A Review of ICAN Australia’s Groundbreaking Report
The International Campaign to Abolish Nuclear Weapons (ICAN) Australia has released a compelling briefing paper that illuminates the profound interconnections between nuclear weapons and climate change. Authored by Tilman Ruff and published in November 2024, “Nuclear Weapons and Our Climate” presents a sobering analysis of how these two existential threats amplify each other in ways that demand urgent, coordinated action.
The Nuclear Winter Scenario: More Devastating Than Previously Understood
Perhaps the most striking revelation in ICAN’s report concerns the catastrophic climate impacts of even a “limited” nuclear exchange. Drawing on peer-reviewed research published in Nature Food and other leading journals, the report demonstrates that a nuclear war involving just 2% of the global nuclear arsenal would trigger a nuclear winter scenario far more severe than many policymakers realize.
The numbers are staggering: 250 nuclear weapons of 50 kilotons each (roughly three times the Hiroshima bomb’s yield) detonated in an India-Pakistan conflict would inject 27 million tons of smoke into the stratosphere. This would plummet global temperatures by 4°C—comparable to ice age conditions—while reducing rainfall by 40% and sunlight by up to 30%. The resulting agricultural collapse would place 1.5 to 2 billion people at risk of starvation within two years.
What makes these findings particularly alarming is that they represent conservative estimates. A larger exchange between Russia and the United States involving 4,400 weapons would create temperature drops of 10°C globally and 20-35°C in parts of North America and Eurasia—essentially an extreme ice age that would doom most of humanity.
Climate Stress as a Nuclear Risk Multiplier
The report makes a compelling case that climate change itself increases nuclear risks. Drawing on World Bank data and UN assessments, ICAN documents how climate-induced water and food insecurity, displacement, and resource competition are fueling armed conflicts worldwide. The number of “internationalized intrastate” conflicts—civil wars involving external nations, often nuclear-armed ones—has steadily increased over the past decade.
This creates what the report identifies as a dangerous feedback loop: climate stress drives conflicts that increase the risk of nuclear escalation, while nuclear weapons and military spending divert resources desperately needed for climate action. The opportunity costs are substantial—global military expenditures reached a record $2.4 trillion in 2023, with nuclear weapons programs alone consuming $91.4 billion.
The Nuclear Power Proliferation Nexus
One of the report’s most provocative sections examines the “inseparable connection” between civilian nuclear power and weapons proliferation. ICAN marshals considerable evidence that nuclear power infrastructure provides the materials, expertise, and industrial capacity for weapons programs. The report cites French President Emmanuel Macron’s remarkably candid 2020 statement: “Without civil nuclear, no military nuclear, without military nuclear, no civil nuclear.”
This connection is not merely theoretical. The report documents how enrichment facilities for reactor fuel can readily produce weapons-grade uranium, while reactors inevitably create plutonium that can be extracted through reprocessing. Currently, global stockpiles of fissile materials are sufficient to build over 200,000 nuclear weapons—a sobering reminder of proliferation risks.
Ukraine: A Terrifying Preview of Nuclear Facility Vulnerabilities
The ongoing weaponization of nuclear facilities in Ukraine provides a chilling real-world demonstration of vulnerabilities the report identifies. Russia’s occupation of the Zaporizhzhia Nuclear Power Plant, attacks on power infrastructure, and the destruction of the Kakhovka Dam (which provided cooling water) have created unprecedented nuclear safety risks.
As the IAEA Director General stated in September 2024, “every single one” of the crucial pillars for ensuring nuclear safety in armed conflict has been compromised in Ukraine. This situation validates ICAN’s warning that nuclear facilities are effectively “pre-positioned radiological weapons” vulnerable to military attack, disruption of cooling systems, or loss of trained personnel.
Implications and Critical Assessment
ICAN’s report succeeds in demonstrating that nuclear weapons and climate change cannot be addressed in isolation. The interconnections are too profound—from nuclear winter’s climate impacts to climate stress increasing conflict risks, from military emissions exacerbating warming to the opportunity costs of weapons spending.
However, several aspects warrant further consideration:
- Policy Pathways: While the report strongly advocates for the Treaty on the Prohibition of Nuclear Weapons, it could benefit from more detailed analysis of interim risk reduction measures, given that nuclear-armed states remain outside the treaty framework.
- Regional Variations: The focus on India-Pakistan and US-Russia scenarios, while illustrative, leaves questions about other potential nuclear flashpoints and their specific climate impacts.
- Technological Uncertainties: Some climate modeling uncertainties remain, particularly regarding ocean system responses and regional variations in nuclear winter effects. While the report acknowledges ongoing research, these uncertainties don’t diminish the catastrophic risks identified.
- Economic Transitions: The report’s critique of nuclear power could be strengthened by more detailed analysis of renewable energy alternatives and just transition pathways for nuclear-dependent communities.
Conclusion: An Urgent Call for Integrated Action
ICAN Australia’s report makes an irrefutable case that humanity faces two paramount threats that must be addressed with equal urgency. As the report notes, “virtually every species will be harmed in a nuclear war and by global heating; only one species can stop them.”
The research presented demonstrates that preventing nuclear war could provide greater species conservation benefits than addressing deforestation, pollution, and conventional climate change combined. This startling finding underscores the absolute imperative of nuclear disarmament as part of comprehensive planetary protection.
The report emerges at a critical moment in global affairs. Recent 2024 updates from the National Security Archive reveal that the U.S. National Academies of Science, Engineering, and Medicine has established an Independent Study on Potential Environmental Effects of Nuclear War, with a final report released in July 2025. This renewed scientific attention underscores the timeliness of ICAN’s analysis.
Recent research continues to validate ICAN’s core findings. According to peer-reviewed studies, research suggests that nuclear extinction modeling by Kaiho estimates that a minor nuclear war between India and Pakistan would cause extinctions of 10-20% of species on its own, while a major U.S.-Russia exchange would cause extinctions of 40-50% of animal species—comparable to some of the “Big Five” mass extinction events in Earth’s history.
The sophistication of current climate modeling strengthens confidence in these projections. As researchers at University College London note, modern climate models are much more sophisticated than those used in the 1980s, and recent results suggest that the grim prophecy delivered by scientists 40 years ago may actually have been an underestimate.
ICAN Australia’s report represents essential reading for policymakers, climate activists, and security professionals alike. By demonstrating the inextricable links between nuclear and climate threats, it makes clear that addressing one without the other is a dangerous half-measure. The path forward requires nothing less than a fundamental reimagining of security that prioritizes human and planetary survival over military dominance.
As climate scientist Alan Robock and his colleagues have emphasized, we need nuclear disarmament so that we have “the luxury of devoting our time to solving the climate crisis.” ICAN’s report makes abundantly clear that this luxury is, in fact, a necessity for human survival.
This review was prepared independently based on ICAN Australia’s November 2024 briefing paper “Nuclear Weapons and Our Climate” by Tilman Ruff. The full report is available at icanw.org.au.
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