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COMMITTEE ON INDEPENDENT STUDY ON POTENTIAL ENVIRONMENTAL EFFECTS OF NUCLEAR WAR¹

ANTONIO J. BUSALACCHI, JR. (NAE), Co-Chair, University Corporation for Atmospheric Research

MENG-DAWN CHENG, Co-Chair, Oak Ridge National Laboratory

WILLIAM D. COLLINS, Lawrence Berkeley National Laboratory and the University of California, Berkeley

MICHAEL S. ELLIOTT, Senior Executive Service (retired)

JASON H. KNOUFT, Saint Louis University and the National Great Rivers Research and Education Center

MAUREEN LICHTVELD (NAM), University of Pittsburgh

NICOLE S. LOVENDUSKI, University of Colorado Boulder

KATHERINE A. LUNDQUIST, Lawrence Livermore National Laboratory

JAMES T. RANDERSON (NAS), University of California, Irvine

OSVALDO E. SALA, Arizona State University

SUSAN SOLOMON (NAS), Massachusetts Institute of Technology

WILLIAM J. TEDESCHI, MITRE Corporation

ROBERTO O. VALDIVIA, Oregon State University

CHRISTINE WIEDINMYER, University of Colorado Boulder

AIXI ZHOU, Norfolk State University

Study Staff

LIANA VACCARI, Study Director, Board on Chemical Sciences and Technology (BCST)

LESLIE BEAUCHAMP, Senior Program Assistant, Board on Environmental Studies and Toxicology and Nuclear and Radiation Studies Board (NRSB) (until October 2024)

APURVA DAVE, Senior Program Officer, Board on Atmospheric Sciences and Climate (BASC)

CHARLES D. FERGUSON, Senior Board Director, NRSB and BCST

DARLENE GROS, Senior Program Assistant, NRSB

NANCY HUDDLESTON, Director, Communications and Media, Division on Earth and Life Studies

KATRINA HUI, Associate Program Officer, BASC

MICHAEL T. JANICKE, Senior Program Officer, NRSB

MICAH LOWENTHAL, Senior Board Director, Committee on International Security and Arms Control

DANIEL MULROW, Program Officer, NRSB

AMANDA STAUDT, Senior Board Director, BASC (until July 2023)

KASEY WHITE, Board Director, BASC

KAYANNA WYMBS, Research Assistant, BCST

NUCLEAR AND RADIATION STUDIES BOARD

WILLIAM H. TOBEY, Chair, Los Alamos National Laboratory

AMY J. BERRINGTON DE GONZÁLEZ, Vice Chair, Institute of Cancer Research

SALLY A. AMUNDSON, Columbia University Medical Center

BROOKE R. BUDDEMEIER, Lawrence Livermore National Laboratory

MADELYN R. CREEDON, Green Marble Group, LLC

LAWRENCE T. DAUER, Memorial Sloan Kettering Cancer Center

SHAHEEN A. DEWJI, Georgia Institute of Technology

PAUL T. DICKMAN, Argonne National Laboratory (retired)

DONALD P. FRUSH, Duke University Medical Center

ALLISON M. MACFARLANE, University of British Columbia

ELEANOR MELAMED, National Nuclear Security Administration (retired)

PER F. PETERSON (NAE), University of California, Berkeley

R. JULIAN PRESTON, Environmental Protection Agency (Special Government Employee)

MONICA C. REGALBUTO, Idaho National Laboratory

Board Staff

CHARLES D. FERGUSON, Senior Board Director

MICHAEL T. JANICKE, Senior Program Officer

DANIEL MULROW, Program Officer

DARLENE GROS, Senior Program Assistant

LESLIE BEAUCHAMP, Senior Program Assistant (until October 2024)

LAURA D. LLANOS, Finance Business Partner

COMMITTEE ON INTERNATIONAL SECURITY AND ARMS CONTROL

PERSIS S. DRELL (NAS), Chair, Stanford University

RAYMOND JEANLOZ (NAS), Chair, University of California, Berkeley (until December 2024, member since January 2025)

ROSE E. GOTTEMOELLER, Vice Chair, Stanford University

ANDREW G. ALLEYNE (NAE), University of Minnesota

KRISTIE A. BOERING (NAS), University of California, Berkeley (since January 2025)

MARIANA BUDJERYN, Harvard University

MATTHEW G. BUNN, Harvard University

NANCY D. CONNELL, Johns Hopkins Center for Health Security

LINDA T. ELKINS-TANTON (NAS), Arizona State University

STEVEN A. FETTER, University of Maryland

DIANE E. GRIFFIN, Johns Hopkins University Bloomberg School of Public Health¹

MARGARET A. HAMBURG (NAM), Nuclear Threat Institute

JOHN INGLIS, Cold Spring Harbor Laboratory

MORIBA K. JAH, University of Texas at Austin

ALASTAIR IAIN JOHNSTON, Harvard University (until December 2024)

JAMES W. LEDUC, The University of Texas Medical Branch at Galveston

JEFFREY LEWIS, Middlebury Institute of International Studies

HERBERT S. LIN, Stanford University

DOUGLAS L. LOVERRO, Loverro Consulting, LLC

STUART J. RUSSELL, University of California, Berkeley (since January 2025)

LORA LANNAN SAALMAN, Stockholm International Peace Research Institute

VICTORIA A. SAMSON, Secure World Foundation

RACHEL A. SEGALMAN (NAE), University of California, Santa Barbara

JIM TIMBIE, Stanford University

JOHN G. HILDEBRAND (NAS), Ex Officio Member, University of Arizona, Tucson

Project Staff

MICAH LOWENTHAL, Senior Board Director

NANCY CONNELL, Scholar (Intermittent)

RITA GUENTHER, Senior Program Officer

ALEX TEMPLE, Program Officer

CARMEN SHAW, Associate Program Officer

CANDACE HUNTINGTON, Research Associate (Intermittent)

MARGARET MCCARTHY, Research Associate

HOPE HARE, Administrative Assistant

BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE

BRAD R. COLMAN, Chair, Bayer/The Climate Corporation (retired) (Chair since October 2024, and member until September 2024)

MARY GLACKIN, Chair, The Weather Company, an IBM Business (retired) (until September 2024)

JOSEPH ÁRVAI, University of Southern California

CYNTHIA S. ATHERTON, Heising-Simons Foundation (formerly)

ELIZABETH A. BARNES, Colorado State University

BART E. CROES, California Air Resources Board (retired)

MINGHUI DIAO, San Jose State University

NEIL DONAHUE, Carnegie Mellon University

LESLEY-ANN DUPIGNY-GIROUX, University of Vermont

EFI FOUFOULA-GEORGIOU (NAE), University of California, Irvine

KEVIN GURNEY, Northern Arizona University

MARIA CARMEN LEMOS (NAS), University of Michigan

ANDREA LOPEZ LANG, University of Wisconsin–Madison

ZHANQING LI, University of Maryland

AMY MCGOVERN, University of Oklahoma

LINDA O. MEARNS, National Center for Atmospheric Research¹

JONATHAN A. PATZ (NAM), University of Wisconsin–Madison

BERNADETTE WOODS PLACKY, Climate Central

KEVIN REED, Stony Brook University

JAMES MARSHALL SHEPHERD (NAS/NAE), University of Georgia (until September 2024)

ARADHNA TRIPATI, University of California, Los Angeles

Board Staff

KASEY WHITE, Board Director

APURVA DAVE, Senior Program Officer

APRIL MELVIN, Senior Program Officer

STEVEN STICHTER, Senior Program Officer

MORGAN DISBROW-MONZ, Program Officer

KATRINA HUI, Associate Program Officer

KATELYN CREWS, Senior Program Assistant

ANNE MANVILLE, Senior Program Assistant

LINDSAY MOLLER, Senior Program Assistant

Reviewers

This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.

We thank the following individuals for their review of this report:

Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release. The review of this report was overseen by KOZO SAITO, University of Kentucky (retired), Affiliation of Coordinator, and SUSAN BRANTLEY (NAS), The Pennsylvania State University. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.

Acknowledgments

The committee would like to give a special thanks to colleagues who supported this challenging and multifaceted project focused on reviewing current modeling related to the potential environmental effects of nuclear war that are potentially regional to global and across different earth systems. In particular Lois Buitano and Mark Suriano (National Nuclear Security Administration) were key to the success of this study. The National Nuclear Security Administration, MITRE and the staff at the Beckman Center in Irvine, CA also assisted in supporting off-site meetings for the committee.

Many individuals, organizations, universities and U.S. government agencies contributed to the completion of this report. The committee and National Academies’ staff appreciate their kind assistance. Presenters for the numerous briefings are listed in appendix A. Volunteering their time to give valuable insight was crucial to the information gathered and compiled in this report. These individuals include:

Preface

War is devastating to society; nuclear war even more so. Since the beginning of civilization, humankind has been at war with itself, but no weapon has ever come close to the formidable power of a nuclear weapon. A nuclear war would not only brutally take human lives and leave everlasting wounds on society, but also cause significant and sometimes irreversible damage to the environment.

The thermal, radiological, and blast effects of a nuclear detonation could severely impact the environment and destroy life. A modern city could become ruins in minutes, leaving behind rubble and fires ignited by ruptured gas lines, collapse of power grids and electrical shortages. The air could become so radiologically contaminated and heavily polluted in minutes to months, the water undrinkable, and the soil of the impacted area uninhabitable and unsuitable for agricultural use for decades to come. Fires from large nuclear detonations could potentially alter life on Earth to a degree never seen before in human history if a large quantity of smoke is produced. Fire-produced smoke could be injected into the stratosphere, then circulate around the globe for years blanketing the planet, shielding the sunlight and cooling the planet surface, thereby disrupting the food chain and production ecosystem.

Nuclear weapons have been used twice in the history of humankind, on two large cities in Japan, Hiroshima and Nagasaki, during World War II. Impacts to Japan and Japanese were cataclysmic. From this military execution humankind saw the inconceivable power and horror of nuclear weapons for the first time. In the late 1970s and early 1980s, the Cold War escalated between the United States and the Soviet Union, prompting large stockpiles of nuclear weapons in both countries.

Fear of nuclear war led to studies of potential consequences such as “nuclear winter,” a term that was coined by scientists studying potential environmental effects that may arise from nuclear detonations. Radiological effects on human species caused by radiation and the fallout of toxic metals and radioactive particulate materials are horrendous, and as such, have been investigated extensively. A large volume of the data to the radiological effects are available in the open literature and are beyond the statement of task for of this report. However, the impacts on the ecosystem (air, water, soil, cryosphere, and biosphere) and its services (built environment, medical, food, transportation, finance/commerce, and so on) have not been quantified in the past.

Eighty years later from the first use of two kiloton-scale nuclear fission weapons and 40 years after the warning of nuclear winter, is humankind less vulnerable today from the threat of nuclear war?

Contents

SUMMARY

1 INTRODUCTION

1.1 Background and Study Motivation

1.2 Study Scope and Approach

1.3 Previous Work on Environmental Effects of Nuclear War

1.4 Organization of this Report

1.5 References

2 EMPLOYMENT SCENARIOS AND WEAPONS EFFECTS

2.1 Introduction

2.2 Employment Scenarios

2.3 Weapon Effects and Energy Distribution

2.4 Summary

2.5 Findings and Recommendations

2.6 References

3 FIRE DYNAMICS AND EMISSIONS

3.1 Introduction

3.2 Fuel Characteristics and Loading

3.3 Ignition, Spread, Burn Area, and Fuel Consumption

3.4 Emission Factors

3.5 Summary

3.6 Findings and Recommendations

3.7 References

4 PLUME RISE, FATE AND TRANSPORT OF AEROSOLS, AND GAS-PHASE CHEMISTRY

4.1 Introduction

4.2 Plume Dynamics and Transport Modeling

4.3 Tropospheric Behavior and Impacts

4.4 Stratospheric Behavior and Impacts

4.5 Summary

4.6 Findings and Recommendations

4.7 References

5 PHYSICAL EARTH SYSTEM IMPACTS

5.1 Introduction

5.2 Solar Radiation

5.3 Stratospheric Ozone

5.4 Temperature

5.5 Hydrologic Cycle

5.6 Ocean Physical Properties and Circulation

5.7 Cryosphere

5.8 Summary

5.9 Findings and Recommendations

5.10 References

6 ECOSYSTEM IMPACTS

6.1 Introduction

6.2 Drivers of Ecosystem Functioning Under Nuclear War Induced Environmental Change

6.3 Impacts on Ecosystem Structure and Functioning

6.4 Biodiversity Change

6.5 Key Uncertainties and Data Gaps

6.6 Summary

6.7 Findings and Recommendations

6.8 References

7 SOCIETAL AND ECONOMIC IMPACTS

7.1 Introduction

7.2 Impacts on Ecosystem Services

7.3 Impacts on Human Health

7.4 Impacts on Society

7.5 Summary

7.6 Findings and Recommendations

7.7 References

8 CONCLUSION

8.1 Overarching Considerations

8.2 Employment Scenarios and Weapons Effects

8.3 Fire Dynamics and Emissions

8.4 Plume Rise, Fate and Transport of Aerosols, and Gas-Phase Chemistry

8.5 Physical Earth System Impacts

8.6 Ecosystem Impacts

8.7 Societal and Economic Impacts

8.8 References

APPENDIX A: PUBLIC MEETING AGENDAS

APPENDIX B: COMMITTEE BIOSKETCHES

BOXES, FIGURES, AND TABLES

BOXES

1-1 Historical Nuclear Bombings

1-2 Statement of Task

1-3 Crosscutting Terms

1-4 Causal Pathway

2-1 Key Terms

2-2 Perspective on the use of The Effects of Nuclear Weapons by Glasstone and Dolan in this study

2-3 Radioactive aerosol formation resulting from a nuclear detonation

3-1 Key Terms

4-1 Key Terms

4-2 The 2019–2020 Australian Wildfire Event as a Test Case for the Efficiency of Stratospheric Aerosol Injection

4-3 Solar Geoengineering

5-1 Key Terms

6-1 Key Terms

6-2 Case Study: Terrestrial Impacts from Mt. Pinatubo

6-3 Case Study: Terrestrial Impacts from Krakatoa

6-4 Case Study: Fresh Water Impacts from Mt. St. Helens

7-1 Key Terms

7-2 Globalization: How Shocks May Affect an Interconnected World

7-3 Impacts on Ecosystem Services

7-4 Impacts on Human Health

7-5 Impacts on Societal Resilience

FIGURES

S-1 Causal pathway of possible physical Earth system, ecosystem, societal, and economic impacts as an outcome of the detonation of a nuclear weapon

S-2 Stratospheric aerosol—observations, processes, and impact on climate

S-3 Causal sequence of dominant interactions between the components of the physical Earth system in response to the forcing due to the smoke and other pollutants resulting from a nuclear exchange

S-4 Conceptual diagram of the environmental effects of a nuclear war on terrestrial and marine ecosystems, through changes in temperature, precipitation, and solar radiation

