As a result of human-induced climate change, areas throughout the world are experiencing longer and more intense heat waves. A “heatwave” is when the ambient temperature reaches a certain threshold for two or more days.
Heatwaves affect many areas of the world, but they are most dangerous in places where the people and infrastructure are not accustomed to or prepared for them. In parts of Europe, for example, intense heat waves in 2022 drastically affected individuals, businesses, and society. European countries are particularly vulnerable because buildings and homes often lack cooling technology, the population is generally older and thus more susceptible to heat-related illness, and crops grown in the region have difficulty withstanding such high temperatures.
Increased heat and humidity don’t affect all people equally. Older people, pregnant people, and children are more susceptible to heat-related illnesses because of their physiology. These groups have higher sweating thresholds, making it more difficult for their bodies to cool down quickly. People with chronic conditions, those who work outside, and athletes are also more susceptible. Living environment and socioeconomic status play a role in vulnerability. Poorer people, minorities, and people living in urban areas are disproportionately affected by hotter temperatures.
For those living in cities, much is this discrepancy can be due to the “urban heat island” effect, which describes how cities trap heat. This is because heat-diffusing vegetation like trees, bushes, and grasses have been replaced with pavement and buildings, which absorb and retain heat. City density can also contribute to this effect. Heat does not dissipate easily from large, closely packed buildings, and narrow streets don’t allow cooling wind to blow through. In addition, human activities like vehicles, air conditioners, and industrial sites all generate additional heat.
When urban heat islands occur in countries with widespread air-conditioning use, like in the US, energy demand spikes. This can overload systems and result in blackouts or brownouts. This high energy use also increases emissions of greenhouse gases.
Studies have found that low-income and minority populations are most affected by extreme heat. In the US, poorer and minority communities are, on average, 7 degrees (F) hotter than more affluent, whiter areas. One study found that when looking at neighborhoods by race, 71% of counties with high minority populations were hotter than counties populated by a white majority. There are associations between minority status and socioeconomic status, and many urban areas have large minority populations.
Some of this can be attributed to living conditions. Lower-income people may live in small quarters or substandard housing and may not be able to afford air conditioners and the electricity they require. They may also not have access to alternative shelter during heatwaves. Low-income neighborhoods tend to have fewer trees and less vegetation that can provide shade and soak up humidity. In addition, because of socioeconomic, environmental, and healthcare access issues, poorer people are more likely to have a greater number of chronic health problems, which puts them at a higher risk of heat-related morbidity and mortality.
Fortunately, there are strategies to mitigate urban heat islands and protect vulnerable communities that may not have the resources to stay safe during heat waves. On an environmental level, planting more trees and planning for increased urban green space can provide shade and absorb humidity. In 2007, New York City launched a “One Million Trees” initiative that planted a million extra trees within the city boroughs. Because of the success of the first initiative, the city has decided to plant another million trees in the next decade. Planners noticed that poorer neighborhoods had less tree density and noted that African American New Yorkers die from heat-related illness at twice the rate of white New Yorkers.
Different city planning and building methods can also alleviate the urban heat island effect. “Green roofs,” in which a layer of vegetation is planted on rooftops, can provide shade and absorb heat through evapotranspiration. “Cool roofs” are a strategy that uses reflective materials on rooftops to lower temperatures inside the building and reduce energy usage. “Cool Pavements” offer similar benefits by reflecting solar energy and encouraging water evaporation.
Additionally, heatwaves can often be predicted in advance, meaning that health officials can give appropriate notice to vulnerable populations and encourage them to relocate to cooling centers or places like malls and public libraries, which are often air-conditioned. Governments must also provide extensive education on reducing risks of heat illness and death, like staying hydrated, wearing breathable clothing, and checking on older family members and neighbors during heat waves. Cooling centers should be widely available and advertised in all communities.
Unfortunately, extreme heat, like all effects of climate change, will be most devastating for vulnerable people, which include older, low-income, and minority communities. We must take steps to educate people about risks and advocate for changes in planning and infrastructure that will protect against these inevitable challenges.