Nuclear Conflict
1. Scientific definition
Nuclear Conflict refers to the use, threatened use, escalation, or systemic destabilization associated with nuclear weapons. It includes direct blast, heat, radiation, infrastructure destruction, political escalation, command and control failure, arms-racing dynamics, nuclear winter scenarios, and long-lasting damage to food systems and institutional capacity. Robock et al. model how even partial use of current nuclear arsenals could produce severe global climatic cooling and agricultural collapse, giving the threat a scale that extends beyond the battlefield (Robock et al., 2007).
The term should not be confused with every geopolitical dispute involving a nuclear-armed state. Many crises remain below the nuclear threshold. The systemic danger arises when deterrence, escalation control, military signaling, technological warning systems, arms-control regimes, and political judgment interact under conditions of stress. SIPRI describes nuclear risks as intertwined with great-power competition, regional conflicts, cyber operations, and emerging technologies, which places nuclear danger inside a wider network of strategic instability (SIPRI, 2025).
Nuclear Conflict also differs from conventional war because the upper range of damage is qualitatively different. Scouras classifies large nuclear war as a global catastrophic risk, with potential to kill billions and set civilization back centuries. That assessment supports a very high systemic interpretation without implying certainty about human extinction or any fixed pathway from crisis to collapse (Scouras, 2019).
A numerical threshold in the Apocalypse Clock model should not be read as an empirical nuclear tipping point, a physical boundary, or a deterministic forecast. Nuclear escalation depends on human decisions, technical systems, doctrine, warning procedures, alliance structures, and crisis dynamics. The threshold functions as a normalized systemic-risk anchor, informed by the catastrophic potential of large nuclear war and by the fact that deterrence and command structures still create barriers, however imperfect (Scouras, 2019; SIPRI, 2025).
2. Empirical evidence base
The scale evidence is anchored in nuclear winter modeling and global catastrophic risk analysis. Robock et al. show that even a partial use of current nuclear arsenals could generate severe global climatic cooling and agricultural collapse. Scouras's assessment places large nuclear war among global catastrophic risks, with possible consequences measured in billions of deaths and civilizational regression over centuries. These sources justify a near-maximal scale interpretation, with residual uncertainty about the outer boundary of harm (Robock et al., 2007; Scouras, 2019).
Urgency comes from contemporary nuclear-risk assessments. The Bulletin of the Atomic Scientists set the Doomsday Clock to 89 seconds to midnight in 2025 and moved it to 85 seconds in January 2026, explicitly citing worsening nuclear dangers, eroding arms control, and active conflicts. This is institutional warning language rather than a probabilistic forecast, yet it supports the judgment that nuclear escalation risk is already acute (Bulletin of the Atomic Scientists, 2025; Bulletin of the Atomic Scientists, 2026).
SIPRI's latest evidence gives the acceleration dimension a concrete empirical base. At the start of 2026, the nine nuclear-armed states held about 12,187 warheads, with 9,745 in military stockpiles and around 4,012 deployed (SIPRI, 2026). SIPRI also reports that nearly all nuclear-armed states are modernizing, and in some cases expanding, their arsenals, with military stockpiles beginning to increase again after decades of decline. The acceleration signal is therefore serious, though total inventories remain below Cold War peaks (SIPRI, 2025).
The interdependence evidence is strategic rather than ecological or economic. SIPRI describes nuclear risk as connected to great-power competition, regional conflicts, cyber operations, and emerging technologies. Doomsday Clock statements also link nuclear danger with climate, biological, and AI threats. These connections do not make nuclear weapons the cause of every global risk, but they show how nuclear escalation could be affected by several other destabilizing pressures (SIPRI, 2025; Bulletin of the Atomic Scientists, 2025).
Irreversibility is supported by climate-model studies and catastrophic-risk assessment. Nuclear winter scenarios involve smoke-driven global cooling lasting multiple years, with agricultural collapse as a major pathway of harm. Scouras adds that large nuclear war could cause long-lasting damage to infrastructure, economies, and human capital. Some ecosystems and societies might eventually recover over decades, but the damage would not resemble a short emergency followed by ordinary reconstruction (Robock et al., 2007; Scouras, 2019).
