Silent Killer Part 2: How Cities Are Bracing For More Heat

Extreme heat, a direct cause of climate change, is spreading rapidly across the world, affecting billions of people. With the Intergovernmental Panel on Climate Change (IPCC) warning that further warming will increase the intensity, frequency and duration of heatwaves, cities have begun testing warning systems and other adaptive measures to keep individuals safe, with mixed results.

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This is part 2 of a three-part explainer series on extreme heat. Read part 1 and part 3.

Climate change is escalating extreme heat everywhere in the world. According to a recent analysis by non-profit Climate Central, between May 2023 and May 2024, an estimated 6.3 billion people – roughly 4 out of 5 people in the world – lived through at least a month of what in their areas were considered abnormally high temperatures. Human-made anthropogenic climate change made this extreme heat at least two times more likely to occur, the non-profit found.

Heat affects everyone and is becoming harder to ignore, particularly for those living in urban areas. A 2021 study concluded that by the end of the century, cities could be up to 4.4C warmer depending on the emissions scenario. Fortunately, many cities are taking the matter at hand, implementing strategies to alert their residents about the risks posed by extreme heat, mitigate the potential of further warming, and adapt to the heat that can no longer be prevented.

From early warning system, emergency and heat-health action plans to architectural interventions, Earth.Org looks at how cities are keeping safe from this silent and deadly threat.

Warning: Excessive Heat!

This summer of record-breaking temperatures has seen headlines dominated by reports of millions of people under heat warnings.

Heat warning systems are essential tools designed to alert communities about impending heatwaves and extreme heat events. They are used in hundreds of cities around the world, from Las Vegas to Hong Kong, to alert and provide guidance to residents and local authorities when temperatures rise to dangerous levels. Citizens are often advised on staying cool and hydrated, seeking shelter in air-conditioned spaces, and avoid strenuous outdoor activities. Meanwhile, relevant local departments are alerted about the need to take preventive measures such as opening temporary shelters and cooling centers.

In a warming world, these warning systems are essential. But can they save lives?

While there is no straightforward answer, past events showed us that warnings alone do not compensate for the unpreparedness of societies to heat events.

In 2021, warnings were not enough to prevent hundreds of fatalities in the Pacific Northwest. 441 people died to extreme heat between June 27 and July 3. More recognized for its overcast skies and light rain, the Northwest is relatively unaccustomed to extreme heat. This translates into inadequate infrastructure and poor understanding of the risks, the combination of which can be fatal.

Similarly, the UK, a nation not traditionally associated with favorable weather, is only now beginning to experience the realities of global warming. Its national weather agency, the Met Office, issued the country’s first ever red “extreme heat” warning in July 2022, when the mercury hit 40C for the first time in recorded history. The government declared a national emergency; however, the reality is that no one was prepared.

“It was a real challenge,” said Renee Salas, an emergency medicine physician at Massachusetts General Hospital and Harvard Medical School, recalling the heatwave. “We’re used […] to gray, overcast weather, generally the average July temperature is 20C. And so there was a real difficulty in communicating to people ‘this isn’t beach weather or park weather or going-on-an-ice-cream weather’. If you’re in a group that might be vulnerable, if you’re older, if you have certain pre-existing health conditions, this is genuinely very dangerous.”

Official estimates put the number of heat-related fatalities that summer at 2,985, but there is little doubt that the death toll was much higher.

“When you go to hospital with a heat-related condition, it doesn’t go on your death certificate that you died because of a heatwave. It’s something else… a cardio-vascular event or something like that,” Salas explained.

Communication barriers and limited access to technology, particularly for vulnerable populations like the elderly, low-income households, and the homeless are some of the most apparent challenges authorities face with regards to heat warning systems. The issue is particularly pronounces in low-income countries, which lag behind in terms of connectivity. With more than 2.6 billion people – nearly 32% of the world population – still offline, such channels can only go so far.

Should We Name Heatwaves?

Aside from connectivity, another issue in effectively communicating heat risks is that people still underplay or do not fully understand them. This is particularly true, as Salas pointed out, in places like the UK, which are not accustomed to it. To enhance understanding and boost preparedness, some have suggested treating heatwaves like any other extreme weather-related event.

“Heat waves are a weather event that should be treated with the severity that other weather events are treated,” Andrew Mackenzie told Bloomberg in August. Mackenzie is Associate Director of Strategy and External Relations at the Physiological Society, one of many organizations that in recent months has appealed to metereologists to start naming heatwaves, just like they do with hurricanes and typhoons.

In 2022, the Spanish city of Seville, the warmest city in Continental Europe, put the idea to the test, naming a six-day heatwave “Zoe.” A peer-reviewed study on the effectiveness of Seville’s experiment published earlier this year concluded that around 6% of those surveyed two months after the event recalled the heatwave’s name. They also demonstrated greater understanding of the risks and were more likely to have taken steps to stay safe during the heat event and trust their government’s response, the study found.

“Everything should be on the table to save lives,” said study co-author Kathy Baughman McLeod.

Since then, however, the US National Weather Service and the United Nations’ World Meteorological Organization (WMO) have rejected the idea owing to a lack of evidence. The latter has gone as far as saying that naming heatwaves might have the opposite effect as it may interfere with existing warning protocols.

Protecting Workers

With summer heat intensifying and heat streaks becoming longer, there is an urgent need to protect those particularly at risk. One highly vulnerable group is outdoor workers, who are exposed to high temperatures for prolonged periods.

Some governments have guidelines in place for scheduling work during cooler times of the day, providing access to shaded areas, and encouraging frequent breaks to rehydrate and cool down. But more needs to be done.

