition of ocean systems to a new, potentially stable state following nuclear war, with unclear long-term consequences (Harrison et al., 2022).

  • Substantial increases of species extinction risk following nuclear war and the resulting nuclear winter (Kaiho, 2023).

  • Negative impacts on fisheries due to the climate changes following nuclear war, particularly in already overfished systems (Scherrer et al., 2020).

Other

  • Historical assessments of responses to nuclear winter, informed by volcanic cooling (Peregrine, 2018, 2021; Wilson, Valler, et al., 2023).

  • Potential resilience of islands to many of the effects of a nuclear winter (Boyd & Wilson, 2023).

  • Disruption of drinking water infrastructure across much of the Northern Hemisphere (Lamilla Cuellar et al., 2026), but could potentially be protected if sufficient measures are taken (Kamana-Williams et al., 2025).

  • Global Catastrophic Food Failure as a new category to better assess food system catastrophes like nuclear war (Wescombe et al., 2025).

  • Climate change will likely increase the risk of nuclear war (Egeland, 2025).

  • Prevalence of financial conflicts of interest among think tanks involved in nuclear war policy (Egeland & Pelopidas, 2025).

  • High likelihood of large-scale, long-term blackouts following nuclear war, with detailed analysis in Petermann et al. (2011); an English summary is available (original source in German): https://​​existentialcrunch.substack.com/​​p/​​the-consequences-of-blackouts

  • Limited global food storage of approximately three-quarters of a year of a year (Laio et al., 2016).

  • Overview of the global catastrophic risk space and the role of nuclear war and nuclear winter within it (Jehn, Engler, et al., 2025).

  • Overview of divergent viewpoints on soot emissions during a nuclear war (Hess, 2021).

  • A summary of the primary effects of nuclear war (Baum & Barrett, 2018).

  • Potential resilience options for disruption of fossil fuels (Nelson et al., 2024) and electricity (Williams et al., 2025).

  • A probabilistic model of uncertainty in climate and crop impacts of nuclear war and the cost-effectiveness of interventions (Denkenberger & Pearce, 2018).

References