Rx for Hot Cities: Climate Resilience Through Urban Greening and Cooling in Los Angeles

Author: Edith de Guzman, Laurence Kalkstein, David Sailor, David Eisenman, Scott Sheridan, Kimberly Kirner, Regan Maas, Kurt Shickman, David Fink, Jonathan Parfrey, Yujuan Chen

Organization: TreePeople, Los Angeles Urban Cooling Collaborative

Year: 2020

Extreme heat causes more deaths in the United States than all other weather-related causes combined. In a warming climate, health impacts are on the rise, especially in cities, which are warming at a faster rate than non-urban areas. Reducing urban heat exposure is an equity issue, as low-income communities and communities of color are more likely to live in neighborhoods with older buildings, low tree cover, more heat-retaining surfaces, and limited access to coping strategies such as air conditioning. In Los Angeles, the three groups expected to see the largest increases in mortality as L.A.’s climate heats up are the elderly, African Americans, and Latinos.

The Los Angeles Urban Cooling Collaborative (LAUCC) is a multi-disciplinary, national partnership of researchers and expert practitioners working with communities and government toward the goal of understanding and implementing urban cooling strategies. LAUCC completed a modeling study of current and projected heat in Los Angeles County to:

  • Identify geographic areas with the highest vulnerability to heat-related death;
  • Quantify at the County level, and at a more granular level, how various scenarios (or “prescriptions”) combining increases in tree cover and solar reflectance of roofs and pavements would impact heat-related mortality, temperature, humidity, and oppressive air masses that lead to more mortality;
  • Quantify the number of years that climate change-induced warming could be delayed as a result of implementing these prescriptions; and
  • Create a replicable framework that other cities or regions can adopt and improve upon.

We analyzed meteorological data for four historical summer heat waves against mortality data to determine the numbers of excess, heat-related deaths that occur due to common heat waves in Los Angeles. We then explored the effects that various land cover prescriptions would have on reducing temperature heat and heat-related deaths. We found that roughly one in four lives currently lost during heat waves could be saved, largely in low-income communities and communities of color. We also found that climate change-induced warming could be delayed approximately 25 to 60 years under business-as-usual and moderate mitigation scenarios, respectively.