S-5 Interactions and interdependencies among human and natural systems

1-1 Causal pathway of possible physical Earth system, ecosystem, societal, and economic impacts as an outcome of the detonation of a nuclear weapon

2-1 Historical U.S. Nuclear Weapons Stockpile

2-2 Estimated Nuclear Stockpiles for 1950 to ca. 2023

2-3 Nuclear cloud after detonations in Hiroshima and Nagasaki

2-4 An illustrative bimodal distribution of radioactive aerosol particles produced by a nuclear detonation

2-5 Slant range for airbursts at a range of yields at specified radiant exposure levels for visibility of 12 miles

2-6 Areas of blast, thermal, and prompt radiation effects for surface detonations 0.1-, 1-, 10-, and 100-kt weapon yields

2-7 Surface incident energy for a 10-kt detonation in San Francisco

3-1 Comparisons of fuel mass density per capita (Mf) for all districts in Washington, DC and the value from an earlier study

3-2 Blast damage zones, including observable features for a 10-kt detonation

4-1 Stratospheric aerosol—Observations, processes, and impact on climate

4-2 Fire plume after the atomic bomb detonation in Hiroshima on August 6, 1945

4-3 Vertical profiles of horizontally integrated smoke mass from Weather Research and Forecasting plume-rise simulations showing sensitivity to atmospheric moisture, wind speed, and fuel loading

4-4 Scanning electron microscope images of soot aggregates in wildfire plumes

4-5 Strontium-90 observed in the stratosphere and on the surface from 1950s to 1970s

4-6 Wet scavenging process for black carbon

5-1 Causal sequence of interactions between the components of the physical Earth system in response to the forcing due to the smoke and other pollutants resulting from a nuclear exchange

5-2 Response of downwelling surface shortwave radiation to stratospheric black carbon aerosol load

5-3 Response of downwelling surface shortwave radiation to stratospheric aerosol load

5-4 Global annual mean maximum cooling and drying responses to changes in downwelling surface shortwave radiation derived from nuclear war climate model simulations

5-5 Global annual mean surface air temperature and precipitation responses to stratospheric aerosol mass

6-1 Conceptual diagram of the climate effects of a nuclear war on terrestrial and marine ecosystems, through changes in temperature, precipitation, and solar radiation

6-2 Conceptual diagram of the environmental effects of a nuclear war on terrestrial net primary production (NPP)

6-3 Observations of aboveground net primary production (ANPP) in the Great Plains of North America along a temperature gradient showed a significant decrease in ANPP with increasing temperature

6-4 Direct and indirect effects of reduction of temperature due to nuclear war and its duration on biodiversity

7-1 Interactions and interdependencies among human and natural systems

7-2 Globalization over the years

7-3 World Food Price Index over the years (1961-2024) and selected major global events that impacted global food prices

7-4 Wheat and rice trade networks, showing the largest export links that together account for 80% of the total trade for each network

7-5 Food systems are complex and extend from local to global scales

7-6 The multidimensional nature and interconnectedness of community resilience capitals are the foundation for measurement efforts from local to global scales

7-7 Five pillars supporting a bridge to build resilience

8-1 Causal pathway of possible physical Earth system, ecosystem, societal, and economic impacts as an outcome of the detonation of a nuclear weapon

TABLES

S-1 Environmental Effects of Nuclear War Model Intercomparison Project

2-1 Current Estimated Stockpiles

2-2 Proposed Plausible Scenarios for Nuclear Detonations with Large-, Moderate-, Regional-, and Limited-Scale Exchanges

2-3 Example Fallout-Free Height of Burst Values for Weapon Yields in the Employment Scenarios

2-4 Optimal Height of Burst to Maximize the Area of Blast Overpressure of 140 kPa and Distance from Ground Zero Where the Overpressure Is Expected

2-5 Duration of Thermal Pulse

2-6 Example Calculated Values of Ground Range and Ground Area

3-1 Building Structure and Content Fuel Loads in U.S. Urban Areas

3-2 Effective Fire Load Density Values for Some Land-Use Categories in the United States

3-3 Fire Load Density Data in Countries and Regions Other than the United States

3-4 Summarized Fuel Loadings and Combustion Completeness in Wildland Fires

3-5 Sampling of Suggested Mass-Based Fuel Loadings from Various Literature Sources with a Focus on Urban Fuel

3-6 Temperature as a Measure of the Degree of Molecular Activity of a Material Compared to a Reference Point

3-7 Examples of Heat Flux Rates of Heat Energy Transferred per Surface Unit Area

3-8 Damage Approximations at Specific Overpressure Values

3-9 Combustion Completeness Assumptions for Studies Focusing on Urban Scenarios

3-10 Emission Factors for Key Gas-Phase and Aerosol Species Emitted from Various Types of Biomass Burning

3-11 Emission Factors from Urban Fuels

4-1 Settling Velocity (V_ts), Relaxation Time (RT), and Distance (D) That Aerosols of Varying Diameter (D_p) Fall in 24 Hours in Calm Air at Standard Temperature and Pressure Conditions

7-1 Estimated Production Losses of Major Crop Systems by Regions as a Consequence of a Limited Regional-Scale Nuclear Exchange

8-1 Environmental Effects of Nuclear War Model Intercomparison Project

Acronyms and Abbreviations

Glossary

Aerosol (Chapters 1 and 4): Any solid or liquid droplets suspended in the atmosphere.

