Emissions from the world’s armed forces must be counted and reported, argue researchers in a comment article published by Nature.

The authors, which include Lancaster University’s Dr Reuben Larbi and Dr Kirsti Ashworth, highlight that the US and UK armed forces emit as much carbon dioxide per capitaas many carbon-intensive countries. They contend that military emissions must be officially recognised and accurately reported in national inventories, and that military operations need to be decarbonised.

The military sector’s share of global greenhouse-gas emissionsis estimated to be around 1-5% — comparable to emissions from the aviation and shipping industries. However, militaries have been left out of international agreements to declare emissions since the 1997 Kyoto Protocol, on the basis of preserving national security. A lack of published data makes it hard to estimate totals, and only a handful of forces — including those of the United Kingdom and United States — have published strategy documents on climate action.

Also missing are accurate methodologies for calculating emissions from military activities. For example, recording is near impossible in hostile, fast-changing or insecure locations.

On the basis of available fuel-use data, the authors note that US forces alone — the world’s largest in terms of expenditure — emit more greenhouse gases than many countries, including Peru, Singapore and Switzerland. If it were a nation, the US military would have the highest per-capita emissions in the world (at 42 metric tonnes of CO₂ per staff member).

Authors of the article, led by Newcastle University’s Oliver Heidrich, suggest that the true total could be even higher: factoring in other energy supplies, raw materials, supply chains and equipment manufacturing could drastically increase emissions estimates. Emissions from warfare would add even more. Researchers need to calculate this to understand how armed conflicts impact the climate and to help countries to chart low-carbon recovery pathways.

Dr Larbi, a Lancaster University research associate working on the UKRI Economic and Social Research Council (ESRC) funded Concrete Impacts project, which looks at military supply chains and associated environmental footprints, said: “We need transparency and accountability from all sectors including the military to limit warming to 1.5°C.”

Dr Ashworth, a Royal Society Dorothy Hodgkin Research Fellow in Lancaster Environment Centre, and who also works on the Concrete Impacts project, said: “It’s high time the world’s militaries were held to account for the impacts of their actions on the environment as well as the devastating human and social cost of conflict.

“The window of opportunity to tackle climate change is rapidly closing and it is totally unacceptable that an entire sector be permitted to continue its business as usual carbon emissions.”

The authors of the paper are Kirsti Ashworth and Reuben Larbi of Lancaster University; Mohammad Ali Rajaeifar and Oliver Heidrich of Newcastle University; Stuart Parkinson of Scientists for Global Responsibility; Benjamin Neimark of Queen Mary University of London; Doug Weir of the Conflict and Environment Observatory and Kings College London.