Today, cities like Madrid and Miami are among the most desirable cities to live in. But, due to global warming they could become uninhabitable within a few decades.
The Spanish capital recorded its first heatwaves in 40 years a few months ago when the mercury column exceeded 40°C already in May. According to scientists, by 2050 citizens will see increases in maximum temperatures of up to 5°C. Which will trigger more frequent and intense episodes of fires, droughts and floods.
Miami’s existential threat is very different, as it relates to sea-level rise. A recent report by the Urban Land Institute warned that by 2040, more than $3 billion of city property could be lost due to daily tidal flooding.
Global warming: one in three people are exposed to deadly heatwaves
But Madrid and Miami are not alone. Today, about 30 per cent of the world’s population, mostly city dwellers, are exposed to lethal heat events at least 20 days a year. And the outlook is very bad. Even if we stopped carbon emissions today, global temperatures would take a long time to fall permanently. This is because about half of the CO2 emitted in the past will remain in the atmosphere for a long time. And will continue to warm the planet.
The Intergovernmental Panel on Climate Change (IPCC) estimates that global warming will continue for at least another 100 years or so at the level reached when emissions are completely halted. So we are already way behind schedule.
Urban cooling projects
Some countries like Singapore are already investing in major adaptation projects. Among them is ‘Cooling Singapore’. I this project researchers from the ETH-Singapore centre are tackling ways to mitigate the challenges of urban heat.
Currently in phase three, the project has already developed 80 measures to reduce urban heat. In dealing with urban heat, it is important to know that heat stress is generated not only by high temperatures. But also by humidity.
In fact, not many people know that high temperatures alone are rarely fatal. It is the combination of high temperatures and humidity that becomes fatal for humans. This is because at high humidity the body’s ability to cool itself by sweating is greatly reduced. This is why scientists monitor the wet bulb temperature, which accurately measures both heat and humidity.
What is the wet bulb?
The wet bulb temperature represents the minimum temperature that a water-saturated body can reach through evaporative cooling. If this level is too high, the human body cannot cool itself and risks dying of hyperthermia.
Meteorologists and scientists have established that humans cannot survive for more than a few hours in the shade, even with unlimited water, at a wet-bulb temperature of around 35°C.
Fortunately, such conditions are very rarely reached in today’s climate. But absolute climate change could push a number of regions, especially in highly populated areas, into this range.
To effectively cool a building, therefore, it is important not only to reduce heat but also to lower humidity.
Buildings that fight humidity
The ETH-Singapore Centre has developed an innovative building design. It first removes heat from inside the building and then removes moisture from the outside air.
In its ‘3for2’ design, the functions of cooling and dehumidification are split. In fact it is more efficient to cool a building at a higher temperature than that required for dehumidification. Doing so, air distribution inside the building becomes superfluous and the compact units can be integrated into the façade or floor.
Compared to a standard ‘green building‘ this approach offers 20 per cent more office space. It also reduces energy consumption by 40 per cent and requires 16 per cent less building materials.