If it feels as if it’s getting hotter, it may have something to do with where you live.
While talk of warmer temperatures often centers on climate change and trapped greenhouse gases from fossil fuels, people who live in cities and built-up metropolitan areas also experience the urban heat island effect.
As average global temperatures continue to rise, this phenomenon makes the situation much more serious – a Climate Central study shows that 80% of Americans live in in cities, where the effect can worsen heat extremes. According to the Environmental Protection Agency, vulnerable populations (older adults, children, people of color, outdoor workers and people already in poor health) are at higher risk of deadly heat-related illnesses like heat stroke and heat exhaustion.
What is an urban heat island and how does it affect cities?
Heat islands occur when impervious surfaces such as concrete and asphalt increase the surrounding air temperatures by absorbing sunlight and retaining heat.
On warmer, sunnier days, air temperatures in an urban area can run a range of 1 to 9 degrees warmer than in rural areas just a few miles away. Even at night, temps can range 2 to 5 degrees higher as concrete and rooftops retain the heat of the day.
Air conditioning used by those who live in heat islands, which increases energy consumption and greenhouse gas emissions, compounds the effects.
Large heat islands in the US
A July 2023 Climate Central study of the urban heat island index found an estimated 41 million in Census tracts with an urban heat island index of 8 degrees or higher. The index measures how much warmer urban areas are than nearby rural census tracts. The heat maps below show how much more intense the heat is in a city’s urban core.
What can be done to relieve the effects of heat islands?
While a city’s weather and proximity to geographical features that impede cooling can’t be controlled, city planners can consider a few key tools to combat an urban area’s propensity to attract and retain heat.
Among those are more thoughtful urban development, adding green space and more efficient rooftops. Other considerations for urban planners include:
