Boiling point

United Nations Framework Convention on Climate Change

The world is getting warmer due to climate change and our cities are warming fastest of all. To many of us, that will come as no surprise: this summer has seen record-breaking temperatures around the world from Ireland to Spain, with a resulting rise in heat strokes and death as cities swelter in this new normal.

And while more and more of us will therefore rely on air conditioning – the International Energy Agency estimates that the energy spent on air conditioning will triple by 2050 – that will only exacerbate the worst effects of the climate crisis.

And of course, many people in the Developing World cannot afford an air conditioner, or even a fan, while millions have no access to electricity, or are subject to daily power outages.

And it is our cities that will bear the brunt of this rise in temperatures, given that – due to the so-called urban heat island effect – they are already 0.5 to 4 degrees hotter than the surrounding countryside.

This is a huge challenge from both a climate and a public health perspective. A 2019 study in The Lancet Planetary Health revealed that more than five million people die each year globally because of excessively hot or cold conditions, and that deaths due to heat are increasing.

And while the only long-term way to reduce the heat of our cities is to reduce our greenhouse gas emissions and therefore start to reverse global warming, there are short-term solutions that can help make our cities cooler and more livable.

Uncover Rivers

Seoul is a huge city of nearly 10 million residents, and one that has seen its greater metropolitan area grow to more than 26 million people. In 2005, the Cheonggyecheon River was restored when an 18-lane elevated highway – on which more than 170,000 cars a day drove across – was removed. The restoration of this part of Central Seoul has had a huge knock-on effect, revitalising a previously unwelcoming part of the city, and reducing temperatures along the stream, making them 3.3°C to 5.9°C cooler than on a parallel road 4-7 blocks away. The project has also increased biodiversity, with the number of plant species increasing from 62 to 308, fish species increasing from 4 to 25 and bird species increasing from 6 to 36.

Paint Roofs White

New York City’s Cool Roofs campaign has seen more than 900,000 sq metres of roofs covered in a white reflective coating, which helps reduce the temperature in the building below by up to 30 per cent. The group claims that every 2,500 square feet of roof painted white reduces the city's carbon footprint by 1 ton of CO2. Other cities encouraging the practice include Chicago and Melbourne, and given its effectiveness, it is a relatively inexpensive heat reduction measure. One 2012 paper from Arizona State University found that white-washed roofs could cut temperatures by 1.5°C in California and 1.8°C in Washington D.C.

Plant Trees

A study published in Nature last year of satellite data from 293 cities in Europe revealed that trees can reduce surface temperature by up to 12°C in some regions, with trees planted in cooler Northern and Central European countries having the most cooling effect. This cooling is mainly the result of shading and transpiration, which is when water is released as water vapour through the leaves.

Build Smarter

Wander through Dubai’s old Bastakiya District and you will see multiple wind towers: an ancient passive cooling system that allows wind to flow through the building below. While this form of architecture has fallen out of favour in an era of glass skyscrapers and air conditioning, recent years have seen more interest in passive cooling architecture and more sustainable forms of building. In short, this architecture uses materials that protect residents from the heat and allow cooling winds to circulate, something that will become ever more important in the coming decades.

Use Water

Water has long been used by cities as a cooling device, and rivers, ponds, lakes and wetlands can reduce urban ambient temperatures by up to 2°C. Fountains can decrease surrounding air temperatures by 3°C and its cooling effect can be felt up to 35 metres away. Of course, in some cities with water shortages, these sorts of solutions are not feasible, but they can be adapted in cities which have suitable water resources.

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