Aerosol Single-Scattering Albedo (SSA) (Chapter 5): Ratio of scattering efficiency to total extinction efficiency of a particle. A lower aerosol SSA means more light-absorbing material (e.g., black carbon), whereas a higher aerosol SSA means a more light-scattering particle.

Albedo (Chapter 5): Reflectivity of Earth’s surface, measured as a fraction. An albedo of zero means all incident sunlight is absorbed, and an albedo of 1 means all incident sunlight is reflected.

Albedo Feedback (Chapter 5): Positive feedback in which a temperature-induced change in the area of highly reflective snow cover, glaciers, land ice, and/or sea ice alters Earth’s albedo and hence amplifies the change in Earth’s surface temperature.

Aquaculture (Chapter 7): Farming of aquatic organisms such as fish, crustaceans, mollusks, and aquatic plants, involving their cultivation in natural or controlled marine or freshwater environments.

Ash (Chapter 5): S particulate remnants resulting from fire, either temporarily persisting in the atmosphere or immediately deposited on the landscape.

Backscattering Fraction (Chapter 5): Fraction of sunlight scattered backward (in the direction of incidence) when sunlight scatters off an aerosol or cloud droplet. Larger backscattering fractions reduce the amount of sunlight transmitted to Earth’s surface.

Biomass (Chapter 6): Total mass of living organisms within a given area of an ecosystem. It can be measured for different trophic levels (e.g., producer biomass, consumer biomass) or for the entire ecosystem.

Biodiversity (Chapter 6): Variety of life forms, including plants, animals, and microorganisms, that exist in a particular ecosystem, biome, or on the entire planet. It encompasses diversity at the genetic, species, and community levels.

Biome (Chapter 6): Major regional or global community of plants and animals with similar life forms and environmental conditions.

Climate–carbon cycle (Chapter 7): Interconnected processes and feedbacks between Earth’s climate system and the global carbon cycle. It involves the exchange of carbon dioxide (CO2) between the atmosphere, oceans, terrestrial biosphere, and geological reservoirs, and how these fluxes are influenced by and influence Earth’s climate.

Cloud Radiative Effect (Chapter 5): Net effect of two competing processes in which clouds can both 1) trap the outgoing longwave terrestrial radiative flux at the top of the atmosphere to warm Earth and 2) reflect incoming shortwave solar radiative flux back to space to cool Earth. This effect depends on the cloud height, type, and optical properties.

Combustible (Chapter 3): Material that, in the form in which it is used and under the conditions anticipated, will ignite and burn (NFPA, 2021).

Combustion (Chapter 3): Chemical process of oxidation that occurs at a rate fast enough to produce temperature rise and usually light either as a glow or flame.

Combustion Efficiency (Chapter 3): Ratio of heat released by the fuel to the heat input by the fuel. Conflagration (Chapters 3 and 4): Large and uncontrolled fire.

Consumers (Chapter 6): Organisms that obtain energy and nutrients by feeding on other living organisms or their remains. Consumers can be herbivores (feeding on plants), carnivores (feeding on animals), omnivores (feeding on both plants and animals), or detritivores (feeding on dead organic matter).

Displacement (Chapter 7): Forced removal or movement of people from their homes, communities, or regions, typically due to factors such as armed conflict, natural disasters, development projects, or other threats to their safety and well-being.

Earth System Model (ESM) (Chapter 5): Model composed of a set of equations describing atmospheric and oceanic circulation and thermodynamics, incorporating the biological and chemical processes that feedback on to the physics of climate, all solved for a number of locations in space that form a three-dimensional grid over the surface of Earth and underneath the surface of the oceans.

Ecosystem (Chapter 6): Community of living organisms (plants, animals, and microbes) interacting with each other and with the nonliving components of their environment (air, water, and mineral soil), considered as a unit.

Ecosystem Services (Chapter 7): Direct and indirect benefits that ecosystems provide to people and society. These services can include the provisioning of resources such as food, water, timber, and fiber; regulation of environmental quality through water and air purification, flood control, and climate regulation; and cultural and spiritual benefits.

Emission Factor (Chapter 3): Mass of emitted pollutant per mass of fuel burned.

Environmental Effects of Nuclear War (EENW) Researchers (throughout): Include but are not limited to researchers in military planning and analysis; weapons effects modelers; emergency response planners; fire science and engineering; physical Earth systems, climate, and atmospheric sciences; ecosystems; agriculture; trade; and public health.

Equity (Chapter 7): In the societal context, fair distribution of resources, opportunities, and treatment, taking into account the specific needs and circumstances of different individuals or groups.

Evapotranspiration (Chapter 6): Combined process of water evaporation from land and water surfaces, and transpiration from plants.

Exposure (Chapter 7): State of being subjected to something potentially harmful or hazardous. In environmental and health contexts, it typically refers to contact with pollutants, contaminants, radiation, or other agents that may pose health risks.

