Bogota, Colombia / Credit: Devasahayam Chandra Dhas
Major new reports detail how rising temperatures will see cities exposed to more intense heat waves and widespread disease risks
The world's fast-expanding urban population is facing a future of escalating climate risks that are set to result in severe health and economic impacts.
That is the conclusion of a new report from the World Resources Institute's (WRI) Ross Center for Sustainable Cities, which assesses the climate hazards almost 1,000 of the world's largest cities can expect to face under a 3C warming scenario based on current emissions trajectories and under a 1.5C warming scenario where global net zero goals are met.
It warns that if temperature goals are missed cities across the globe are set to endure far more frequent and longer heatwaves, skyrocketing demand for cooling, and more widespread disease risk, with low-income cities in sub-Saharan Africa, Latin America, and Southeast Asia likely to be hardest hit.
WRI analysed climate hazards for 996 of the world's largest cities - which are together home to 2.1 billion people - using estimates based on downscaled global climate models.
The results reveal a significant difference in climate impacts under a 1.5C and 3C scenario, and provide city governments with granular data and modelling on the impacts they can expect to see in the coming decades.
"The difference between 1.5C and 3C has life or death consequences for billions of people worldwide," said Rogier van den Berg, global director at the WRI Ross Center for Sustainable Cities. "This data should serve as a wakeup call to every city and national government leader: now is the time to start preparing cities for a much hotter world, while doing everything we can to slash emissions."
The report detailed how at 3C of warming most large cities can expect both longer and more frequent heatwaves, leading to impacts on public health, labour capacity, and productivity.
Under a 1.5C scenario, the longest heatwave each year would be expected to last an average of 16.3 days, with three per cent of the world's largest cities experiencing heat waves lasting one month or longer annually. However, under 3C of warming, the average duration of the longest heat wave could jump to 24.5 days, with more than 16 per cent of cities exposed to at least one heat wave lasting a month or longer every year.
The report highlights how extreme heat would significantly increase the demand for cooling and energy, calculating that under 3C of warming 194 million people in cities would potentially see their cooling demand double from historic levels.
The modelling also details how higher temperatures would create more optimal environments for mosquitos that carry arboviruses, such as dengue, Zika, West Nile, yellow fever, and chikungunya. A 3C warming scenario would see an average of six more days of peak arbovirus-transmission conditions each year compared to a 1.5C scenario.
"Climate change has profoundly unequal impacts both across cities and within cities," said Anjali Mahendra, director of global research at the WRI Ross Center. "Cities in low-income countries are often more afflicted and have fewer resources to cope, which means we need to drastically increase financing for adaptation and find ways to direct it to the hardest hit cities and communities. Even within a well-resourced city, the most vulnerable populations will be disproportionately affected."
Antha Williams, who leads the Bloomberg Philanthropies' Environment program, which funded the latest research, said the results "make it clear that we can't afford to delay action on climate change any longer as dire consequences await cities in a 3C world".
"Now it's more important than ever for national and local governments to come together to accelerate progress and protect the millions of lives in urban communities from the threatening impacts of climate change," she added.
The report came just a day after a separate analysis from the C40 group of mayors and the Mayors Migration Council, which detailed how climate change impacts are also set to accelerate flows of rural to urban migration, further ratcheting up pressure on city infrastructure.
Cities are already home to more than half the world's population and the share of the global population living in urban centres is predicted to rise to two thirds by 2050, with over 90 per cent of urban growth coming in lower income countries.
The new report studies 10 developing economy cities across three continents, including Bogotá in Colombia, Amman in Jordan, Freetown in Sierra Leone, and Karachi in Pakistan. It calculates that the 10 cities can expect to receive eight million people by 2050 as a direct result of climate change, exacerbating existing trends of migration towards cities.
The study found that in every country, multiple, overlapping climate factors, such as reduced crop yields, rising sea levels, and extreme weather, were expected to result in increased levels of migration. The modelling suggests Karachi could receive as many as 2.3 million domestic climate migrants by 2050, while cities like Bogotá and Rio de Janeiro could see a three-fold increase in the number of climate migrants compared to scenarios where the global climate goals set under the Paris Agreement are met.
Vittoria Zanuso, executive director of the Mayors Migration Council, urged city governments to start preparing now for increasing numbers of climate migrants.
"The World Bank projects climate change could displace over 200 million people by 2050, with most relocating within their own countries, often from rural to urban areas," she said. "Africa alone could see 85 million internal climate migrants. But while climate change is a crisis, the migration it causes doesn't have to be.
"If managed effectively, it can help build stronger cities and benefit other marginalised communities. We've seen city leaders drive inclusive climate action through the Global Cities Fund for Migrants and Refugees - whether supporting green microenterprises in Freetown or integrating migrant waste workers into cooperatives in Accra. Today's research with C40 Cities adds to this growing body of evidence, showing the potential of city leadership to turn climate migration from a crisis into an opportunity."
You can now sign up to attend the fifth annual Net Zero Festival, which will be hosted by BusinessGreen on October 22-23 at the Business Design Centre in London.
