The year 2025 was the third warmest on record on the planet and 95% of Europe experienced annual temperatures above average. With the end of May bringing unusually high temperatures for this time of year —and 84 deaths in Spain attributed to excess heat in that last week—, and with summer just around the corner, cooling and air conditioning systems are an essential tool for adapting to climate change, especially, for the most vulnerable.
However, these devices spark controversy. On the one hand, their environmental impact reinforces the processes that cause the increase in temperatures. On the other, their presence is still limited in public and private spaces. While students and teachers suffer from the heat in many schools in Spain, a portion of the population cannot afford these devices and, above all, their electricity bills.
In this context, the World Health Organization (WHO/Europe) today presented its new guidance on heat and health action plans. It acknowledges the need for a “nuanced policy” regarding air conditioning. On the one hand, it reminds that it is a “non-sustainable” solution. On the other, it highlights the need to ensure equitable access, especially for the most vulnerable.
Air conditioning is the typical example where mitigation, emission reduction, and adaptation come together
Marta Olazabal
“The debate is not air conditioning yes or no, but how to reconcile our needs with current buildings to use systems that are as environmentally friendly as possible,” explained the University of Córdoba researcher and head of the Applied Thermal Engineering Research Group, Manuel Ruiz de Adana, in a recent briefing organized by SMC Spain.
For her part, the head of the Climate Change Adaptation Research Group at BC3 (Basque Centre for Climate Change), Marta Olazabal, emphasized that air conditioning is “the typical example where mitigation, emission reduction, and adaptation come together.” In her view, these three factors “are inseparable and must go hand in hand.”
What effects do air conditioning systems have on the environment?
The goal of air conditioning systems is to transfer heat from an indoor area to the outside. The impact this process has on the environment is threefold.
First, this transfer requires electricity, which translates into an increase in electricity consumption. If the electricity that powers these devices comes from fossil fuels, it will contribute to climate change.
Second, the heat released outdoors contributes to rising outdoor temperatures and fuels the urban heat island effect: “In the surroundings of buildings, heat from cooling systems is a very important factor,” explains Ruiz de Adana.
Finally, the refrigerant fluid used by some of these devices is also a greenhouse gas. In theory, the fluid circulates in a closed loop without escaping. In practice, small leaks inevitably accumulate over the device’s lifespan or if it is not properly recycled. This can directly affect climate change.
“The most commonly used technology is vapor or refrigerant gas compression, which has these three effects,” says Ruiz de Adana. However, “there are many cooling systems, and air conditioning is the minimum level needed for comfort. Complexity levels and requirements increase as the context changes.” An apartment is not the same as an office, nor an office the same as a hospital, even if we group them together.
There are less polluting alternatives
“We know air conditioning has problems, which is why we must also combat the urban heat island effect with green and blue infrastructure and renaturalize our cities, but the key point is that electricity consumption can now be renewable,” says CSIC researcher and climate anthropology expert Emilio Santiago. In other words, “there is an aspect of its traditional unsustainability that we can minimize.”
Ruiz de Adana explains that the energy efficiency of these technologies “has improved greatly” in recent years, but “still has issues to resolve.” In some cases, such as heat expelled from buildings, it cannot be avoided. “Therefore, the more homes are air-conditioned, the more heat will be dissipated around buildings.” Part of it could be reused through aerothermal systems, “a conventional air-based system where heat, normally dissipated outside, is reused, usually to heat water,” he explains. “As these are more efficient next-generation systems, they have low energy consumption and can be combined with photovoltaic systems,” he adds.
Evaporative cooling systems, which are used in schools in Andalusia, consume little energy and are easy to power with photovoltaics, offering a sustainable solution for cooling classrooms
Manuel Ruiz de Adana
Regarding refrigerants, Ruiz de Adana notes there are alternative options to commonly used ones like R32, whose global warming potential is 675 times that of CO2. He mentions CO2 itself and propane as alternatives, whose impact on the ozone layer and climate change is lower, though not nonexistent.
However, he points out that there are alternatives to compression technology, such as absorption, evaporative cooling and renewable district heating and cooling networks, all of them more sustainable.
“Evaporative cooling systems are already used in schools in Andalusia, which implemented a public school bioclimatization plan, and they have minimal electricity consumption and moderate water use,” explains Ruiz de Adana. “Since they consume little, they are easy to power with photovoltaic energy, offering a sustainable solution for cooling classrooms,” he adds.
Meanwhile, renewable district heating and cooling networks have enabled neighborhoods and districts across Spain to adopt fully renewable systems, from Zamora and Burgos to Madrid and Valladolid. “Decarbonizing energy use for climate control is already technologically viable and cost-effective. What’s missing is regulatory support,” says Ruiz de Adana.
Democratizing thermal comfort
According to a survey by the National Statistics Institute (INE), one-third of people in Spain in 2023 reported they could not keep their homes at an adequate temperature during summer, compared to one-quarter in 2012.
In this context, how can access to cooling systems be ensured? Olazabal notes that “families bear the cost of building cooling, while public space is a regional and national responsibility.”
Failing to propose a policy for redistributing air conditioning today is medically irresponsible, socially unjust, and rooted in cultural bias
Emilio Santiago
“We need behavioral, legislative, regulatory responses, passive adaptation, but also a redistributive policy for air conditioning to ensure thermal comfort is a right,” says Santiago.
What about ventilation?
Air conditioning systems also interact with ventilation needs in buildings.
“Ventilation is crucial, as seen during COVID-19, but it is energy-intensive,” says Ruiz de Adana.
Refuges, trees, and architecture: other tools against heat
Strategies include climate shelters, bioclimatic architecture, urban shading, passive renovation, and urban renaturalization.
We have fewer trees and are redesigning streets without considering climate criteria
Marta Olazabal
All experts agree: the debate is not whether to use air conditioning, but how to combine it with other tools as climate change worsens.
