The climate impact of Donald Trump’s geopolitical ambitions could deepen planetary catastrophe, triggering a global military buildup that accelerates greenhouse gas emissions, a leading expert has warned.

The Pentagon – the US armed forces and Department of Defense (DoD) agencies – is the world’s largest institutional greenhouse gas emitter, accounting for at least 1% of total US emissions annually, according to analysis by Neta Crawford, co-founder of the Costs of War project at Brown University.

Over the past five decades, US military emissions have waxed and waned with its geopolitical fears and ambitions. In 2023, the Pentagon’s operations and installations generated about 48 megatons of carbon dioxide equivalent (MtCO2e) – more planet-warming gases than emitted by entire countries including Finland, Guatemala and Syria that year.