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As global temperatures rise our cities are heating up. And that's actually adding to the problem. For starters, traditional city buildings need air conditioning to keep cool, and the number of air conditioners is set to explode. By 2050, two-thirds of the world's households will have an air conditioner, requiring additional electricity capacity equivalent to the current capacity of the US, EU, and Japan combined. Generating that extra electricity will add to future carbon dioxide emissions. There will also be leakage of refrigerants from individual units to consider, though there are now international agreements in place to phase out the use of hydrofluorocarbons and chlorofluorocarbons in traditional air conditioners.
But simple design strategies such as adding green spaces, planning wider urban streets, and low buildings to increase wind flow through are among other measures that can help to reduce heat gain. Municipalities in areas including Australia, the US, and India have implemented cool roof programmes, where roofs are painted with solar reflective paint, covered in white tiles or white membrane. Cool roofs can stay up to 33 degrees Celsius cooler than conventional materials during peak summer weather.
Last year, Pacoima, a community in Los Angeles, painted 1mn square feet of roads, playgrounds, and basketball courts with a reflective paint, which doesn't absorb as much heat as uncoated surfaces would. Sydney suburb Wilton now insists that all new housing must have room for a tree in the garden to produce shade, while urban climate tech start-up BioShade uses hydroponic systems to grow plants by up to 10 inches a day, helping to accelerate the growth of natural shade in cities.
In Greece, Athens hopes to use a piece of its ancient underground aqueduct to revive 20 wells in the city for purposes such as irrigating new green spaces which are being expanded to alleviate the impact of sweltering temperatures. Meanwhile, new legislation in France means that all car parks with spaces for at least 80 cars will need to be covered by solar panels. As well as providing power the panels will shade the cars, meaning they will require less air conditioning when the owners come to use them.
Keeping cool is not a luxury. Heatwaves kill 12,000 people annually, and almost a third of the world's population faces dangerous temperatures for more than 20 days a year. According to the International Energy Agency, cooling sustainably could save the world from 460bn tonnes of carbon emissions, equivalent to eight years of emissions at 2018 levels. The challenge now is to keep cool without contributing to climate change.
