Dr Laura-Jane Nolan is a carbon consultant and operations director at BOM Systems.

War leaves destruction in its wake – cities levelled, economies disrupted, lives lost. But another cost rarely enters the conversation: carbon emissions.

As the conflict in the Middle East grinds on, the world’s attention remains fixed on geopolitics and the loss of life and infrastructure. Yet the climate impact of modern warfare is largely invisible in both reporting and policy.

Using UK government greenhouse gas accounting frameworks and publicly available expenditure data, it is possible to estimate the emissions generated and the far larger footprint likely to follow during reconstruction.

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According to researchers at Queen Mary University of London, in just the first 14 days, US-Israeli war with Iran generated more than 5 million tonnes of carbon dioxide equivalent (CO₂e). While this represents only part of the total, it provides a rare, quantified entry point into the scale of the environmental damage caused so far.

Let’s be clear, direct measurement is not simple. Military fuel use, logistics and procurement data are rarely disclosed in detail. Researchers therefore rely on spend-based estimates, that is, the amount of CO2 equivalent per pound or dollar spent.

Post-conflict reconstruction

According to Reuters, the United States alone spent at least $11.3 billion (around £8.5 billion) in the first six days of the conflict. Using a conservative estimate of around 0.4 kg CO₂e per pound spent, the first six days of documented operations correspond to roughly 3.4 million tonnes of CO₂e.

After another week of conflict, the conservative estimate of over 5 million tonnes of CO₂e is not a small amount of greenhouse gases. It is roughly equivalent to 1.1 million cars driven for a year – all the cars in a large European city. It is also comparable to a million transatlantic flights.

If this seems shocking, these estimates likely underplay the situation. We haven’t considered the rebuilding of the destroyed buildings and infrastructure yet. Evidence from past conflicts shows that emissions from rebuilding, through cement, steel, asphalt and heavy machinery, can exceed those generated during active combat.

UK government data indicates that every £1 billion spent on construction generates approximately 250,000 to 350,000 tonnes of CO₂e, before accounting for debris clearance and supply-chain disruption.

In policy terms, this should prompt critical questions about how reconstruction should be financed and delivered, as investing in the green economy for new infrastructure will positively shape long-term emissions trajectories. Rebuilding antiquated infrastructure will be good money thrown after bad.

Gap in climate policy governance

Despite this, the climate cost of war remains largely absent from international frameworks. A loophole in the Kyoto Protocol even allowed countries to exclude military emissions from their national reporting. While the Paris Agreement removed Kyoto’s limited, sector-specific reporting rules and its focus on only developed countries – which had enabled greenhouse gases from overseas military activity to be kept out of the equation – military emissions are still inconsistently reported and rarely disaggregated.

This creates a gap in climate governance at precisely the historical moment when the climate system is shifting from predictable, linear change to a regime in which self-reinforcing, potentially irreversible changes will likely occur.

Systematic carbon accounting for conflict and reconstruction using internationally agreed-upon frameworks such as ISO 14064-1 could set a new precedent for environmental accountability. Following Iraq’s invasion of Kuwait, the United Nations Compensation Commission awarded billions of dollars for environmental damage, including oil fires and ecosystem loss. Carbon accounting could support post-conflict environmental assessments and contribute to just liability frameworks and reparations.

Assessing infrastructure finance

International institutions are already moving in this direction. Multilateral development banks increasingly apply climate conditions to infrastructure finance, and post-conflict reconstruction funding could follow similar principles. Embedding emissions accounting into these processes would align recovery efforts with existing climate commitments.

The economic case is also completely clear for most people. The £8.5 billion spent in the first six days of the Iran conflict could have financed large-scale clean energy deployment, solar, wind, electrified heating and transport, delivering long-term returns, reducing fossil fuel dependence and strengthening energy security.

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Unlike military expenditure, these investments generate ongoing economic value. Yet the absence of systematic accounting for all aspects of war means these trade-offs remain largely invisible to policymakers, markets and the public.

As debates grow around recognising ecocide as a crime under international law, the legal and institutional frameworks for addressing environmental harm are evolving. Integrating carbon accounting into conflict and reconstruction processes would be a pragmatic next step, reflecting both climate realities and existing policy trends.

The climate cost of war is not hypothetical. It is measurable, material and increasingly unavoidable. The question is whether it will continue to be ignored.

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Carbon accounting can help tackle the hidden emissions of war