Resilience to Nuclear & Volcanic Winter

This is a summary. The full CEARCH report can be found here.

Key points

  • Policy advocacy, targeted at a few key countries, is the most promising way to increase resilience to global agricultural crises. Advocacy should focus on increasing the degree to which governments respond with effective food distribution measures, continued trade, and adaptations to the agricultural sector.

  • We estimate that an advocacy campaign costing ~$1million would avert 6,000 deaths in expectation. Incorporating the full mortality, morbidity and economic effects, the intervention would provide a marginal expected value of 24,000 DALYs per $100,000. This is around 30x the cost-effectiveness of a typical GiveWell-recommended charity.

  • Compared to other interventions addressing Global Catastrophic Risk (GCR), the evidence is unusually robust:

    • We know that the threat is real: volcanic cooling is confirmed by the historical and geological record.

    • We know this is neglected: current food resilience policy focuses on protecting farmers and consumers from price changes, regional agricultural shortfalls or from small global shocks. There is very little being done to prepare for a significant global agricultural shortfall.

    • We are uncertain about the effect size: we have significant uncertainty about the extent to which governments and the international community would step up to the challenge of a global agricultural shortfall. There is little evidence on the scale of the effect that a policy breakthrough would have on the human response.

  • GCR policy experts were broadly optimistic about the value of further work in this area. On average, they estimated that a two-person, five-year advocacy effort would have a 25% probability of triggering a significant policy breakthrough in one country. Experts emphasized the importance of multi-year funding to enable policy advocates to build strategic relationships. Some experts suggested that food resilience is a better framing than ASRS (cooling catastrophe) resilience for policies that protect against global agricultural shortfall.

  • We identify two main sources of downside risk. (1) Increasing resilience to nuclear winter could reduce countries’ reluctance to use nuclear weapons. (2) nuclear winter resilience efforts could be seen by other nuclear-armed states as preparation for war, thereby increasing tensions. However, these risks are unlikely to apply to broader food resilience efforts.

Executive Summary

This report addresses Abrupt Sunlight Reduction Scenarios (ASRSs) - catastrophic global cooling events triggered by large volcanic eruptions or nuclear conflicts—and interventions that may increase global resilience to such catastrophes. Cooling catastrophes can severely disrupt agricultural production worldwide, potentially leading to devastating famines. We evaluate the probability of such events, model their expected impacts under various response scenarios, and identify the most promising interventions to increase global resilience.

Volcanoes are the main source of risk according to our model, although we expect nuclear cooling events to be more damaging.

We estimate that the annual probability of an ASRS causing at least 1°C of average cooling over land is around 1 in 400, or a 20% per-century risk. Most of the threat comes from large volcanic eruptions injecting sun-blocking particles into the upper atmosphere. While the probability of a severe “nuclear winter” scenario is lower, such an event could potentially comprise a substantial portion of the expected overall burden. This is due to the compounding effects of nuclear conflict undermining the international cooperation and social stability required for an effective humanitarian response.

The annualized burden of cooling catastrophes by scenario. Much of the expected burden comes from mild and moderate cooling scenarios.

Notably, the majority of the projected burden from cooling catastrophes comes from mild and moderate events in the range of 1-4°C cooling over land. We find that in these scenarios, pragmatic policy measures and interventions could significantly decrease the risk of mass famine. Such measures include diverting animal feed towards human consumption, minimizing food waste, and facilitating efficient international agricultural trade and food aid delivery.

A hierarchy of human responses to an ASRS[1].

However, the ability to implement such measures hinges on maintaining public order, economic complexity, and international cooperation—prerequisites that may break down during more extreme cooling events as domestic food shortages increase tensions between nations. To address these risks, we identify policy advocacy aimed at raising awareness and preparedness among governments as the most promising avenue. An investment of around $1 million in advocacy efforts could plausibly catalyze major policy breakthroughs in one or more countries. Potential outcomes include government funding for research into resilient alternative food sources, comprehensive national food security risk assessments, and the development of national response plans for catastrophes that threaten global food supply.

Based on expert surveys and modeling, we estimate that such an advocacy campaign could avert the equivalent of approximately 25,000 disability-adjusted life years (DALYs) per $100,000 spent in expectation. This figure accounts for the combined mortality, morbidity, and economic impacts projected across a range of cooling scenarios and response effectiveness.

While the report acknowledges that resilient alternative food sources like mass-produced greenhouses or cellular agriculture may prove vital in worst-case scenarios, it cautions that the scaling potential of such solutions is inherently limited without broader resilience measures. On the margin we recommend expanding policy advocacy efforts as a higher-leverage approach to increase the chances of an effective, coordinated government response capable of averting mass famine during the next global cooling catastrophe. We identify a number of organizations that could perform policy advocacy in this space, including ALLFED, which specializes in post-catastrophe food resilience, and Global Shield, which is pushing for GCR policy in the US.

We emphasize that despite the uncertainties involved, investing in food system resilience through pragmatic policy advocacy represents one of the most robust strategies available for addressing the risk from global catastrophes.

Quick links to key sections of the full report

The Problem





This report was created by the Centre for Exploratory Altruism Research (CEARCH) as part of our cause-prioritization work. We also undertake research commissions.

  1. ^

    The lower stages are high-priority, as they enable conventional agriculture to continue to function. “Adaptation” includes food efficiency measures such as redirecting animal feed to humans, rationing, and reducing waste. To some extent, adaptation would be an inevitable consequence of food scarcity.