The World Health Organization (WHO) estimates that extreme heat kills almost half a million people each year—more than war, terrorism and malnutrition combined. That number is likely to rise as the climate becomes hotter and less predictable.
But the threats to public health posed by climate change go well beyond extreme heat. Historic rainfall and rising temperatures are driving malaria, cholera and dengue outbreaks, and expanding these diseases into new regions. Meanwhile, air pollution from wildfires has been linked to everything from cancer to heart disease.
These effects will be felt most acutely by city-dwellers, where concrete absorbs and re-emits heat, and higher population densities allow pathogens to spread more easily. Despite nearly 70% of city leaders recognizing climate-related health threats, and more than 90% reporting economic losses from such events, less than a third of cities have a resilience plan that integrates climate and health, according to a new report produced by the Rockefeller Foundation, shared exclusively with TIME.
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With the support of the Rockefeller Foundation, the Urban Pulse Initiative surveyed 191 city and civil society leaders from 118 cities across 52 countries,as part of a collaboration between Yale University and the Resilient Cities Network.
“While [cities] are particularly vulnerable, they’re also woefully underprepared for what is coming,” says Naveen Rao, senior vice president of the Rockefeller Foundation’s Health Initiative, which led the report’s development in partnership with thinktank Global Nation. The Foundation is committing $1 million to the C40 Cities Climate Leadership Group, a global network of nearly 100 mayors, to support the implementation of the three-pronged climate and health strategy it outlines in the report.
The report highlights individual cities using innovative approaches to minimize climate-driven health risks. These isolated success stories could show a path forward for other cities facing what the report calls a “climate-health crisis.”
“The first prong [of the strategy] is to collaborate the climate/meteorological data with the health data,” Rao says. “There are other agencies that live and die by meteorological data,” explains Rao, citing aviation and agriculture. And while the WHO and the World Meteorological Organization (WMO) have collaborated closely for roughly a decade, integration at the local level is rare.
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One city making strides in this area is Rio de Janeiro. By integrating health and meteorological data, Rio developed an early warning system for dengue fever, a mosquito-borne viral disease, nicknamed “bone-break fever” for its debilitating aches.
During Rio’s winter, when weather is generally cooler and dryer, dengue cases drop. But in 2023—one of Rio’s mildest winters ever—cases of dengue remained unseasonably high. That September, the city’s Epidemiological Intelligence Center, a team established in 2022 with meteorological support from the city’s municipal government, alerted health authorities that the impendending wet season could create ideal conditions for an outbreak.
“We were able to see where the number of cases was growing, where they were concentrated,” says Gislani Mateus, who is superintendent of health surveillance at Rio’s municipal health department. The epidemiological modeling, which used weather data, case numbers, and mosquito-population data from a network of over 2,500 traps, was used “to direct efforts to control both mosquitoes, and healthcare,” Mateus says. The strategy would evolve into the Dengue Emergency Operations Center last February, when the city declared a dengue epidemic.
Though the team didn’t avert the epidemic, their models predicted a spike in dengue cases two months earlier than forecasted by traditional epidemiological models. Consequently, Rio fared better than other cities in Brazil’s southeast, and recorded its lowest ever death rate from a dengue epidemic. Mateus says they are now working with Brazil’s national health ministry to implement the strategy elsewhere.
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Another city using predictive modeling against dengue is Bangalore, India, where a team used climate and health data to make AI-driven outbreak forecasts at the district level. But the vast majority, 77% of cities, do not use meteorological data in health surveillance systems, and replicating Rio’s success requires more than predictive modeling.
“With climate change, it’s increasingly important that we have this union between weather and health in our epidemiological analysis,” Mateus says. “But it’s also critical we have public health services with sufficient numbers to attend to the population.”
The report outlines a second crucial prong to city preparedness: ensuring experts in areas such as climate change, health, urban planning, and transport are coordinating proactively before disaster strikes. “A smoke alarm going off makes no sense without a fire engine,” Rao says. Without this collaboration, even the best forecasts will not translate into timely, effective public health interventions.