Governance failure is visible in arms-control erosion and modernization. SIPRI documents the weakening or collapse of key arms-control agreements, including the expiry of New START in February 2026 without a replacement, and large-scale modernization programs across all nuclear-armed states. The Bulletin's 2025 statement says national leaders and their societies have failed to do what is needed to change course on nuclear and other global risks. Existing instruments such as the NPT and some bilateral arrangements still matter, yet the evidence indicates severe strain in the governance architecture intended to contain nuclear danger (SIPRI, 2025; SIPRI, 2026; Bulletin of the Atomic Scientists, 2025).
Growth-rate evidence is proxy-based, not a direct measurement of annual collapse hazard. SIPRI and FAS indicate that total inventories are roughly stable around 12,000 warheads, but usable military stockpiles are beginning to increase again and modernization is accelerating. The Apocalypse Clock model translates these trends into a calibrated systemic risk-growth proxy. That proxy reflects stockpile modernization pressure and crisis uncertainty rather than a direct empirical time series of nuclear-war probability (SIPRI, 2025; FAS, 2026).
3. Mechanism of systemic destabilization
Nuclear Conflict destabilizes systems through a rare combination of speed, scale, and coupling. A crisis can unfold faster than deliberative institutions can respond, and the consequences can propagate from immediate destruction into climate, agriculture, public health, economic systems, and political order. Robock et al. provide the physical pathway by modeling how nuclear detonations could inject smoke into the atmosphere and produce severe global cooling with agricultural consequences (Robock et al., 2007).
The first mechanism is escalation under uncertainty. Nuclear command systems operate in conditions where incomplete information, compressed decision time, cyber vulnerability, regional war, and great-power rivalry can interact. SIPRI’s 2025 assessment links nuclear risk to great-power competition, regional conflicts, cyber operations, and emerging technologies. The systemic danger arises because each domain can degrade the reliability of the others during a crisis (SIPRI, 2025).
The second mechanism is arsenal modernization. Modernization does not automatically produce war, and total inventories remain below Cold War peaks. The problem lies in renewed military stockpile growth, deployment patterns, and technological upgrading across nearly all nuclear-armed states. SIPRI's 2026 figures show a world with about 12,187 warheads and modernization in all nine nuclear-armed states, creating a background of elevated strategic pressure (SIPRI, 2026).
The third mechanism is governance erosion. Arms-control agreements reduce uncertainty, constrain worst-case planning, and create channels of verification. SIPRI documents weakening or collapse of key arms-control arrangements, and the Bulletin identifies political leadership failure as part of the contemporary risk environment. Once governance mechanisms erode, deterrence becomes more dependent on trust, technical reliability, and crisis judgment precisely when strategic suspicion is increasing (SIPRI, 2025; Bulletin of the Atomic Scientists, 2025).
The fourth mechanism is climatic amplification after use. Nuclear war would not remain a military event if smoke-driven cooling damaged global agriculture. Robock et al. model severe global climatic cooling and agricultural collapse after partial arsenal use. The pathway is systemic because the harm is transmitted through atmosphere, sunlight, growing seasons, food availability, and social stability, rather than remaining confined to the original target zones (Robock et al., 2007).
The fifth mechanism is long institutional damage. Scouras's analysis emphasizes that large nuclear war could kill billions and set civilization back centuries. That framing points to more than immediate mortality. Infrastructure, economies, governance capacity, technical knowledge, health systems, and human capital could all be damaged at the same time. A society can sometimes rebuild after localized destruction; synchronized degradation across several foundational systems creates a different recovery problem (Scouras, 2019).
The sixth mechanism is cross-domain interdependence. SIPRI identifies links between nuclear danger, regional conflicts, cyber operations, emerging technologies, and great-power competition. Doomsday Clock statements connect nuclear danger with other systemic risks such as climate, biological threats, and AI. These links do not imply a single deterministic cascade, but they show how nuclear risk can become more volatile when other systems are also stressed (SIPRI, 2025; Bulletin of the Atomic Scientists, 2025).
