When NATO leaders met last week, they repeated familiar warnings about Russia, China and Iran. But one threat did not make the main agenda – climate change. A new study shows rising temperatures could quietly change how submarines are hunted under the sea.
The summit followed a familiar script. Between calls for bigger defence budgets pushed by US President Donald Trump and talks on threats from Russia and Iran, climate change did not make the priority list.
But military and civilian researchers working with NATO say warming seas could deeply change underwater warfare.
In 1989, The Hunt for Red October hit cinemas. Based on Tom Clancy’s novel, the film told the story of a nearly invisible Soviet nuclear submarine tracked by the US Navy. Sean Connery played the rebel captain, Alec Baldwin the CIA agent trying to find him.
It felt like fiction, but the idea came straight from the US Navy. Finding stealthy submarines has always been a top job for big navies. Now climate change is making that hunt harder.
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Sound as a weapon
Submarines are tracked mainly by sonar. Some sonar sends out sound waves and waits for echoes. Others just listen for noise in the water. Both depend on how sound moves under the sea.
The problem is that sound speed and reach change with temperature, pressure and salt levels.
As the planet warms, oceans heat up, ice melts and billions of tonnes of fresh water mix with salt water. These shifts mess with sonar – the systems cannot “hear” as far as they used to.
A study by the NATO Defence College, led by Andrea and Mauro Gilli in March tested how bad this could get. They used old ocean data from 1970 to 1999 and compared it to climate forecasts for the end of the century, from 2070 to 2099.
They looked at two key places: the North Atlantic, which is vital for NATO, and the Western Pacific, where China is growing its navy.
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Dramatic detection drops
Their results, the study says, are clear and worrying. In the North Atlantic, sonar could lose much of its reach.
Right now, a submarine might be picked up from 60 kilometres away. By the century’s end, that could drop to just 35 kilometres. In the Western Pacific, the drop is smaller but still real – from 10 kilometres to seven kilometres.
These numbers matter for strategy. The study says if submarines get harder to find in the Atlantic, Russia could use that advantage to boost its underwater patrols.
NATO might then have to redeploy more ships and planes back there, at the expense of the Pacific where its focus has been growing.
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A threat multiplier
NATO has already called climate change a “threat multiplier” and has committed to take into account in its activities the necessity of mitigating it. But this is the first time its effect on the core of military operations has been modelled in such detail.
There will be new costs and tech headaches. The NATO Defence College study says navies may need new sonar, more underwater drones or different patrol zones. All of this needs careful planning and more funding.
The researchers call for more teamwork between ocean experts, military engineers and climate scientists – crossing oceanography, military engineering and climatology, a field still little explored.
At the summit last week, Trump and others pushed NATO countries to spend more on defence. But the study says extra money might not just pay for tanks or jets. It could go towards ocean research, smarter sonar and better underwater drones.
For now, navies are only starting to grasp how climate change could reshape underwater warfare. As the seas keep warming, that learning curve could decide how hard it is to find the next real-life Red October lurking beneath the waves.
This story was adapted from the original version in French by RFI’s Simon Roze.
