As the planet warms, there is an increasingly urgent need for strategies to prevent the heat-health impacts of climate change. Cooling urban neighborhoods by adding trees and vegetation and increasing solar reflectance (or albedo) of roofs, pavements, and walls can mitigate urban heat — a problem that disproportionately affects low-income communities and people of color. In this follow-on study, we focused on heat-related morbidity as measured by emergency room visits. Using synoptic climatology, we used meteorological data for historical summer heat waves, classifying days into discrete air mass types. We analyzed those data against historical data on ER visits to determine excess and heat-related morbidity. We then used the Weather Research and Forecasting model to explore the effects that tree cover and albedo scenarios would have, correlating the resultant meteorological data with standardized morbidity data algorithms to quantify potential reductions in ER visits. We tested “prescriptions” of low, medium, and high tree cover and albedo changes and found that all-cause and heat-related ER visits would be reduced substantially — especially during moderate heat waves and during hot, dry Santa Ana heat events. ER reductions in the double-digit percentages were common, meaning that between 25% and 50% of ER visits could be avoided if L.A.’s urban environment had more trees and higher-albedo surfaces.

Eisenman, David
Kalkstein, Laurence S.
Parfrey, Jonathan
Chen, Yujuan
Koetter, Maria
Herrmann, Dustin L.