The seventh mechanism is asymmetry between prevention and consequence. Nuclear Conflict is a low-frequency event relative to many chronic risks, yet its upper damage range is extreme. That asymmetry gives governance unusual ethical weight: success is often invisible, failure can be civilizational. The Apocalypse Clock model therefore treats normalized nuclear scores as systemic-risk inputs rather than direct empirical measurements, with Scouras's global catastrophic risk framing serving as an anchor for the high destabilization level (Scouras, 2019).
The eighth mechanism is partial irreversibility. Nuclear winter effects, infrastructure loss, institutional breakdown, and human capital destruction would not necessarily be permanent in every domain, but recovery could take decades or centuries depending on the scale of use. Robock et al. support the multi-year climatic and agricultural pathway, and Scouras supports the long-duration civilizational damage pathway. Nuclear Conflict therefore belongs among systemic threats whose main danger is not frequent occurrence, but extreme consequence under failure (Robock et al., 2007; Scouras, 2019).
4. Sources used
Robock et al., 2007: Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences, Journal of Geophysical Research, 112, D13107.
URL: https://climate.envsci.rutgers.edu/pdf/RobockNW2006JD008235.pdf
Supports: Climate-model evidence that even partial nuclear arsenal use could produce severe global cooling and agricultural collapse.
Scouras, 2019: Nuclear War as a Global Catastrophic Risk, Journal of Benefit-Cost Analysis.
URL: https://www.jhuapl.edu/sites/default/files/2022-12/NuclearWarGlobalRisk.pdf
Supports: The interpretation of large nuclear war as a global catastrophic risk with potential for billions of deaths and long-duration civilizational damage.
Bulletin of the Atomic Scientists, 2025: 2025 Doomsday Clock Statement, Bulletin of the Atomic Scientists.
URL: https://thebulletin.org/wp-content/uploads/2025/01/2025-Doomsday-Clock-Statement.pdf
Supports: Urgency evidence on the 89-second setting, collapsing arms control, the wars in Ukraine and the Middle East, links to climate, biological and AI risks, and the failure of leaders to change course.
Bulletin of the Atomic Scientists, 2026: It is 85 seconds to midnight (press release, 27 January 2026), Bulletin of the Atomic Scientists.
URL: https://thebulletin.org/2026/01/press-release-it-is-85-seconds-to-midnight/
Supports: The 2026 move of the Doomsday Clock to 85 seconds to midnight, citing expanding arsenals and collapsing global understandings.
SIPRI, 2025: SIPRI Yearbook 2025: Armaments, Disarmament and International Security, Summary.
URL: https://www.sipri.org/sites/default/files/2025-06/yb25_summary_en.pdf
Supports: Evidence on global nuclear warhead numbers, military stockpiles, deployed warheads, modernization, and renewed stockpile growth.
SIPRI, 2025: SIPRI Yearbook 2025, International stability, human security and the nuclear challenge.
URL: https://www.sipri.org/sites/default/files/SIPRIYB25c01.pdf
Supports: Evidence on the coupling of nuclear risks with great-power competition, regional conflicts, cyber operations, and emerging technologies.
SIPRI, 2025: SIPRI Yearbook 2025, Chapter 6: World nuclear forces (Kristensen and Korda).
URL: https://www.sipri.org/sites/default/files/SIPRIYB25c06.pdf
Supports: Evidence on arms-control weakening, modernization programs, and governance strain among nuclear-armed states.
FAS, 2026: Status of World Nuclear Forces.
URL: https://fas.org/initiative/status-world-nuclear-forces/
Supports: Proxy-based evidence on nuclear inventories, usable stockpiles, modernization pressure, and systemic risk-growth interpretation.
SIPRI, 2026: SIPRI Yearbook 2026, Chapter 8: World nuclear forces (Kristensen and Korda).
URL: https://www.sipri.org/sites/default/files/YB26%2008%20World%20Nuclear%20Forces.pdf
Supports: January 2026 estimates of about 12,187 total warheads, 9,745 in military stockpiles and 4,012 deployed; modernization by all nine states; expiry of New START in February 2026 without replacement.