Climate Impact of Wars & Armed Conflicts

Historical & current data through 2024 CEOBS · Brown Univ. Costs of War · UNEP · Conflict and Environment Observatory Excluded from most national GHG inventories

~120 MtCO₂e

Ukraine war est. emissions (Feb 2022–Dec 2023)

~400 MtCO₂e

Iraq War total est. (2003–2011)

~1 BtCO₂e

Vietnam War est. total (1955–1975)

2 MtCO₂e/day

Kuwait oil fires peak rate (1991)

~5.5%

Est. global military share of GHGs (all nations)

Wars as an Invisible GHG Source

Armed conflicts generate greenhouse gas emissions through multiple pathways — direct fuel combustion by military platforms, destruction of infrastructure that must be rebuilt, burning of oil fields, deforestation via bombardment, and the enormous logistical tail of military supply chains. Despite this, conflict emissions are systematically excluded from national GHG inventories under UNFCCC reporting guidelines.

The Conflict and Environment Observatory (CEOBS) and researchers at the University of Sussex have estimated that if the world's militaries were a nation, they would be the 4th–5th largest GHG emitter globally — larger than Germany or Brazil on a combined basis.

Kyoto Protocol loophole: In 1997, the U.S. successfully lobbied to exempt military operations from mandatory GHG reporting, a carve-out that carried through the Paris Agreement's Article 2 national inventory rules. No country is required to report overseas military emissions.

Conflict GHG Pathways

CEOBS "The Environmental Cost of War" (2022); Conflict and Environment Observatory estimates

Direct Combustion

Military vehicles, aircraft, ships, and generators consume fossil fuels at far higher rates than civilian equivalents per unit of productive output. An M1 Abrams tank gets ~0.6 mpg (diesel/JP-8). A B-52 bomber burns ~47,000 litres per hour at cruise power.

Infrastructure Destruction

Destroying and rebuilding urban infrastructure — power grids, water systems, roads, buildings — generates substantial embedded carbon. UNEP estimates rebuilding Ukraine's infrastructure could require 400–500 MtCO₂e in construction-phase emissions alone.

Ecosystem Disruption

Forest fires from bombardment, deforestation for defensive earthworks and fuel, chemical contamination of soil, and displacement of wildlife populations can permanently impair carbon sinks. Vietnam's forests lost an estimated 2.2 million hectares during the war.

Ukraine War GHG Emissions by Category (est. MtCO₂e, 2022–2023)

Korinets et al. (2023) "Estimating the carbon footprint of Russia's war in Ukraine"; CEOBS; Climate Focus

Ukraine War — Key Findings

A landmark 2023 study co-authored by Ukrainian and European researchers calculated the first systematic GHG accounting of the Russia-Ukraine war. Their central estimate for the first 18 months (Feb 2022 – Aug 2023) was approximately 120 MtCO₂e — roughly equivalent to Belgium's annual national emissions.

Key emission sources included:

Infrastructure fires & destruction — largest single category (~33%)
Military operations — vehicle, aircraft, and logistics fuel (~25%)
Industrial facility damage — including Mariupol steel plants (~15%)
Wildfire spread — bombardment-ignited fires in forests and fields (~12%)
Post-conflict reconstruction — estimated forward-looking cost (~15%)

Zaporizhzhia Nuclear Plant: Damage to cooling systems and loss of grid power at Europe's largest nuclear plant throughout 2022–2023 created a radiological risk that, while ultimately contained, adds a potential extreme tail risk to conflict climate accounting not captured in CO₂ metrics.

Annualized Ukraine Conflict Emissions vs. Comparable National Inventories (MtCO₂e/yr)

IEA national inventories 2022; Korinets et al. 2023 annualized estimate

Reconstruction carbon debt: The World Bank estimated Ukraine reconstruction costs at $411B as of early 2024. If built to pre-war rather than net-zero standards, this represents an enormous lock-in of carbon-intensive infrastructure. Ukraine and the EU have committed to "build back better" principles integrating energy efficiency, but financing and wartime urgency create competing pressures.

Historical Conflict GHG Estimates (MtCO₂e total)

CEOBS Historical analysis; Brown Univ. Costs of War Project; Watson Institute; Moran & Russell (2022)

Kuwait Oil Fires (1991)

During the Gulf War, retreating Iraqi forces ignited approximately 700 Kuwaiti oil wells in January–February 1991. At peak, the fires were burning an estimated 5–6 million barrels of oil per day, releasing roughly 2 million tonnes of CO₂e daily — or about 140 MtCO₂e over the ~9-month period until the last fire was extinguished in November 1991.

The fires also released massive quantities of soot, sulfur dioxide, and polycyclic aromatic hydrocarbons. Early climate modelling feared a "mini nuclear winter" effect, but the soot plume stayed largely in the troposphere rather than reaching the stratosphere, limiting the cooling effect.

Hobbs & Radke (1992) Science; NOAA CMDL data; Kuwait Oil Company post-conflict assessment

Vietnam War — Herbicide & Deforestation

The U.S. military's Operation Ranch Hand sprayed approximately 77 million litres of herbicides (including Agent Orange, containing dioxin TCDD) over ~3.1 million hectares of South Vietnamese forest and farmland between 1961–1971. An estimated 2.2 million hectares of mangrove and inland forest were permanently deforested.

Mangrove destruction alone is estimated to have released 100–160 MtCO₂e from soil carbon, while the loss of carbon sink capacity over subsequent decades adds a long tail of climate damage not captured in direct emission figures.

