A sharp rise in NATO military spending could drive global greenhouse gas emissions up by 1,320 million tonnes over the next decade, on par with the annual emissions of Brazil, according to a new report by Scientists for Global Responsibility (SGR).

Military spending tied to climate impact

The study, which reviewed 11 academic papers, found that every $100 billion in additional defense spending generates an estimated 32 million tonnes of CO2 equivalent (tCO2e). These emissions stem from direct sources, such as fuel-intensive combat aircraft, warships, and armored vehicles, as well as indirect sources, including global supply chains, logistics, and the effects of active conflict.

“Military activity is fossil-fuel intensive, yet data on emissions remains patchy or non-existent,” the report noted.

NATO spending plans spike emissions

In response to the war in Ukraine and warnings from US President Donald Trump about weakening alliances, NATO plans to raise military spending to 3.5% of GDP, with a broader 5% target for security expenditure.

Meeting this target would release an extra 132 million tonnes of CO2 equivalent, roughly equal to the annual output of 345 gas-fired power plants or the entire oil-producing nation of Oman.

This comes on top of the $200 billion boost in military budgets between 2019 and 2024, which already increased NATO’s carbon footprint by an estimated 64 million tonnes.

Military carbon footprint outpaces aviation and shipping

Military emissions accounted for about 5.5% of global emissions in 2019, more than the combined contribution of civilian aviation (2%) and shipping (3%), even before factoring in the climate costs of war and reconstruction.

Since then, global military expenditure surged to $2.72 trillion in 2024, the highest since the Cold War. "Israel" recorded the largest budget increase worldwide at $46.5 billion, amid its wars on Gaza, Syria, Iran, Yemen, and Lebanon. In the US, the Pentagon’s 2026 budget is set to reach $1 trillion, a 17% jump driven by Trump’s tax and spend bill.

Experts warn of climate breakdown

“It is extremely difficult to see how the current and planned military spending increases can be reconciled with the transformative action necessary to prevent dangerous climate change,” said Dr. Stuart Parkinson, author of the report.

The findings suggest that unchecked rearmament will play a major role in breaching the Paris Agreement target of limiting warming to 1.5°C.

Recommendations for transparency, decarbonization

The report urges governments spending more than 0.5% of GDP on defense to:

1. Mandate robust reporting of military emissions to the UN;
2. Account for conflict-related greenhouse gases;
3. Transition off fossil fuels through technology, diplomacy, arms control, and disarmament initiatives.

“There is an urgent need for rapid decarbonisation to prevent the most dangerous effects of climate change. But recent and planned rearmament programmes and wars are pushing the world in the opposite direction,” Dr. Parkinson warned.