As extreme heat grips the globe, access to air conditioning is an urgent public health issue

Cities around the world are running out of steam The heat of summer. Last week, the UK, known for its cool and rainy climate, exceeded its record temperature registration, peaking at 104.4 degrees Fahrenheit. Meanwhile, American cities are scrambling to protect their residents and physical infrastructure from the dangers of extreme heatwhich can lead to schooling closurespublic transport system malfunctionstense electrical networks, and more. Extreme heat kills 600 people in the United States each year; the elderly, very young children and people with chronic illnesses are the the most vulnerable.

Climate change is exacerbating these trends. At the end of the century, realistic scenarios predict that the planet will warm by 5 to 6 degrees. Urban areas are particularly affected, as large residential and commercial buildings, roads, sidewalks and other impervious surfaces throughout the built environment create heat islands which absorb and retain heat during the hottest hours of the day and reduce cooling during the night. According to these projections, in the face of a once-in-a-generation heat wave, more than 20,000 lives could be lost in major US cities.

Erenough interior air conditioner, the United States is much better equipped to keep people safe during periods of extreme heat than it was a century ago. Nationally, about 70% of homes now have central air conditioning, while about 10% of households have no air conditioning. But the presence and type of home air conditioner varies greatly by geography. Like exposure to other climate hazards, protection from extreme heat also varies by income, occupation, and race.

Metropolitan areas vary widely in the prevalence of home air conditioning

Access to home air conditioning varies across the United States, largely, but not entirely, reflecting regional differences in climate. In Southeast and Southwest metropolitan areas such as Atlanta, Houston, and Phoenix, 95% of homes are at least partially cooled by central air, while less than 3% have no air conditioning. (The Census Bureau’s U.S. Housing Survey asks households if any part of the house has air conditioning.) West Coast metropolitan areas such as Seattle, San Francisco, and San Jose, Calif., have the highest share. the highest number of homes without air conditioning, while Northeast and Midwest metropolitan areas with older housing stock tend to have more homes that rely on window air conditioning units.

Regional patterns reflect differences in both climate and age of the housing stock. The Pacific Northwest, West Coast and Great Lakes metropolitan areas have historically had mild summers, with less need for home cooling, patterns that may not last under the stress of climate change. Last year, almost 70 people in Portland, Oregon. died in a heat wave.

Additionally, some metropolitan areas close to each other—sharing broadly similar climates—have pronounced differences in access to AC power. In Ohio, Cincinnati and Cleveland have similar summer climates, but three times as many households in Cleveland — a significantly poorer metro area — lack air conditioning. In California, Riverside and Los Angeles offer an unusual comparison of geographically close metropolitan areas: approximately 20% of households in Los Angeles (which enjoys cooler temperatures due to its proximity to the ocean) have no air conditioning, compared to less than 7% of households in Riverside, warmer. (also known as the Inland Empire).

In all metropolitan areas, low-income households and renters are less likely to have AC

Pooling data from the 35 metropolitan areas we observed shows that access to air conditioning, particularly central air, is positively correlated with household income (Figure 2). About 12% of households in the lowest income quartile have no air conditioning and just over 60% have central air. In the highest income quartile, only 6% have no air conditioning and over 80% have central air. (Income quartiles are defined in metropolitan areas, taking into account that income levels and the prevalence of AC vary widely from place to place.)

Lack of AC power is more prevalent among low-income households

These differences are also reflected in tenure status. More than 12% of renter households – who typically have lower incomes and wealth than owners – have no air conditioning, and less than 60% have central air. In contrast, less than 7% of homeowners have no air conditioning and almost 80% have central air.

Renters have less access to air conditioning – especially central air conditioning – than owners

Like exposure to other climate risks, access to air conditioning shows a pronounced racial equity gap

In metropolitan areas where a significant number of homes do not have air conditioning, there are pronounced racial gaps, with black and Latino or Hispanic households less likely to have air conditioning. The built environment in many historically black neighborhoods— lack of tree cover and more paved surfaces — compounds the problem.

New York and Detroit have relatively large black populations and large disparities between blacks and whites in access to AC power. In Detroit, less than 4% of white households have no access to AC power, compared to more than 15% of black households. New York’s black-to-white AC access gap is also large, at just under 10%.

Rochester, NY and Seattle have larger white majorities, but equally large disparities: less than 15% of white households in Rochester have no air conditioning, compared to nearly 30% of black households. Black, Latino or Hispanic and Asian American households in Seattle are all less likely to have AC. In addition, minority households are more likely to live in the hottest part metropolitan areas, increasing their risk of extreme heat.

Black and Latino or Hispanic households are more likely to lack air conditioning

Lack of air conditioning is especially a problem for older homes

Home air conditioning, particularly central air conditioning, is a relatively recent feature of home construction and did not become widespread until the mid-twentieth century. Indeed, the adoption of modern air conditioning enabled the rapid growth after World War II of Sun Belt Metropolitan Areaswhere most homes are new and central air conditioning is standard.

Among the Northeast and Midwest metro areas, where prewar homes make up a much larger share of the housing stock, central air conditioning is fairly common in newer homes, while window units have been added to many older homes. For example, 95% of homes in Detroit after 1990 and 77% of homes in Rochester after 1990 were built with central air conditioning, compared to less than 40% and 20% of pre-1940 homes in those locations, respectively. The Pacific Northwest, known for its mild summers, is one region where air conditioning has not become the norm in new construction; less than half of Seattle homes built after 1990 have some form of air conditioning, and less than a third have central air.

Older homes are less likely to have air conditioning, especially central air conditioning

Policy makers need short-term and long-term strategies to reduce the impacts of extreme heat

As climate change makes extreme heat events more frequent in the United States, policymakers should consider a range of adaptation and mitigation strategies to protect public health and safety. Short-term options include distributing high-efficiency air conditioning units to homeowners and landlords, especially those with older properties. Many low-income households are already facing lodging and energy cost burdens and cannot afford the additional electricity costs associated with AC, so increased utility subsidies may need to be increased (at least during heat waves). Local governments should also increase the number of cooling centers (often held in schools, libraries, churches, and other anchor institutions), especially in low-income, black, Latino, or Hispanic communities where access to AC power is limited.

Longer-term options include increasing subsidies and technical assistance for landowners, whether landlords or owners, to weather their buildings. Local and state governments should also prepare for a warmer future by reduce the effects of urban heat islands. Strategies such as to plant treesfor now parksbuilding fountains and mistsfunding green or cool roofsand installation lighter colored pavement are relatively quick and inexpensive, unlike long-term goals such as more climate-friendly land use.

Any policymakers complaining about public investments to build more heat-resistant communities should consider the benefits: reduced spending on paramedics and hospitals called in to treat heat-related illnessesnot to mention saving human lives.

About Christopher Easley

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