Agent Orange & soil carbon: Dioxin contamination inhibited forest regeneration in many areas for decades, extending both the ecological and carbon accounting of the war well into the 1990s and 2000s.

Conflict Environmental Impacts — Selected Events

Conflict / Event	Period	Primary Environmental Impact	Est. GHG/CO₂e
WWII (global)	1939–1945	Industrial-scale warfare; oil facility bombing; forest clearance	~1.3 BtCO₂e est.
Korean War	1950–1953	Deforestation; oil infrastructure destruction	~50–80 MtCO₂e est.
Vietnam War (US operations)	1965–1975	Herbicide deforestation; B-52 crater landscape; napalm fires	~700 MtCO₂e est.
Kuwait Oil Fires	1991	700 burning oil wells; soot plume over S. Asia	~140 MtCO₂e
Iraq War (invasion & occupation)	2003–2011	Oil infrastructure; generator fuel; DU contamination	~400 MtCO₂e est.
Syrian Civil War	2011–ongoing	Industrial destruction; oil field seizure and burning; displacement	~150–300 MtCO₂e est.
Russia-Ukraine War	2022–ongoing	Infrastructure fires; industrial destruction; wildfire	~120 MtCO₂e (yr 1–2)
Gaza/Lebanon conflict	2023–2024	Urban infrastructure destruction; fuel combustion; reconstruction	~2–6 MtCO₂e (preliminary est.)

War's Impact on Carbon Sinks

Beyond direct emissions, armed conflicts degrade ecosystems that function as critical carbon sinks. This creates a double accounting problem: direct emissions are released and future sequestration capacity is permanently or semi-permanently destroyed.

Categories of ecosystem damage from conflict:

Forest fires from bombardment — artillery and aerial ordnance ignite wildfires, releasing stored forest carbon
Deforestation for military use — clearing fields of fire, building field fortifications, fuel sourcing
Soil contamination — heavy metals, depleted uranium, and ordnance residue impair revegetation
Wetland drainage — draining peatlands and wetlands for vehicle movement releases stored methane and CO₂
Marine ecosystem damage — naval warfare, fuel spills, and port destruction damage coastal carbon sinks (seagrass, mangroves)
Displacement & encroachment — refugee populations displaced into forest margins drive secondary deforestation

Carbon Sink Loss by Ecosystem Type

CEOBS; UNEP "Protecting the Environment During Armed Conflict" (2009, updated 2022); Machlis & Hanson (2008)

Depleted Uranium (DU) & Long-Term Soil Carbon

Depleted uranium penetrators, used extensively in the Gulf War (1991) and Iraq War (2003–2011) by U.S. and UK forces, contaminate soil with radioactive and chemically toxic heavy metals. The UNEP estimates roughly 340–800 tonnes of DU were used in Iraq across both conflicts.

While DU is not a significant GHG source, its soil contamination inhibits plant growth and revegetation, reducing the soil's capacity to sequester carbon and function as an active biological sink. Areas around former battlefields in southern Iraq still show significantly reduced vegetation cover and soil organic matter relative to pre-war baselines.

Long legacy: DU has a half-life of 4.5 billion years. Its primary environmental concern is chemical toxicity (kidney damage) and low-level radioactivity affecting soil microbiomes and plant germination. Full ecological remediation of contaminated sites may be effectively permanent on human timescales.

Protected area impact: A 2018 study in Nature Sustainability found that over 200 armed conflicts occurred within or adjacent to UNESCO-designated protected areas between 1946 and 2010, with biodiversity loss and carbon sink impairment extending well beyond declared war zones. The interaction between conflict and conservation failure compounds the long-term climate cost.

Why War Emissions Are Invisible

Under the UNFCCC framework and Paris Agreement, countries submit national GHG inventories (the NDCs) covering their domestic economy. Several loopholes systematically exclude military emissions:

Voluntary reporting of international military operations (Paris Article 13)
Bunker fuel exclusions — international aviation and marine fuel sold to militaries is often excluded from both the purchaser's and the destination country's inventory
Conflict jurisdiction gaps — emissions from operations in foreign theatres fall outside any national inventory
Classification — operational security concerns restrict disclosure of fuel use and operational tempo data
Weapons procurement exclusion — emissions from manufacturing military equipment (Scope 3) are rarely included

Scope 1/2/3 Framework for Military GHGs

Adapted from Parkinson et al. (2022) "Accounting for military greenhouse gas emissions"

Reform Proposals & Current Status

Proposal	Proponent	Status	Key Obstacle
Mandatory military GHG reporting in UNFCCC inventories	CEOBS, academic researchers	Not adopted	U.S., UK, France opposition; operational security
War reparations include environmental remediation costs	UNEP, some civil society	Partial (Ukraine)	Sovereignty; attribution complexity
NATO/allies harmonised military GHG accounting standard	Some EU states	Discussions ongoing	Lack of political will; data sensitivity
Post-conflict environmental assessment obligations	ILC Articles on Protection of Environment during Armed Conflict	Adopted 2022 (non-binding)	No enforcement mechanism
Carbon offset requirements for military fuel purchases	Academic proposals	Not adopted	Political feasibility; mission priority

Paris Agreement gap: The Paris Agreement's temperature targets (1.5°C/2°C) are based on emission trajectories that assume complete and accurate national inventories. Systematic exclusion of military and conflict emissions means the effective global budget is smaller than official accounting suggests — the accounting gap may represent 4–6% of global annual emissions.