As the Earth Gets Hotter, Can Our Cities Get Cooler?

This summer, the Northern Hemisphere has experienced record-breaking temperatures, sparking discussions about the limits of human survival. The Antarctic is also facing unprecedented changes, with sea ice failing to re-form during its winter, a drastic departure from normal patterns. These extreme heat events are not just a matter of perception; they are increasing in frequency due to climate change and are expected to worsen.

The Deadly Impact of Extreme Heat

Heat is the deadliest natural disaster most years, causing an average of 490,000 deaths globally and severe health problems for many more. According to the World Health Organization, heat-related deaths are expected to increase by 50% by 2050. However, the impact of heat on health is not distributed equally. Vulnerable populations, particularly in developing countries like South Asia, Africa, and East Asia, are at the greatest risk. These regions have contributed the least to climate change and lack the resources to adapt effectively.

Inequities Within Cities

Within cities, the poorest and most marginalized neighborhoods are often the hottest. These areas typically have less green space and more infrastructure that absorbs and retains heat, such as dark, hard surfaces. This phenomenon, known as the urban heat island effect, means that cities or parts of cities are hotter than rural areas due to the heat-retaining properties of buildings, streets, and sidewalks.

Tools to Combat Urban Heat

Despite the devastating impact of extreme heat, communities can implement various tools to mitigate heat hazards, improve urban equity, and even combat climate change. By adjusting land cover components—such as buildings, trees, streets, and built materials like concrete, asphalt, permeable pavements, paints, and coatings—cities can significantly lower their temperatures.

Case Studies: Monterrey and Mumbai


In Monterrey, Mexico, research by WRI Mexico found a strong relationship between greater vegetation cover and lower land surface temperatures. In 22 out of 27 districts, this relationship had very high statistical confidence. Temperature differences between districts ranged up to 11 degrees Celsius (20 degrees Fahrenheit), with urban areas still showing a 6-degree Celsius (11-degree Fahrenheit) range.


In Mumbai, India, where the city’s first Climate Action Plan was developed considering heat hazards, WRI India’s analysis revealed a 5.5 degrees Celsius (10 degrees Fahrenheit) difference in mean land surface temperatures between the hottest and coolest neighborhoods. Cooler, greener neighborhoods typically have wealthier residents, while hotter areas often comprise informal settlements. Approximately 37% of Mumbai households live under metal roofs, which are associated with higher heat risk and are common in low-income areas.

Cool Infrastructure Solutions

Urban infrastructure choices can create cooler neighborhoods and cities. Cool infrastructure, both natural and built, can reduce city air temperatures by 3 to 4 degrees Celsius (5 to 7 degrees Fahrenheit). Trees and vegetation cool through evapotranspiration and provide shade, while solar-reflective materials on roofs, streets, walls, and other surfaces reflect heat back into the atmosphere.

Innovative Initiatives

  1. Kochi, India: The city has launched a tree-planting campaign informed by community knowledge and geospatial data to reduce heat in vulnerable neighborhoods.
  2. Medellin, Colombia: Over 8,000 trees have been planted to create an interconnected network of green spaces, reducing the urban heat island effect by 2 degrees Celsius (3.6 degrees Fahrenheit) after three years of implementation.
  3. Ahmedabad, India: In collaboration with non-government organizations, the city has painted the roofs of 17,000 homes white to reduce heat accumulation, particularly benefiting women in slum communities.

Benefits and Implementation Challenges

Cool infrastructure provides numerous benefits, including reduced energy consumption, improved worker productivity, more equitable access to green spaces, better physical and mental health, and improved air and water quality. However, the implementation of these solutions on a large scale faces challenges, primarily due to the lack of actionable data.

From Information to Action

Efforts like the Smart Surfaces Coalition, Arsht-Rockefeller Resilience Center, Cool Cities Network, and WRI projects such as Data for Cool Cities and Cities4Forests aim to generate local data on heat risk. By providing this data to policymakers, these initiatives help inform decisions about infrastructure choices and accelerate the adoption of cool infrastructure solutions. The goal is to enable cities to adapt to extreme heat while reducing greenhouse gas emissions and preventing even hotter temperatures in the future.

By making informed infrastructure choices, cities can create cooler, more resilient urban environments, safeguarding their residents against the escalating threat of extreme heat.

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