Spending on the world’s militaries is climbing rapidly. Dr Stuart Parkinson summarises SGR's major new report examining how this rise is affecting carbon emissions.
Article for Responsible Science journal, no.8; online publication 16 September 2025
War is on the increase. From Ukraine to Gaza, and Sudan to Yemen, military action is creating devastation. This drives – and is being driven by – massive increases in military spending. Since militaries are fossil fuel-hungry – both directly and indirectly – this is exacerbating the climate crisis. But data on military carbon footprints is poor, so governments can avoid responsibility. However, a new report is shining much needed light on the subject.
Military spending surge
In 2024, global military spending reached a staggering $2,700,000,000,000 – 9% higher than the year before, once inflation is factored out. This is the highest level since at least the end of the Cold War – and perhaps during it as well. The United Nations has pointed out that this is similar to the total Gross Domestic Product (GDP) of all African nations – and about 13 times the size of foreign aid provided by wealthier nations to the Global South.
But current trends mean this level of spending is set to rise even further in the coming years. For example, during the summer, NATO – the 32-nation military alliance led by the USA, and including the UK – set a new spending target. Its member nations committed to increase core military spending from the current average of 2.0% GDP to 3.5% GDP with a further 1.5% to be spent on additional ‘security’ measures. NATO accounts for about 55% of the world’s military spending, so this will represent a substantial increase for the global total – and, of course, will trigger further military spending increases in other parts of the world.
Aside from fuelling arms races, further increasing the risk of war, and diverting resources away from urgently needed efforts to tackle poverty, inequality, and the climate and nature emergencies, what will be the effect of these military spending rises on carbon emissions?
Militaries are high carbon
Militaries, arms corporations, and wars themselves are high carbon. Warships, combat planes, and tanks are uniquely fossil fuel-hungry. Military equipment relies on supply-chains of high carbon materials such as steel, aluminium, and ‘rare earth’ metals. Wars destroy carbon reservoirs, from oil and gas storage facilities to forests and wetlands. The global carbon footprint of the military – including armed forces and their supply-chains, but not the impacts of war itself – is estimated to be about 5.5% of global emissions.
Military spending rises will increase these emissions. However, the exact relationship between military spending and military carbon emissions is highly complex and not easy to predict. For example, will extra funding be mainly used to increase military activity, leading to rises in fossil fuel use by combat planes or warships? Or will the funding be used to expand the numbers of military personnel, leading to rises in energy consumption at military bases, or the construction of new bases? Or will extra money be mainly directed towards expanding arms production, leading to higher energy consumption in industry or in the production of high carbon raw materials? Extra carbon emissions in the supply-chain could occur outside the home nation, making them harder to track. Then there is also the issue of additional global heating effects due to non-CO2 emissions from aviation in the stratosphere.
How big will carbon emission rises be?
These complexities have led to burst of research activity attempting to understand and predict how carbon emissions vary with military spending levels. A new review report – written by myself and published by Scientists for Global Responsibility – has assessed the findings of 11 studies from the past two years that have tried to estimate how military spending rises will impact carbon emissions.
Our review concluded that a standardised spending rise of $100 billion will lead to an increase in the military carbon footprint of approximately 32 million tonnes of carbon dioxide equivalent (tCO2e). However, the uncertainty in that figure is high – due to limited data on military emissions and the complexities described above. Thus, the figure for the emissions increase could be as high as 59 million tCO2e.
Applying this analysis to a specific case, we found that the increase in NATO’s military spending over the five years, 2019-24 has led to an increase in its military carbon footprint of about 64 million tCO2e – similar to the territorial emissions of Bahrain. Furthermore, the planned increase to hit the 3.5% GDP spending target is likely to lead to an additional rise of about 132 million tCO2e – more than the territorial emissions of Chile.
It is important to note that these are single-year totals and so, if spending is maintained at higher levels as currently planned, there will be a major cumulative impact of emissions on the climate system. For example, ten years of extra spending by NATO (above 2024 levels) would add about 1,320 tCO2e – equivalent to the annual emissions of the whole of Brazil.
And these estimates do not include emissions due to the impacts of war-fighting, such as destruction of carbon reservoirs or post-war reconstruction.
Reducing uncertainties and reducing emissions
As mentioned, the uncertainty in these estimates is high. Hence, one key recommendation of the report is that measuring and reporting of direct and indirect military carbon emissions are greatly improved, so that the changes resulting from military spending rises can be adequately monitored.
However, despite the uncertainties, the research is unequivocal in highlighting that much stronger efforts are needed to reduce the military carbon footprint. This is not a message that militaries and militaristic governments want to hear. Even when they accept that there is a problem, they favour efforts to develop ‘greener’ weapons systems. Putting aside the serious ethical conflicts associated with this path, there are huge technical obstacles. Civilian decarbonisation researchers point to several sectors which are ‘hard-to-abate’. These include aviation, shipping, trucking, iron and steel, aluminium, and synthetic chemicals. The military is – in technological terms – an amalgamation of these sectors, meaning that it is the hardest of the hard-to-abate sectors.
The need for peace
This emphasises the urgent need to prioritise peace-building efforts in global affairs. Much greater use of diplomacy, mediation, and trust-building are essential. The importance of more arms control and disarmament measures is undeniable. One more hopeful finding from our report is that, when military spending is cut, emissions tend to fall at a faster rate than they grew, because the least energy-efficient technologies tend to be retired first.
But the latest assessment by leading climate scientists is bleak. They say that the Paris 1.5°C target will be breached within a few years without “immediate, transformative action… to reduce emissions”. 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. We must be louder in our calls for peace.
Dr Stuart Parkinson is executive director of Scientists for Global Responsibility, a post he has held for over 20 years, where he has co-ordinated research, education and campaigning on ethical issues across science and technology. He holds a PhD in climate change science, has been an expert reviewer for the Intergovernmental Panel on Climate Change, and has written several influential reports on military carbon emissions.
This is a slighted edited version of an article first published in The Ecologist.
Also see...
SGR project page: Climate change and the military