Fallout (Chapter 7): Residual radioactive particles and materials that are deposited on the ground and in the environment after a nuclear explosion or accident. It can consist of various radioactive isotopes and can contaminate air, water, surfaces, and food sources, posing radiation exposure risks.

Feedbacks (Chapter 7): Interplay between environmental changes and human systems, where impacts on societies can amplify (positive feedback) or mitigate (negative feedback) the initial changes. For example, climate-related disasters can disrupt food production, leading to poverty, conflict, and further environmental degradation—a positive feedback exacerbating vulnerability. Conversely, effective governance and behavioral changes could reduce emissions, slowing climate change impacts—a negative feedback. These complex human–environment interactions can reinforce or counteract climate and environmental pressures.

Fire Dynamics (Chapter 3): How fires start, spread, and develop.

Fire Load (Chapter 3): Total heat energy of the complete combustion of combustible materials in a building, space, or area, expressed in megajoules (MJ) (or its equivalent energy unit). For buildings, it includes furnishing and contents and combustible building elements. There are distributed and localized fire loads. Distributed fire load refers to the overall fire load of the building, space, or area. Localized fire load is the fire load at a specific location; this may have a magnitude that is considerably larger or smaller than the distributed fire load.

Fire Load Density (FLD) (Chapter 3): Heat energy that could be released per unit area by the complete combustion of combustible materials in a building, space, or area, expressed in MJ/m2 (or an equivalent unit indicating heat energy per unit area).

Firestorm (Chapters 3 and 4): Intense conflagration that creates its own convective wind patterns, radially drawing in air near the surface, with strong updrafts above the fire.

Fission-Based Weapon (Chapter 2): Weapon in which part of the explosion energy results from nuclear fission reactions.

Freshwater Ecosystems (Chapter 6): Aquatic environments with low salt concentrations, such as lakes, rivers, and wetlands.

Fuel Load (Chapter 3): Total wood equivalent mass of combustible materials in a building, space, or area, expressed in kilograms (kg) or pounds (lbs) per unit area. Here the heat of combustion of dry wood of 18.6 MJ/kg (or 8,000 BTU/lb) is used as the basis for equivalent wood mass calculation.

General Circulation Model (Chapter 5): Numerical model for computing the evolution of the atmosphere and/or ocean using the fundamental equations that govern geophysical fluid dynamics.

Global South (Chapter 7): Regions and countries in lower- and middle-income countries, primarily located in Africa, Latin America, and parts of Asia.

Governance (Chapter 7): Processes, systems, and institutions through which authority is exercised and decisions are made and implemented within a given entity, such as a government, organization, or community. It encompasses aspects such as policymaking, accountability, transparency, and the ways in which various stakeholders participate in decision-making processes.

Height of Burst (HOB) (Chapter 2): Height above the Earth’s surface at which the nuclear weapon detonates in the air (Glasstone and Dolan, 1977).

Heterogeneous Chemistry (Chapter 4): Ensemble of chemical processes involving aerosol phases (liquid and solid particles) in the atmosphere.

Human Health and Well-Being (Chapter 7): Holistic state of physical, mental, and social well-being, not merely the absence of disease or infirmity. It encompasses various aspects, including physical health, mental health, emotional and psychological well-being, social relationships, and overall life satisfaction.

Hysteresis (Chapter 5): Phenomenon in which the physical response of a system to an external influence depends on both the present magnitude of the influence and the previous history of the system. External influences are often associated with irreversible thermodynamic changes or internal friction, and hysteretic responses are often characterized as lagging. Systems with hysteresis that are driven to evolve from one state to another need not revert to their original state when the driver is removed.

Ignition (Chapter 3): Initiation of combustion.

Lapse-Rate Feedback (Chapter 5): Negative feedback in which a temperature-induced change in Earth’s surface temperature induces a thermodynamically driven change in the rate at which atmospheric temperature decreases with height and thereby alters the thermal component of the greenhouse effect so as to dampen further changes in Earth’s surface temperature.

Longwave (or Infrared or Terrestrial) Radiation (Chapter 5): Electromagnetic radiation emitted by Earth’s surface, atmosphere, and clouds. Longwave radiation lies in the infrared part of the spectrum, with wavelengths typically ranging from 4 to 30 microns.

Marine Ecosystems (Chapter 6): Aquatic environments with high salt concentrations, such as oceans, seas, and estuaries.

Migration (Chapter 7): Movement of people from one place to another, either within a country (internal migration) or across international borders (international migration). It can be voluntary or forced and can occur for various reasons, such as economic opportunities, conflict, environmental factors, or family reunification.

Morbidity (Chapter 7): State of being ill, diseased, or unhealthy. It is a measure of the incidence or prevalence of illness or disease within a specific population over a given period. Morbidity rates are used to assess the burden and patterns of health conditions.

Mortality (Chapter 7): Measure of the number of deaths in a particular population, scaled to the size of that population, over a specified time period. Mortality rates are used to quantify the impact of different causes of death and assess overall population health. Mortality in the aftermath of a disaster can be classified as direct, indirect, and attributable. This categorization can assist in managing and predictive modeling of a nuclear event (Stoto et al., 2021).