Another city the report identifies as turning warnings into action is Dhaka, Bangladesh. In 2022, the Bangladesh Red Crescent Society (BDRCS) partnered with other organizations and government agencies to implement a data-driven early action protocol to respond to heatwaves. The protocol sets clear trigger points based on temperature thresholds.
The plan was approved by the International Federation of the Red Cross and Red Crescent Societies, giving the BDRCS access to pre-arranged funding to support rapid response efforts when those thresholds were crossed, says Shahjahan Saju, who is assistant director and project coordinator of the BDRCS’s forecast based financing initiative.
In April, Dhaka was hit with its longest heatwave in recorded history. But temperature forecasting meant the city was prepared to respond before temperatures reached their peak, with efforts such as distributing 3,500 umbrellas, providing water to 30,000 recipients, and offering respite from the heat to 15,000 people through three dedicated cooling stations, Saju says. The WHO and WMO estimate that scaling a warning system like this could avert almost 100,000 deaths a year.
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Early warning systems are a case of “low hanging fruit,” says Celeste Saulo, secretary-general of the WMO, noting that many cities already collect the necessary health and weather information.
“It’s about linking those different sources of information in a way that you can put an early warning in place,” she says.
While Dhaka and Rio show how effective early action can be, a key question remains: How do you get millions of urban residents to heed public health advice? Enter the third prong of the report’s strategy: effective communication. The city of Lusaka, Zambia’s sprawling capital, found innovative ways to cut through the noise and deliver life-saving information and services when it mattered most.
In October, the Zambia National Public Health Institute reported an outbreak of cholera in Lusaka, which has been battered by both flooding and drought. By January, the casualty rate had hit 4%, four times the WHO’s threshold. Rachel James, interagency risk communication and community engagement coordinator for the Collective Service, a partnership between IFRC, UNICEF, and the WHO, recalls trudging through the streets in knee-high water. “That’s when it becomes very real.”
The high death rate was, in part, due to inaccurate risk perceptions, misinformation, and barriers to accessing health services. “To better understand what the community perceptions were,” the Collective Service visited communities, “talking to people who had survived cholera, talking to the families of people who died, and just people in the districts where there are a lot of cases,” James says. That information was shared with Zambia’s health ministry and partners to inform how they communicated, contributing to a 100% uptake of cholera vaccines, she adds.
Community engagement also revealed the barriers preventing people from accessing healthcare, such as lack of transport. In response, Zambia’s ministry of health and UNICEF jointly funded seven ambulances. Collection points were also established to provide oral rehydration solutions to those who did not require transport to a healthcare facility, James says.
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Rather than waiting until the midst of an emergency, the Rockefeller Foundation report underscores the importance of developing “always-on” communication strategies. “It was because of our work that we were already doing with the Rockefeller Foundation in-country that we were able to respond immediately,” says Maureen Mckenna, who is global coordinator for the Collective Service. “We were already working in Zambia, setting up risk communication and community engagement mechanisms to be able to respond immediately to health emergencies.”
Beyond providing a framework for city leaders and policymakers, the report says interventions that improve the resilience of healthcare systems to climate change carry “immense economic benefits.” Early estimates by research and data analytics consultancy Mathematica, commissioned by the Rockefeller Foundation, found that targeted heatwave prep in Dhaka could yield health benefits nearly seven times the cost in terms of lives saved. Yet less than 5% of climate financing goes towards adaptation, according to the Climate Policy Initiative. Rao says only a fraction of that goes to health-focused initiatives.
“We need to stay focused on mitigation, because we can’t adapt our way out of this problem,” Rao says, noting that those “that have done the least to cause this problem, climate change, are suffering the most.”
Last December, at COP28, governments and other stakeholders committed $1 billion to the climate-health crisis, including $100 million from the Rockefeller Foundation, at the conference’s first ever Health Day. But that is well short of the $11 billion each year Rao says is needed for low- and middle-income countries to adapt to climate and health impacts. “What needs to hold this whole thing together is more funding.”