Extreme heat events are threatening the alliance’s plans.
When NATO leaders meet in Ankara, Turkey, this week, the primary focus will be on following through on 2025 commitments to increase defence spending significantly across the alliance. As last month’s record temperatures across Europe have shown, however, the territory NATO defends is now far trickier ground. NATO members must make investments that protect the food, water, transportation, energy, and health systems in the societies in which militaries operate.
Europe is sweltering, and its soldiers are no exception. France experienced its hottest day on record, 44.3 degrees Celsius, and at least 40 people drowned trying to escape the heat, while trains and nuclear plants shut down due to the temperature. Spain, Italy, Germany, and the United Kingdom all broke June records.
As of June 28, the World Health Organisation estimated more than 1,300 excess deaths across the continent since June 21 including around 1,000 in France alone—preliminary counts that officials expect to climb as mortality data firms up over the coming weeks. In the summer of 2022, heat killed nearly 62,000 people across Europe. In comparison, just 6,700 people died globally from terrorist attacks in 2022.
The U.K. Ministry of Defence’s Commander’s Guide to Heat Illness Prevention instructs officers to reconsider physically demanding activity whenever the Met Office issues a red heat warning—the kind seen across England this June. Extreme weather can affect the families and homes of troops, whether through required evacuations, school closures, or home damage, all of which affect troop morale and focus.
But the heat damages more than just people. At the Hague summit last year, NATO members agreed to spend 3.5 per cent on core defence and up to 1.5 per cent on resilience and related security by 2035. Preparing for extreme heat and other climate impacts is key to both. Core defence investments must include requirements matched to a warmer world, while resilience investments must include climate adaptation for critical civilian infrastructure.
Heat hits that infrastructure directly. It buckles and melts runways, bends rails, and makes repairs harder and more exhausting. Britain’s Royal Air Force had to reroute planes to different runways in 2022 when the tarmac on one field at Brize Norton softened in the heat. Hot air is also thinner, so aircraft carry less, take off over longer distances, and climb less easily. The penalty is sharpest for helicopters, expeditionary operations workhorses.
Bastien Alex, a climate advisor to the French military, noted in the defence ministry’s own magazine that above 45 degrees Celsius, militaries must reconsider how helicopters are used in “high heat” theatres. As Alex noted, to fly the same mission in that heat may require two aircraft instead of one—and so an additional pilot, more fuel, and greater logistical support, all of which have to be anticipated and planned. The planning horizon is shifting quickly: A French study found that parts of some high-heat theatres could see 120 days a year above 45 degrees Celsius by 2050, against just five such days a year in the 2020s in the Sahel.
Members must also invest in what I call stability multipliers—the food, water, and energy systems that hold societies together under stress. Shocks brought on by extreme heat in low-income and climate-vulnerable countries can fuel instability, conflict, and displacement, with downstream effects on European security through migration pressures, disrupted supply chains, and increased demand for military and humanitarian engagement.