Multisectoral Dynamics (Chapter 7): Interconnections and interactions between different sectors or domains, such as the economy, environment, society, and governance. It recognizes that changes or decisions in one sector can have ripple effects and implications for other sectors, and that addressing complex challenges often requires a holistic, cross-sectoral approach.

Net Primary Production (Chapter 6): Rate at which ecosystems convert carbon dioxide and radiant energy into organic compounds through photosynthesis, minus the amount lost through heterotrophic and autotrophic respiration. It provides energy to support consumer organisms in the ecosystem.

Nonlinearity (Chapter 7): Situations in which seemingly small environmental or societal shifts can trigger disproportionately large consequences due to complex interdependencies and tipping points. For instance, environmental changes could eventually render cities uninhabitable, leading to widespread

Particulate Organic Carbon (OC) (Chapter 3): All combustible, noncarbonate carbon that can be collected on a filter (Kharbush et al., 2020).

Particulate Organic Material (POM) (Chapter 3): Total organic matter that is part of measured particulate matter, including carbon, nitrogen, oxygen and hydrogen.

Photosynthesis (Chapter 6): Process by which green plants, algae, and some bacteria use the energy from sunlight, water, and carbon dioxide to produce oxygen and energy-rich organic compounds (such as glucose) that can be used as food.

Photosynthetically Active Radiation (PAR) (Chapters 5 and 6): Total solar radiation at wavelengths between 400 (violet) and 700 nm (red) that is available for photon capture by chlorophyll and other light harvesting pigments in plants, also referred to as photosynthetically available radiation.

Phytoplankton (Chapter 6): Microscopic aquatic organisms that photosynthesize and form the base of the marine food chain.

Polycyclic Aromatic Hydrocarbons (PAHs) (Chapter 4): Consisting of three or more fused aromatic (benzene) rings and produced as by-products of fossil fuel, diesel, fat, and biomass burning. Some PAHs have been identified as carcinogenic, mutagenic, and teratogenic. Three-ringed PAHs occur in the atmosphere predominantly in the vapor phase, whereas four-ringed PAHs can occur in both the vapor and particle phases. Multiringed PAHs with five rings or more are mostly bound to particles and are considered to be very hazardous to human health (Schwela, 2014).

Producers (Chapter 6): Organisms, such as green plants, algae, and some bacteria, that can produce their own organic compounds from inorganic materials through photosynthesis or chemosynthesis, serving as the primary source of energy and nutrients for other organisms in an ecosystem.

Pyrocumulonimbus (pyroCb) (Chapter 4): Extreme manifestation of a pyrocumulus cloud, or clouds generated by the heat of a wildfire, that often rises to the upper troposphere or lower stratosphere (WMO, 2017).

Resilience (Chapter 7): Ability of a community or society to withstand, adapt to, and recover from adverse events or disruptions. It involves factors such as strong social networks, effective governance, and the capacity to learn and transform in response to challenges.

Risk (Chapter 7): In the context of environmental changes, potential for adverse consequences for human or ecological systems, recognizing the diversity of values and objectives associated with such systems. Risks result from dynamic interactions between environment-related hazards with the exposure and vulnerability of the affected human or ecological system to those hazards. Moreover, risks can arise both from potential impacts of environmental change as well as the human responses to environmental change. Societal vulnerability to environmental change includes existing societal and economic conditions, for example, the susceptibility of marginalized communities to economic disruptions or of agricultural livelihoods to drought. Risk is thus substantially shaped by underlying societal factors such as poverty, inequity, governance capacity, and adaptive preparedness.

Rubblization (Chapter 3): Process of a structure being reduced to rubble.

Shortwave (or Solar) Radiation (Chapter 5): Electromagnetic radiation emitted by the sun, which lies in the visible, near-ultraviolet, and near-infrared range of the spectrum. Shortwave radiation typically occurs between wavelengths of 0.1 to 5.0 microns.

Smoldering (Chapter 3): Combustion of a solid without flame, often evidenced by visible smoke. (Note: Smoldering can be initiated by small sources of ignition, especially in dusts or fibrous or porous materials, and may persist for an extended time after which a flame may be produced.)

Smoldering Combustion (Chapter 3): Ignition of combustible material where a transition to flaming combustion does not occur but a charred area indicating locations where embers landed can be observed and involves the exothermic oxidation of condensed-phase materials.

Smoke (Chapters 1, 3, and 4): Airborne solid and liquid particulates and gases evolved when a material undergoes pyrolysis or combustion, and often used as an informal term for a fire-emitted aerosol (NFPA, 2021).

Social Capital (Chapter 7): Networks, relationships, and shared norms, values, and understandings that facilitate cooperation and collective action within and among groups. It encompasses elements such as trust, reciprocity, and social cohesion, which can contribute to the well-being and resilience of individuals and communities.

Soot (Chapters 1 and 4): Black particles of carbon produced in a flame (NFPA, 2021).

