Analysis for Tacoma, Washington | 2020
In Tacoma, our analysis found that urban heat islands increase maximum temperatures by as much as 6.2 degrees F above the local baseline. Combined with regional climatic effects, neighborhoods in Central and South Tacoma may be as much as 14 degrees F hotter than neighborhoods in North Tacoma. 11,980 people live in neighborhoods where maximum temperature exceed the 90th percentile and where average per capita incomes are less than 200% the federal poverty level (outlined in black in map). Every additional degree carries significant public health costs.
In Tacoma’s most severe urban heat islands, all-cause mortality rates are estimated to increase by as much as 8.4% when regional temperatures exceed 82 degrees F. Tacoma experiences about 30 days above 82 degrees per year, on average. Our model estimates that 3– 15 lives are lost in the city each year due to extreme heat exacerbated by urban heat islands.
The public health burden of urban heat islands is disproportionately levied on the lowest income households. In Tacoma there is a strong correlation between household income and urban heat islands.
Without intervention, Tacoma’s heat island impacts will grow significantly in a changing climate. Number of days above the 82 degree F threshold has increased by more than 50% since 1980. On the current trajectory the Seattle-Tacoma area will experience 42 days above the temperature threshold by 2050, and 59 days above the threshold by 2100.
“There is a strong correlation between summer heat and negative health outcomes. Temperatures above 82°F significantly increase the risk of cardiovascular diseases, respiratory illnesses, and heat stroke.”
*High Risk Area (outlined in black) is defined as neighborhoods where the urban heat islands increase temperatures by 2°F or more and where average per capita incomes are less than 200% the federal poverty level.
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Photo Credit: Micah Sheldon via Flickr
Wildish, J. 2020. Urban Heat Island Analysis: Tacoma, Washington. Earth Economics. Tacoma, WA.
References
Anderson, B. G., & Bell, M. L. (2009). Weather-related mortality: how heat, cold, and heat waves affect mortality in the United States. Epidemiology (Cambridge, Mass.), 20(2), 205.