Summary/TLDR

At a Wellington lecture on February 10, 2025, Distinguished Professor Alan Robock (Rutgers University) presented compelling research on the risks of nuclear winter:

• Even 100 nuclear weapons could trigger catastrophic global cooling through urban firestorms lifting soot into the stratosphere. Despite reduced stockpiles since the Cold War, over 10,000 nuclear weapons still exist worldwide.
• Using advanced climate models, Robock's team shows that even a "limited" India-Pakistan nuclear exchange could have global impacts. A US-Russia scenario could kill 360 million directly and potentially lead to 5.3 billion deaths from global famine, with years of below-freezing temperatures in key food-producing regions.
• Recent events support the models - British Columbia and Australian wildfires (2019/20) demonstrated how smoke reaches the stratosphere, while the 1815 Tambora volcanic eruption showed how atmospheric disruption can cause global cooling and agricultural chaos.
• While fortuitously positioned geographically, NZ needs:
  
  • A national food security strategy
  • Better public education on true risks (famine vs radiation)
  • Plans for maintaining fuel and agricultural input security
  • Updated regional modelling of nuclear winter impacts
• Professor Robock advocates for complete nuclear disarmament, arguing that nuclear deterrence has evolved from "MAD" (Mutually Assured Destruction) to "SAD" (Self-Assured Destruction). 
• As a nation potentially able to maintain technological civilisation through such a crisis, New Zealand has both an opportunity and responsibility to lead in prevention and preparedness.

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Introduction

The detonation of even 100 nuclear weapons could cause urban firestorms that loft soot into the stratosphere, cooling and darkening the earth for years. The impact on global agricultural production and food trade could be catastrophic. 

On Monday 10 February two of our Islands for the Future of Humanity team attended a public lecture in Wellington by Distinguished Professor Alan Robock (Rutgers University), one of the world’s leading experts in the theory of nuclear winter. 

Professor Robock presented a career-spanning wealth of research and compelling evidence reinforcing both the urgency of nuclear disarmament and the need for better analysis of the impacts of nuclear war. 

Previously, our team has published our own analysis of New Zealand's (NZ) vulnerability and resilience to the impacts of nuclear war. We explored how our society might fare in a post-nuclear war world and how NZ could build resilience to this and other global catastrophes. Professor Robock’s career is a deep dive into the worst of these potential impacts. 

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The Enduring Threat of Nuclear Winter

While nuclear weapon stockpiles have decreased from Cold War peaks, Professor Robock's research shows that current arsenals remain sufficient to trigger catastrophic nuclear winter. More than 10,000 nuclear weapons still exist globally, with some nations like China, India and Pakistan actually increasing their arsenals. The fundamental mechanism of nuclear winter, first discovered in the 1980s, remains a grave threat: massive fires following nuclear detonations would inject smoke into the stratosphere, causing prolonged global cooling with devastating effects on agriculture.

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New Models, Same Dire Conclusions

Professor Robock's team has utilized sophisticated general circulation climate models to examine scenarios ranging from regional conflicts to full-scale nuclear war. Even a "limited" nuclear exchange between India and Pakistan (using 100-150 weapons) could have global consequences. Their 2019 model showed that beyond the immediate casualties, perhaps numbering over 27 million, the resulting climate effects would be severe and long-lasting.

A US-Russia war scenario produces even more catastrophic results. The team's models suggest that 150 Teragrams of lofted smoke would lead to:

• Initial direct fatalities of 360 million
• Potential deaths of 5.3 billion people from global famine
• Ice-age level temperature drops
• Multiple years of below-freezing temperatures, particularly in key food producing regions like Europe, China and North America

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Evidence from Natural Analogues

The models' predictions are supported by real-world examples. Recent events like the British Columbia and Australian wildfires (2019/20) have demonstrated how smoke can be lofted into the stratosphere. The Tambora volcanic eruption of 1815 provides historical evidence of how sudden atmospheric disruptions can trigger global cooling and agricultural turmoil in the ‘year without a summer’.

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Implications for New Zealand

These findings have relevance for New Zealand's resilience planning. In an ideal world nuclear weapons would be banned, but until such time non-combatant nations like NZ need to consider protecting themselves. While our previous analysis highlighted trade disruption and energy security as key vulnerabilities, Robock's research implies some important considerations:

• NZ needs a national food security strategy and plan as the agricultural impact could be severe, with reduced yields and rainfall affecting even Southern Hemisphere nations.
• There is a need for public education, due to the persistent misconception (illustrated again during question time at the lecture) that radiation risks are the main concern in nuclear war. Yet it is the potential famine that could kill ten times as many people as the direct impacts of blasts. 
• NZ needs to consider how to maintain security in liquid fuels and industrial agricultural inputs. As Professor Robock asserted ‘yes’ there is a risk of societal collapse if trade in these commodities is interrupted for an extended period. 

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A Call to Action

Professor Robock's message is clear: "get rid of the weapons." His team is developing software to help nuclear-armed nations better understand the consequences of nuclear war, supporting the argument that nuclear deterrence has evolved into what he calls "SAD" (Self-Assured Destruction – a suicide bomber strategy) rather than "MAD" (Mutually Assured Destruction).

This research adds urgency to our previous recommendations for New Zealand:

• The need to update the NZ Planning Council’s 1987 study on the impacts of nuclear war with modern modelling
• The importance of developing robust food production and distribution plans
• The critical role of clear public communication about actual risks
• The value of strengthening regional relationships and trade networks

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Moving Forward

Professor Robock has made a career as not merely a climate scientist, but also an activist campaigning to reduce the risk of nuclear war. He has a strong message for scientists, you cannot just conduct research, you must advocate for the implications, and campaign for change when you uncover risk. 

As Carl Sagan noted, nuclear disarmament is a matter of "elementary planetary hygiene." While New Zealand continues to advocate for global nuclear disarmament, including through a current UN initiative to conduct a scientific study of the impacts of nuclear war, we must also enhance our resilience to potential nuclear winter scenarios.

The totality of Professor Robock’s research reinforces that nuclear winter remains a critical global catastrophic risk requiring both prevention and preparedness. As one of the nations best positioned to maintain technological civilisation through such a crisis, New Zealand has both an opportunity and an obligation to lead in this area.

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You can watch Alan Robock’s 2022 TED talk below.

This blog builds on our previous work examining New Zealand's vulnerability and resilience to the impacts of nuclear war. For background, see our Main Report “Aotearoa NZ, Global Catastrophe, and Resilience Options"

You can join us for a free webinar on Catastrophic Electricity Loss (as might be caused by a nuclear EMP) on 26 February 2025, register here.

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