Hong Kong, where summer temperatures averaging 32-35C are coupled with high levels of humidity for months on end, has rolled out heat stress systems to protect its outdoor workers. The three-tier system (Amber, Red and Black) is meant to “help employers and employees better understand the level of heat stress while working outdoors or indoors without air-conditioning systems.” Results have been mixed.

In July, a Hong Kong NGO urged the government to review its Heat Stress at Work Warning system after dozens of interviews with street cleaners and other outdoor workers revealed that 90% of them had experienced tiredness, thirst, headaches, dizziness, rises in body temperature and nausea while working, despite employers offering portable fans, clothing, and drinking water. As of July 14, when the report was released, Hong Kong had already issued the amber Heat Stress at Work warning 96 times.

Many of the interviewees who experienced heat stroke suggested the effects of prolonged exposure to extreme heat are not appropriately reflected by the warning system, which often leaves an amber warning in place for several hours. Chloe Au, a social worker for the alliance, said that red alert should be issued instead.

Hong Kong outdoor workers are not alone. In June, UK trade unions called on the government to adopt a new legal maximum temperature of 30C at work. At the time of writing, the UK has regulations in place that set a minimum temperature for indoor workplaces but no maximum temperature.

“[W]orking in sweltering conditions can be unbearable and dangerous – so spare a thought for those in overheated shops, baking offices or toiling outdoors in direct sun,” said Trades Union Congress (TUC) General Secretary Paul Nowak. “Indoor workplaces need to be kept cool, with relaxed dress codes and flexible working to make use of the coolest hours of the day. And employers must make sure outdoor workers are protected with regular breaks, lots of fluids, plenty of sunscreen and the right protective clothing.” 

Nowak said workers are “struggling to cope” and urged the government to improve the law, invest in resilience and deliver climate action as extreme heat becomes “the norm.”

You might also like: What Do Heatwaves Tell Us About Climate Change?

Reshaping Cities: A Work in Progress

Cities are starting to transform and evolve with a long-term perspective to adapt to this “new normal.”

The main issue urban areas face is the lack of green spaces. In high-density cities like Hong Kong, permeable vegetation is gradually replaced by impermeable concrete for skyscrapers and infrastructure. That concrete makes cities hotter is no secret: the modified land surface, such as dark pavement and roofing, stores more heat – a phenomenon known as the urban heat island (UHI) effect.

An analysis conducted by Climate Central of 44 major US cities, which collectively are home to 74 million people, found that about 55% of them live in census tracts that feel at least 8F (approx. 4.4C) more heat because of the local built environment. The study concluded that about 80% of the US population lives in cities where the urban heat island effect can worsen heat extremes.

Heat mitigation strategies focus on cooling urban environments through thoughtful planning and design. The most obvious approach, and repeatedly proven to be an effective one, is increasing vegetation by planting trees and enhancing green cover.

Cities like Singapore witnessed the benefits of this firsthand.

The city, a prime example of sustainable urban planning, has successfully cooled down large areas by planting over 7 million trees and creating more than 300 parks and gardens. Similarly, the city of Utrecht in the Netherlands has enhanced its green coverage by installing green roofs on more than 300 bus shelters.

While green spaces and increased shade remain the most effective ways to tackle urban heat, other interventions have shown promising results.

Los Angeles, where approximately 45% of the population is exposed to at least 8F (approx. 4.4C) more heat owing to the built environment, has been actively testing cool pavement since 2017. Cool pavements have a reflective coating that helps reflect, rather than absorb, sunlight.

A research conducted in the city in the summer 2022 revealed that during an extreme heat event, cool pavement-covered areas saw ambient air temperatures as much as 3.5F (1.9C) cooler than those in the adjacent neighborhood. On sunny days, ambient air temperatures were reduced by up to 2.1F (1.2C); at night, they were up to 0.5F (0.3C) lower. The coating also lowered surface temperatures by up to around 10F (5.6C).

Los Angeles has taken other proactive measures to protect its citizens from heat, including setting up more than 170 cooling centers – public facilities such as libraries, schools, community centres, or shelters that offer air-conditioned spaces, water, and information for people who need to escape the heat, especially those who do not have access to cooling at home. 

Cooling centers can save lives, but they do have their limitations.

“Cooling centers are fine as long as you can get there,” said Larry Kalkstein, the chief heat science adviser at Arsht-Rockefeller Foundation Resilience Center, adding that they are just a “temporary fix.”

A 2017 review on the implementation of cooling centers conducted by the US Centers for Disease Control and Prevention (CDC) concluded that their effectiveness is “unclear.” The analysis found that those who are most vulnerable to heat do not always use them. Once again, communication barriers and poor understanding are to blame.

No Right Or Wrong

Every city faces unique challenges influenced by factors such as geography, climate, infrastructure, and socio-economic conditions. For instance, densely populated areas may struggle with heat islands due to high concentrations of concrete and limited green spaces, while coastal cities might contend with elevated humidity.

Warning systems can provide real-time alerts about extreme heat events, enabling residents to take precautionary actions, while adaptation measures – such as increasing urban greenery, enhancing building materials for heat resistance, and improving public transportation – can mitigate heat impacts in the long term.

There is no one-size-fits-all solution to combat urban heat, and a combination of warning systems and tailored adaptation measures remains the most effective choice.

Research shows that cities that adopt a multifaceted approach not only reduce heat-related health risks but also enhance community resilience against future climate challenges. By integrating local data and community input, urban planners can develop strategies that are responsive to specific needs, ensuring that all residents are better protected from the adverse effects of rising temperatures.

Featured image: Kyle Lam/hongkongfp.com.

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Read part 1 of our heat series, where we looks at how extreme heat affects the human body and what socio-economic and physiological factors play a role and part 3, where we give tips on how to stay cool during a heatwave.