Source Term (Chapter 2): For a modeling study of the atmospheric and climatic effects of a nuclear detonation, the initial amounts of particulates and other material released or mobilized into the atmosphere.

Spectral Irradiance (also Insolation) (Chapter 5): Power per unit area (surface power density) received from the sun in the form of electromagnetic radiation.

Stratosphere (Chapter 4): Stable (stratified) layer of atmosphere extending from the tropopause upward to a height of about 50 km.

Surface Mixed Layer (Chapter 5): Uppermost layer of the ocean that has been mixed and hence homogenized by active turbulence.

System (throughout): In the context of this report, a set of interacting elements that can be physical, biological, social, or economic in nature, and which function together as a larger whole. A key attribute of the various systems described in this report (such as the climate system or an ecosystem or societal system), is the deep interconnections and interdependencies that exist between their subcomponents, as well as between individual systems. The complex and unpredictable behavior of natural and human systems arises from dynamic interactions and feedbacks, occurring across scales, that can create cascading effects and unforeseen outcomes in response to an initial shock. A “systems approach” to understanding the environmental and societal and economic effects of nuclear war thus requires us to consider the interconnectedness of the social, economic, political, and environmental factors that create the potential for harm to ecosystems, people, and society.

Teleconnection (Chapter 7): Term used in meteorology and climatology to describe the linkage or correlation between weather patterns or climate anomalies in geographically distant regions. The concept can also be applied to societal dynamics. In this context, societal teleconnections refer to the ways in which events, processes, or changes in one part of the world can have ripple effects or consequences for societies and communities in distant or seemingly unrelated parts of the world, for example, through globalization and social and economic interconnectedness.

Thermocline (Chapters 5 and 6): Layer in a body of water (e.g., the interior of the ocean) with a high gradient of temperature with depth.

Thermohaline Circulation (Chapter 5): Large-scale ocean circulation driven by global density gradients caused by surface heat and freshwater fluxes that affect the density of seawater.

Thermonuclear Weapon (Chapter 2): Weapon in which part of the explosion energy results from thermonuclear fusion reactions. The high temperatures required are obtained by means of a fission explosion (Glasstone and Dolan, 1977).

Trophic Level (Chapters 6 and 7): Position that an organism occupies in a food chain or food web, based on its feeding relationships. The trophic levels include producers (plants), primary consumers (herbivores), secondary consumers (carnivores that eat herbivores), and tertiary consumers (carnivores that eat other carnivores). Higher trophic levels represent organisms at the top of the food chain.

Tropopause (Chapter 4): Natural limit between the troposphere (Greek tropos = turn; troposphere = turning or mixing sphere) and the stratosphere (stratified as opposed to mixed). The tropopause can exist anywhere between about 70 hPa (∼18 km) and 400 hPa (∼6 km), and it is therefore not convenient to use a constant pressure level to describe the tropopause.

Troposphere (Chapter 4): Lowest layer of Earth’s atmosphere in direct contact with Earth’s surface. Most of the weather phenomena, systems, convection, turbulence, and clouds occur in this layer, although some may extend into the lower portion of the stratosphere, immediately above the troposphere. The height of the troposphere varies from about 7 – 8 km (5 mi) at the poles to about 16 – 18 km (10 – 11 mi) at the Equator (Reichle, 2023).

Tropospheric ozone (Chapter 4): Produced from the oxidation of hydrocarbons and carbon monoxide (CO) in the presence of nitrogen oxides (NO_x ≡ NO + NO₂) and sunlight. The net sign of ozone production from formation and loss reactions in the troposphere depends critically on the level of the precursor gas NO_x (or more specifically, the level of NO), which acts as a catalyst in ozone chemistry (Ma et al., 2022).

Upwelling/Downwelling (Chapter 6): In the context of ocean or lake environments, the vertical movement of water, with upwelling bringing cold, nutrient-rich waters toward the surface, and downwelling pushing surface waters downward.

Ultraviolet (UV) Radiation (Chapter 6): Portion of the electromagnetic spectrum with wavelengths shorter than visible light but longer than X-rays that can damage DNA and cellular structures.

Ventilation (Chapter 5): Transport of surface waters into the interior of the ocean.

Vulnerability (Chapter 7): Measure of the degree to which a system, population, or individual is susceptible to and unable to cope with the adverse effects of a hazard or stress. It is determined by factors such as exposure, sensitivity, and adaptive capacity. In the context of climate change, vulnerability encompasses the potential for adverse impacts on human or natural systems due to their degree of susceptibility and ability to adapt.

Water Vapor Feedback (Chapter 5): Positive feedback in which a temperature-induced change in sea-surface temperatures alters the rate of evaporation of water vapor from the ocean surface, thereby altering the amount of water vapor in Earth’s atmosphere and its attendant (and dominant) greenhouse effect, and hence further amplifies the change in sea-surface temperature.

Weapon Yield (Chapter 2): Total effective energy released in a nuclear explosion, usually expressed in terms of the equivalent tonnage of TNT required to produce the same energy release in a conventional chemical-based explosion.

Wildland-Urban Interface (WUI) (Chapter 3): Community that exists where humans and their development meet or intermix with wildland fuel.

REFERENCES