How can we adapt our cities to combat worsening heatwaves?

Cities are under threat from extreme temperatures with heat waves projected to increase in frequency, intensity and duration. What does this mean for the future of our cities and their inhabitants?

The residents of Western Sydney, Australia, will have breathed a collective sigh of relief when summer officially ended on February 28, 2021. The previous 2019/20 summer was the country’s hottest on record and there were fears of another scorcher.

Instead, Australia experienced its coolest summer in nine years with above average rainfall. But the lull in temperature was due to the temporary cooling effect of La Niña, the counterpart of El Niño, that cools large parts of the Pacific Ocean surface. Hotter temperatures will return.

Western Sydney is 6-10°C (11-18°F) hotter than the eastern side of the city during the summer. The number of days per year over 35°C (95°F) has increased from an average of 9.5 in the 1970s to 15.4 days in the last decade. By 2090, days over 35°C (95°F) could more than triple to 52 days.

At these temperatures, the body’s ability to regulate its internal temperature is compromised. This can result in heat cramps, heat exhaustion, heatstroke as well as other illnesses. And, ultimately, death.

According to the World Health Organization, more than 166,000 people died due to heatwaves between 1998-2017. For example, in both Australia and the U.S., extreme heat is responsible for more deaths than any other natural hazard.

Even relatively cooler regions are at risk as their lack of experience with extreme heat often makes them more vulnerable. In the UK, for example, heat waves caused 2,556 deaths in summer 2020, while the 2010 heat wave in Moscow led to 11,000 deaths.

One of the most significant heat waves swept Europe in the summer of 2003. It was the deadliest natural disaster to hit the continent in 50 years with a death toll that exceeded 30,000 – with half of that figure accounted by France alone.

One reason Western Sydney is disproportionately affected by heat is that it is located far from the cooling breeze of the sea. But it also suffers from the urban heat island effect – a phenomenon where cities are warmer than surrounding rural areas due to the built environment and heat generated from vehicles and other sources.

“Western Sydney is a highly urbanized environment covered in concrete and asphalt from its industrial developments, roads, housing and parking lots. This absorbs and retains an immense amount of heat, which exacerbates the urban heat island effect,” explains Raymond Hui, Zurich’s Principal Risk Engineer for Natural Hazards & Climate Change Resilience, Australia/APAC. “The problem is made worse as the cooling tree canopy has been cleared to make way for further high-density development.”

The problem goes way beyond Sydney. There are 354 cities around the world home to 200 million people that experience summer temperature highs over 35°C (95°F), according to research from the Impact 2050 project. Due to global warming, these figures are expected to rise to 970 cities with 1.6 billion people by 2050.

Heat waves put pressure on essential services such as health, water sanitation and transport infrastructure. “One example is power failure resulting in shortages or even blackouts,” says Amar Rahman, Global Head of Climate Change Resilience Services at Zurich Insurance Group.

“The entire power infrastructure loses efficiency during periods of extreme heat, especially if they need water for cooling from rivers that may be both drying and warming up. Power transmission lines have a diminished capacity, and equipment like transformers and inverters see a higher failure rate. But at the same time, electricity demand soars as millions of air conditioners blast at full force,” explains Rahman.

Heat waves are also an economic drain as they reduce productivity. This is particularly true in predominantly outdoor industries like construction and strenuous industries such as manufacturing. It is estimated this causes an 8-22 percent reduction in output that will cost the global economy USD 2.5 trillion a year by 2030.

So, what’s the answer? “Adaptation,” says Rahman. “Cities need to plan for heat waves and educate their residents about how to stay safe during extreme heat. Businesses need to adapt their buildings, infrastructure and working hours to higher temperatures. This may be costly but retrofitting buildings and upgrading equipment will not only reduce demand on infrastructure, but also protect the workforce.”

Many cities are now adapting for extreme heat. Some have regulations to ensure buildings are constructed with heat-reflective materials and greater insulation to optimize air-conditioning. Others are planting more greenery, replacing tarmac from playgrounds with less heat absorbent materials, or introducing cool roofs – which is often simply the case of painting a roof white to reflect heat.

Berlin, for example, aims to become a ‘Sponge City’. It is replacing hard surfaces with green space and water-permeable surfaces to combat the urban heat island effect while also building flood resilience. It plans to introduce more trees, urban wetlands, shaded sidewalks, heat-resistant road surfaces, light-colored buildings that reflect heat, and living rooftops covered in moss and grasses.

Preparedness is also important. Many of India’s cities, such as Ahmedabad, have a ‘Heat Action Plan’ that incorporates adaptive measures, a health care response, awareness campaigns and regulations on outdoor working hours, for instance.

Following the 2003 heat wave, France introduced a national heat wave plan comprising forecasting, warnings and education – such as reminding people to drink water and avoid outdoor exercise. It can quickly mobilize the country – from schools to local pharmacies – to respond, for example, by ensuring care homes provide a ‘cool room’ for residents.

But not all cities are taking appropriate action. In a 2021 survey of 812 global cities by the Carbon Disclose Project, it found that 43 percent of cities do not have an adaptation plan to tackle climate risk. With one in four cities citing budgetary restrictions as a barrier to adaptation.

One of the challenges is that – unlike emissions action – the benefits from adaptation and resilience do not provide an immediate return unlike investment in renewable energy, such as solar panels. While even energy efficiency projects can quickly provide savings.

But one of the biggest challenges remains awareness. “Heat waves are highly dangerous natural hazards, but they rarely receive adequate attention as their death tolls and destruction are not always immediately obvious,” says Belinda Bates, Senior Manager for Climate Change Resilience Services.

“We categorize and name hurricanes and typhoons to communicate their danger and severity. In parts of the world, like California, people prepare for the next big earthquake. But we don’t have the same level of awareness and preparedness for heat waves. That needs to change,” adds Bates.

For Western Sydney, some big decisions lie in wait as temperatures continue to rise. From investing in adaptation and preparedness to even naming heat waves or introducing a heat-risk rating and warming system as Australia has done with bushfires.

But radical and urgent action must be taken. Otherwise, Western Sydney, along with hundreds of other places around the world, might become undesirable and potentially uninhabitable.