- The number of cities exposed to extreme temperatures will nearly triple over the next decades. By 2050 more than 970 cities will experience average summertime temperature highs of 35˚C (95°F). Today, only 354 cities are that hot.
- The urban population exposed to these high temperatures will increase by 800 percent to reach 1.6 billion by mid-century.
- Cities in countries that are less used to dealing with extreme heat are especially vulnerable. The 2003 heatwave in Europe led to 70,000 deaths.
- Extreme heat puts pressure on essential services such as energy, transport, and health. During the 2016 heatwave India’s hospitals received twice as many patients as usual.
- Heatwaves are an economic drain. They can cut goods and service outputs by more than 20 percent in sectors such as manufacturing and construction. Global economic costs of reduced productivity due could reach 2 trillion dollars by 2030.
- Developing heat action plans and early warning systems as well as increasing blue and green infrastructure can help increase urban resilience.
The Future We Don't Want analysis shows that, unless governments take urgent steps to cut emissions, over 1.6 billion people living in close to 1000 cities face regular, extreme heatwaves in under 30 years’ time. To put this in perspective, that is equivalent to more than 40 percent of today’s total urban population.
Today, around 200 million city-dwellers in over 350 cities live with summer1 temperature highs of over 35°C (95°F). Even at this level of exposure, heatwaves are the deadliest of all climate risks. By 2050 around 970 cities will be at least this hot, with much higher exposure in Asia, Africa and North America (see Figure 1). Average high temperatures of 35°C (95°F) will mean that heatwaves will become far more intense. Today, Egypt’s capital Cairo, for example, has summertime average high temperatures of 34˚C (93˚F). There, temperatures have reached as high as 48˚C (118˚F) during heatwaves; by 2050 this will be a lot more common occurrence across the world.
Figure 1 – Urban populations at risk from heat extremes
Extreme Heat Baseline Period 1980-2005
Extreme Heat 2050s
Cities with a three month period (consecutive months) where average maximum temperatures exceed 35°C (95°F) in the baseline period (top) compared to those that are projected to experience these temperature extremes by the 2050s (bottom).
The Future We Don't Want analysis shows that Asia, and the Middle East, are already home to many cities that experience extreme temperatures. By 2050, the number of exposed cities in these regions will increase significantly with hundreds more cities at risk. The research also shows that regions that currently have few cities that deal with extreme heat, average summertime temperature highs of 35°C (95°F), will see exposure rise dramatically. Eastern China; southern, western and northern Africa; North America and parts of South America will be especially affected. Rising urban populations in these regions is partially to blame for the increased exposure; over the next 30 years 90 percent of urbanisation is expected to be concentrated in Asia and Africa alone.
A health warning for cities
Past heatwaves offer a window into the future for cities expecting temperatures to rise. Today, nearly one third of the world’s population is exposed to life-threatening heat extremes for 20 days a year or more. Events such as the 2003 heatwave in Europe, which claimed over 70,000 lives will become more frequent and severe as early as the 2040s.
People who already live in hot places will have to adapt to even longer periods of sweltering heat; while people who live in cooler cities will be exposed to levels of extreme heat to which they are unaccustomed. When adapting to climate change, cities should plan for temperatures that make it difficult and exhausting for citizens to move around outdoors, that make it impossible to work safely outdoors, and unbearable to stay indoors without air-conditioning and ventilation.
Cities with little green space are several degrees warmer than their rural surroundings as a result of the urban heat island effect. This makes urban centres more susceptible to heat extremes which can worsen air quality, cause dehydration, heat strokes, cardiovascular complications, kidney diseases, and death. The very young, the elderly, and people with pre-existing medical conditions are especially vulnerable. Heat impacts also disproportionately affect the poorest citizens who are unable to stop work during a heatwave while being more likely to work outdoors, or in poorly-ventilated factories.
In India, heatwave deaths have almost doubled over the past 20 years, leaving health services struggling to cope. During the 2016 heatwave, government hospitals received twice as many patients as usual and a record number of people were treated for heat-related illnesses such as high-grade fever, gastroenteritis, diarrhoea, and heat cramps.
Rethinking urban infrastructure
Health systems are not the only services that will be affected; cities will also have to re-think and re-build energy and transport systems. Heatwaves are already putting some cities’ energy supplies at risk. In South Korea, during a heatwave in 2013, the government had to cut air-conditioning in public buildings across Seoul, in order to stave off a country-wide power shortage. In Germany’s capital, Berlin, during a severe heatwave in 2010, temperatures reached 38˚C (100˚F), but after the air-conditioning malfunctioned on some of the city’s high-speed trains, passengers suffered temperatures of 50˚C (122˚F), forcing trains to be evacuated.
Service disruption of the sort experienced in Seoul and Berlin comes at significant economic cost and such impacts, combined with an incapacitated workforce, can cost cities billions of dollars. According to the Intergovernmental Panel on Climate Change’s most recent report, reduced labour productivity from high temperatures could reduce goods and service outputs by more than 20 percent in specific sectors such as manufacturing and construction by 2050. Another study estimates that, the economic cost of reduced productivity due to heat extremes will reach $2 trillion globally by 2030; equivalent to the GDP of India, the world’s sixth largest economy.
Responding to a hotter world
In India, where hundreds of additional cities will be exposed to extreme temperatures by 2050, the government has published a set of guidelines to help city governments prepare heat action plans. Ahmedabad was the first Indian city to develop such a policy, together with an early warning system, which issues warnings seven days before a heatwave; allowing city officials to plan their response. After the implementation of the Heat Action Plan, reports suggest that heat related deaths in the city have fallen by around 20 percent.
