One billion people will be living in insufferable heat by 2050. As cities battle rising heat, they are experimenting with a range of innovative solutions to keep their residents cool.

By mid-century, 65% of people will live in cities and the urban population affected by heat will increase by 800%, with more than 970 cities experiencing average summertime temperature highs of 35 ̊C. Today just 354 cities are that hot, according to C40 Cities, a coalition of almost 100 cities working to address climate change.

People living in cities are particularly at risk because of the ‘urban heat island effect.’ Urban areas are warmer than surrounding rural regions due to traffic fumes and dark building materials, explains Regina Vetter, who leads the Cool Cities Network at C40 Cities.

"The people who are most vulnerable to extreme heat are also most vulnerable to Covid-19"

Heat stress can cause many different health problems, ranging from dehydration and heat stroke, to serious cardiovascular and respiratory diseases. It also increases mortality rates. “Heat pushes the deaths of people with chronic diseases forward,” said Kristie Ebi, a professor of Global Health at the University of Washington who studies the health risks of climate change.

The double threat of coronavirus and heat this summer is a major concern, according to Ebi.

In response to the pandemic, New York City has launched the ‘Get Cool’ programme with the aim of installing 74,000 air conditioners in the homes of low-income elderly residents this summer.

“Climate change and coronavirus have been on a collision course this summer. The people who are most vulnerable to extreme heat are also most vulnerable to Covid-19,” said Jainey Bavishi, director of the mayor’s office of resiliency.

Outdoor workers, pregnant women, children, the homeless and elderly are particularly vulnerable, but Ebi says that with the right measures and warning systems in place “all heat related deaths are preventable.”

Cities started taking the issue of heat stress seriously in 2003 after a devastating heat wave caused more than 70,000 deaths in Europe.

In many cities, the hottest areas tend to be the poorest. “Heat is an equity issue,” said Vetter. “A lot of the vulnerability lies in how we are building our cities because it is the lack of green spaces in low income areas that make heat risk higher or it’s to do with not being able to afford air conditioning.”

One way cities can protect their most vulnerable residents is by building a network of ‘cool islands’, including public swimming pools and parks, and communicating their location to people during a heatwave, according to Vetter.

Clear communication about the dangers of heat is key, Ebi agreed. “There is a misconception that people who grew up in warmer areas are more resistant to heat. But Arizona has the highest mortality rate [from heat exposure in the United States],” she said.

To understand which communities are worst affected, many cities have started creating heat maps, which pinpoint where the vulnerabilities lie and adaptation programmes should be targeted.

Cape Town has mapped the entire city to highlight which areas are most vulnerable. “Areas with the lowest resilience to [heat] shocks tend to be impacted by a wide range of underlying societal stresses such as poverty, unemployment, and food insecurity. In Cape Town these vulnerabilities are most acute within informal settlements,” said Craig Kesson, the city’s chief resilience officer, adding that Cape Town is in the early stages of designing a city-wide heat plan.

New York has identified the south Bronx, northern Manhattan and central Brooklyn as the most vulnerable areas, using a [heat vulnerability index](http://a816-dohbesp.nyc.gov/IndicatorPublic/VisualizationData.aspx?id=2191,719b87,107,Summarize#:~:text=The%20New%20York%20City%20(NYC,or%20death%20differs%20across%20neighborhoods.&text=Differences%20in%20these%20risk%20factors,in%20past%20and%20present%20racism.). As part of its $106 million ‘Cool Neighbourhoods’ programme, New York has matched vulnerable people in these areas with volunteers, who check in during a heatwave.

The aim of the programme is “to increase social cohesion and take care of New Yorkers inside their homes,” said Bavisihi.

Cities can protect their most vulnerable residents by building a network of ‘cool islands’

Experts say it is important to minimise the use of air conditioning in urban design, as this leads to a huge surge in energy demand and contributes to global warming. Environmentally friendly cooling solutions range from planting trees and creating green spaces to painting roofs with reflective white paint.

New York has painted 10 million square feet of rooftops white to keep buildings cool as well as offset greenhouse gas emissions. The Cool Roofs reduce air conditioning costs by 10-30% and internal temperatures by up to 30%, making it both an equity and climate adaptation programme, said Bavishi.

Cape Town has invested in recreational spray parks which help keep children cool. These parks are highly water-efficient, using 90% less water than swimming pools - a priority for a city which famously almost turned off the taps in 2018. These parks are free, open to all and tackle the city’s water shortage issue, Vetter noted.

Colombia’s second-largest city, Medellin, has embraced nature as a cooling solution. The city has transformed 18 roads and 12 waterways into ‘Green Corridors.’ As part of the $16.3 million project, 75 residents from disadvantaged backgrounds were trained to become city gardeners and hired to plant almost 10,000 trees. The corridors have reduced the surface temperature in Medellin by 2-3 ̊C and have also improved air quality and biodiversity, the city’s environmental secretariat explained. – Isabelle Gerretsen

(Photo credit: Sophia Gabrielle/Unsplash)