Europe is once again coping with an intense summer. All around the continent, soaring temperatures felt not only uncomfortable but also dangerous. An early heat wave has been linked to more than 10,000 excess deaths. Power cuts have left people sweltering when cooling was most needed. Wildfires, on the other hand, once treated mainly as a Mediterranean threat, have broken out in England, France, Italy, Spain and Sweden while record temperatures have reached as far north as Denmark. The geography of European climate risk is changing faster than the infrastructure built to manage it. Air conditioning is one of the clearest examples of this new vulnerability.

For decades, much of Europe treated cooling as something it could live without. Homes were designed to retain heat during long winters, not to remain cool during prolonged heat waves. Still, air-conditioning ownership across the continent remains around 20%. Yet, prolonged heat waves are turning cooling into a public-health necessity, especially for older people, children and those living in poorly shielded urban housing. The problem is that as millions of Europeans turn to electric cooling, demand rises to new highs, strains power grids and exposes vulnerabilities in critical infrastructure. This is the central paradox of Europe’s hotter summers: Climate change is increasing electricity demand while weakening parts of the energy system.

High temperatures reduce the efficiency of thermal power plants and transmission networks. Drought lowers hydropower production. Warmer rivers and declining water availability can limit the operation of facilities that depend on water for cooling. Wildfires can also damage transmission lines and other critical infrastructure. Extreme heat is therefore no longer only an environmental or public-health concern; it has become an energy security issue.

For years, Europe’s energy security agenda was built around a familiar set of concerns: natural gas supplies, geopolitical tensions and winter shortages. The energy crisis following Russia’s invasion of Ukraine reinforced that focus and accelerated efforts to diversify supplies and expand renewable energy. Those measures were necessary, but they also revealed a blind spot. Europe prepared extensively for cold winters, yet far less attention was paid to the risks of increasingly hotter summers.

This is not simply a policy failure in Brussels. Energy remains one of the most sovereign policy areas within the European Union. While climate objectives are largely coordinated at the EU level, decisions on generation portfolios, nuclear energy, grid investments and capacity planning continue to be taken primarily by national governments. Not surprisingly, member states still view energy as a matter of national security. As a result, common climate ambitions have often advanced faster than the resilience of national energy systems.

Europe has also tended to focus on what is easiest to measure and announce: another gigawatt of renewable capacity, another emissions target or another deadline. These indicators remain important, but they do not show whether hospitals, homes and electricity grids will continue to function during the hottest days of the year. Resilience is less visible and harder to celebrate politically. Yet, it is resilience that determines whether an energy system can withstand a crisis. Therefore, Europe must invest not only in new generation capacity, but also in stronger grids, storage, efficient cooling and cross-border interconnections. Climate-sensitive building standards, improved water management, urban shade and early-warning systems must become part of the energy transition as well. The goal should not simply be to produce cleaner electricity. It should also be to keep that electricity available when extreme weather places the system under its greatest pressure.

Nuclear energy belongs in this discussion, but not as a simple defense of existing technologies. If Europe intends to rely on nuclear power for stable and low-carbon electricity, new plants must be designed for the climate in which they will operate. They will need more resilient cooling systems, lower dependence on vulnerable freshwater sources, passive safety technologies and greater operational flexibility. These features will increase upfront costs. However, they should be seen as long-term insurance for energy security. Building cheaper infrastructure that repeatedly loses output during heatwaves may ultimately prove far more expensive.

This debate is likely to become even more relevant as preparations continue for COP31. For many years, developing and least developed countries have argued that climate finance should not focus solely on emissions reduction and clean energy deployment, but also on strengthening resilience against climate impacts. Their call has often struggled to receive the same political attention as mitigation targets. Europe’s recent experience today demonstrates why that balance can no longer be ignored. Climate resilience is no longer a challenge confined to the Global South; it has become a shared global need.

Perhaps this is the lesson policymakers should take from this summer. The success of the energy transition will not be measured solely by how quickly electricity is decarbonized or how many renewable projects are commissioned. It will also depend on whether energy systems can continue operating safely and reliably when climate extremes place them under their greatest stress. The next phase of the energy transition is not only about producing cleaner electricity but also about building energy systems resilient enough to withstand a hotter world.