Spearheading this effort has been the work of the Natural Resources Defense Council (NRDC), in partnership with the Indian Institute of Public Health – Gandhinagar. Their work, supported by the Indian Meteorological Department and the National Disaster Management Authority, has helped India’s cities to better prepare for heat than ever before.
Listen, below, to Anjali Jaiswal, Senior Attorney and Director of NRDC’s India Initiative speak about their work.
A dozen other Indian cities have followed in Ahmedabad’s footsteps, and in 2018 the International Development Research Centre announced that New Delhi Municipal Council will also develop a Heat Action plan. Country-wide India’s heatwave response has achieved dramatic results “In 2015, heat related mortality was 2,600,” said Dr KJ Ramesh, Director General of India’s Meteorological Department, “with improved response systems at the local level we have brought it down in 2017 to less than 200.” Dr Ramesh, attributes the success to a range of policy measures, including directives for outdoor workers, and a comprehensive public information campaign using radio and television.
“Simply giving warnings is not enough; people also need to understand how to respond to the warnings.” Dr KJ Ramesh, Director General, India Meteorological Department
Seoul, the capital of South Korea, has also seen success with its response to extreme heat. In 1994 the city experienced temperatures of over 38˚C (100˚F) in a heatwave that claimed around 800 lives. In a response to this, South Korea’s worst ever meteorological disaster, the city rapidly expanded its green space and began issuing heatwave advisories when temperature highs reach 33˚C (91˚F) for 2 consecutive days.
“When heatwave advisories are issued, we monitor the situation closely,” said Mr. Chando Park, Manager for Disaster Response Division, “we provide emergency help to those who need it, and we make sure that workers are able to take breaks during the hottest hours of the day. We also set up and run cooling shelters where low-income people … who cannot afford air conditioning, can visit and avoid the sweltering weather.”
These measures appear to have been effective. In 2016 another heatwave hit the city, with temperatures reaching close to 37˚C (99˚F). 41 heatwave advisories were issued that year, but there were no reported fatalities in Seoul.
On the United States’ east coast, the city of Philadelphia has seen heatwaves increase from 4 to 12 days a year between 1980 and 2010. Deaths from heat stroke have risen in lockstep with the rising temperatures, averaging 620 fatalities per year in the 5 years to 2010. In response, the city government has designed a set of indicators to identify residents that are most at risk. This measure revealed that over half a million Philadelphians live in vulnerable locations. Based on this data, the Franklin Institute, has been able to provide information to community organizations on how to cope with extreme heat events.
Other heat-related policies go beyond emergency response, reducing heat stress by re-designing the built environment itself. One of the more innovative retrofitting approaches can be seen in Berlin, which has plans to become a “Stadtschwamm” or “Sponge City.” To build resilience against both extreme temperatures and flooding, Berlin developed the 2017 plan “ StEP Klima KONKRET”. The plan would see hard surfaces such as cement and asphalt on buildings, roads, and walkways, replaced with trees, grass, green roofs and urban wetlands. If implemented city-wide, these measures would keep the Berlin several degrees cooler during periods of hot weather and absorb water during heavy rains.
“After the heatwaves in the mid 1990s, Seoul launched the ‘Ten Million Tree Planting Campaign.’ By the time the project was complete in 2002, the city had planted 16 million trees and expanded its green space by 3.5 million m2. Now we have a lot of new city parks, one of which replaced an old landfill site.” - Mr. Dongjoon Ha, Deputy Director for Climate Change & Sustainability, Seoul, South Korea.
Other cities are modifying building designs and regulations to withstand urban heat. In the historically cool city of Antwerp, residents are now required to follow building codes that take resilience to heat into account. In the not-so-cool cities of Multan in Pakistan and Surat in India, new, low-cost, passive-cooling designs are being tested to help the urban poor deal with heat extremes. These measures have a huge impact on household finances. In Multan, for example, households currently spend half of their income on measures to reduce heat stress and pay for health care arising from heat exposure.
Most interventions for tackling extreme heat target the formal built environment, however. This often means that the most vulnerable urban residents, living in informal settlements, are left unprotected. The problem is especially prevalent in developing country cities, where informal settlements comprise between 20 and 80 percent of the population. By 2020, the number of people living in informal neighbourhoods is expected to reach nearly 900 million globally, which poses a considerable challenge for city governments trying to tackle the impacts of extreme heat.
Efforts to address extreme heat for those living in informal settlements are already underway in India. The Mahila Housing Sewa Trust, an NGO led by the Self-Employed Women’s Association, has installed water-proof modular roofs in slums in several cities, including Delhi. The roofs, made of paper waste and coconut husk, are cheap and easily installed and have been shown to bring down temperature by as much as 6˚C (11˚F). “The roofs are installed in very poor neighbourhoods,” said Ganesh Gorti, Research Associate at India’s Energy and Resources Institute, “they are designed to target people who do not have access active cooling and typically live in houses with sheet metal roofs that get very hot in summertime.”
Whether in Seoul, Berlin or Delhi, any city’s heat action strategy will have to take account of socio-economic factors in order to strengthen resilience to future heat extremes. In a warming world, and especially under a business-as-usual climate scenario where the goals of Paris Agreement are not met, it is critical that adaptation strategies are supported by wider efforts to improve urban infrastructure and services. A resilient city needs accessible and affordable healthcare, reliable public transport, uninterrupted electricity supplies, clean drinking water and well-functioning sanitation systems. Cities around the world must work together to make sure that The Future We Don't Want heat scenarios are not realised, while simultaneously planning for the possibility that they are.