In the last weeks of June, Europe experienced a heatwave that broke temperature records from France through to Hungary. The heatwave combined high daytime and nighttime temperatures with high humidity. The result was more than 2,000 excess deaths in France alone.
The third heatwave of the European summer has started.
I have been fascinated by the political and technocratic response to the heatwave because, rhetorically at least, this summer has broken through the background hum of climate change conversations. There is a sense of urgency that I have not heard before. “Panic” is probably too strong a word, but governments are clearly worried. Will Europe be liveable in summer in 10 years time?
Having grown up with hot Australian summers and no air conditioning, I was familiar with the routine. Windows open at night to cool the house. Curtains and windows closed during the day to prevent it heating up. Fans helped. Evaporative cooling only worked if the humidity was not already too high. If it was too high, it didn’t feel like you were cooling, it felt like a sauna.
Where I now live in Europe, domestic air conditioning is not permitted, and the Australian strategies only worked partially in my apartment. Before the heatwave began, the internal wall temperatures were in the low 20s, by the end of the heatwave they were around 28.5. The thermal mass of the building had increased. The concrete and steel had absorbed the rolling heat of the day and radiated it out at night. Sleep was late in coming, patchy, and uncomfortable.
The thermal mass problem tracked something a colleague of mine at icddr,b and I had found in slums in Dhaka, Bangladesh. We had placed temperature data loggers in people’s dwelling and captured the rise and fall of temperature and humidity during the day and night. The construction materials were essentially tin and concrete. A tin roof and tin walls became an oven during the day, but cooled rapidly at night (low thermal mass). A concrete roof and concrete walls (high thermal mass) meant that the building’s internal temperature didn’t rise rapidly during the day, but nor did it cool rapidly at night. The concrete smoothed out the temperature variations, but in the absence of active cooling, it eventually rose to the average ambient temperature.
This is the challenge that Europe faces in a world of much hotter summers. Standard passive cooling techniques will get you only so far. Shade to avoid the direct rays of the sun or solar reflectance (albedo) surface to avoid the impact of direct exposure helps. High emissivity surfaces that radiate heat outwards in the cool of the night. Insulation (thermal resistance) to prevent the heat penetrating. Evaporative cooling if humidity permits and water is available.
In summers of regular heatwaves, however, these techniques are limited. Passive cooling can delay equilibrium, but it cannot overcome it. Eventually the thermal properties of the buildings catch-up. And it is difficult to design the building that sheds heat and never captures heat for a scorching summer, but retains and doesn’t lose heat in the winter. All of this assumes that there is even an option to make massive design changes. The vast majority of European housing stock was built with winters in mind, not summers. The oldest buildings, those that give the historic beauty to European cities, have poor thermal properties, and structural changes to them are heavily restricted by conservation laws.
If one cannot rely on passive cooling, then active cooling becomes the fallback. Historically, there have been very low rates of air conditioning in Europe compared to the United States. The latest heat wave, however, has opened discussion about allowing those in “genuine need” to install air conditioning. This, in itself, opens a can of worms. Who has genuine need? Who will pay for the active cooling for those who need it but cannot afford it. The elderly and those with chronic health conditions are often most vulnerable to heat stress. As groups of people, however, they tend to have less disposable income for the purchase and installation of active cooling. Unfortunately, in a continuous heat-stressed environment, everyone will be in need of cooling.
Widespread European air conditioning will also carry at least two unintended consequences. The first is that air conditioning needs manufacturing and maintaining, and power to run it. This will inevitably have greenhouse gas-production issues for a world that desperately needs to reduce greenhouse gas emissions. The second is that, if one is cooling the inside of a building, one is inevitably dumping heat into the outside. And it is slightly worse than that, you cannot move heat from inside to outside a building cost free, you must generate some additional heat to do that. Large scale air conditioning in cities can raise the external air temperature between 1 and 2 degrees, and it creates a feedback loop, because additional internal cooling is needed to overcome the increase in the rising external heat. The consequence for those who do not have air conditioning (those without “genuine need” or those without homes) is that they will experience even more extreme heat waves so that others may suffer less.
Will Europe be liveable in the summers in 10 years time? It really depends on what you mean by “liveable”. The dead trees I have seen– already unable to survive a June heatwave–do not augur well (see the related article on an iconic English oak tree). Passive cooling will help, but as the thermal mass argument demonstrates, it will be insufficient–the second law of thermodynamics prevents it. The answer Europeans seem to be reaching for is air conditioning–for those who can afford it. The heat it dumps outside falls on those who cannot, just as the emissions it produces fall on everyone, everywhere, including places already less able to cope. Widespread air conditioning does not solve Europe’s heat problem. Change nothing about how we live, and shift the cost onto those with the least capacity to bear it.
