Investing more in the military is not a solution to climate change, and may cost us our security, warn experts in The BMJ's climate issue today.
In the first article, Neta Crawford at the University of St Andrews says the view that climate change is a "threat multiplier" that may cause instability and provoke conflict is leading governments to justify higher defence spending.
Yet while the impacts of climate change are becoming as deadly as war, this perspective ignores how war and day-to-day military activities, such as powering bases and energy for training and mobility, are themselves climate change multipliers.
For example, annual greenhouse gas emissions by the US Department of Defence are larger than the annual emissions of many countries. Arms industries are another major source of emissions, while wars themselves cause large spikes in emissions, especially when the targets include oil and natural gas infrastructure.
Although there is an enormous source of military emissions that can be reduced, Crawford argues that "substantial emissions reductions will occur only when armed forces reduce their overall size and footprint and transition to lower emitting doctrines, including those that do not require long range aircraft missions."
"Rather than take money from health, the environment, and the energy transition to fund the military, we need to spend more on those things," she argues. "While some form of defence is required, the focus should shift to how to ensure effective defence at lower emission levels and reduced costs."
Increasing defence expenditure may also cost us our security, warn Mohammed Abba-Aji at Washington University and Nason Maani at the University of Edinburgh, in a second article.
They note that world military expenditure reached $2887bn (£2182bn; €2575bn) in 2025, nearing 2.5% of world output, while official development assistance fell to $174bn in 2025, the largest annual reduction on record.
Yet as nations divert larger proportions of their budgets to military uses, there is less available for climate, education, and other core human needs.
Not only does this situation have long term implications for health, it also creates a reinforcing loop, where climate stress triggers resource conflicts that justify increased military spending, which in turn diverts funds away from measures that could interrupt such a cycle, they warn.
And although wealthier governments may not be directly involved in these conflicts, by supplying the arms that sustain them while cutting aid to the affected states, they help create the conditions for the instability, they add.
True security must look different, they say. Trade-offs between military and social spending should be weighed for their health and climate implications, and governments should allocate a share of their security funding to climate adaptation, especially in vulnerable regions.
"Governments will continue to invoke their first duty, that of protection, and they should. Protection, however, cannot mean protection from aggression alone. It must extend to protection from the effects of climate change, protection for health, and protection for the environment," they conclude.
