The workshop’s second session focused on projected increases in average and extreme temperatures, urban heat island effects and associated heat mitigation and adaptation strategies, and the public health impacts of a warming climate. The inland deserts, central valley, and many urban areas in California already experience extreme heat, and vulnerable communities that have greater exposure or lack access to air conditioning face disproportionate impacts. Guido Franco (California Energy Commission) moderated the session, calling attention to the immense scale of potential economic damages associated with excess heat-related mortality due to climate change. George Ban-Weiss (University of Southern California) shared neighborhood-scale measurements of urban heat islands and the cooling benefits associated with cool roofs and other heat mitigation strategies. Nik Steinberg (Four Twenty Seven Climate Solutions) presented a decision support tool for California public health practitioners that combines downscaled climate projections with medical records data and indicators of vulnerability. Nancy Sutley (Los Angeles Department of Water and Power) shared the department’s climate change and heat mitigation efforts and ended by identifying several priorities for future research. Elizabeth Rhoades (Los Angeles County Department of Public Health) encouraged policy makers and practitioners to frame climate change as a public health challenge as opposed to purely environmental, and she identified several open research questions from a public health practitioner’s perspective.
MODERATOR: GUIDO FRANCO, CALIFORNIA ENERGY COMMISSION
Guido Franco introduced the session on heat, susceptible communities, and public health by reviewing studies showing that use of air conditioning can significantly reduce mortality and morbidity across the state (Ostro et al., 2011; Guirguis et al., 2018). Thus, one adaptation strategy will be to increase penetration of air conditioning units, which will impact the electricity industry. Without adaptation measures, projected excess losses of life are in the thousands by midcentury (Ostro et al., 2011), and California’s Fourth Climate Change Assessment (State of California, 2018) quantifies the economic cost of this excess mortality in the billions of dollars (Bedsworth et al., 2018). Moving to the topic of heat islands, Franco explained that there are different methods to model and understand urban heat islands—for example, complex dynamic models or satellite data—but these have numerous limitations. Another challenge in adapting and responding to heat impacts is that current warning systems do not accurately represent California and are not based on strong epidemiological evidence, he said. The Fourth Assessment contained research to address both of these limitations—specifically, the installation of a dense network of sensors and monitors in Los Angeles to develop the first neighborhood scale measurements on heat island effects
and the development of a public health decision support tool based on public health data that is just beginning to be used in practice.
GEORGE BAN-WEISS, UNIVERSITY OF SOUTHERN CALIFORNIA
Ban-Weiss described the heat island effect—the tendency for cities to be warmer than their surrounding rural environments by several degrees, often in the afternoon and evening—caused by the relative abundance of dark surfaces that absorb and store heat, waste heat from human activities, and a lack of vegetation. There are several heat mitigation strategies that reduce impacts of heat islands, including cool roofs and pavements as well as street and roof vegetation or reductions in anthropogenic heat emissions. He described research contributions to the Fourth Assessment (Taha et al., 2018a) that combine models and observational data to help inform selection and investment in these strategies to mitigate heat islands in the Los Angeles area. To gather data, Ban-Weiss and his colleagues developed a mobile sensor and drove it on carefully designed routes and installed new weather stations on sites owned by Los Angeles Unified School District. They combined data from these sources with existing weather stations (both government owned and lower reliability volunteer owned and operated) to provide the first observational evidence that cool roof deployment is associated with cooling at the neighborhood scale (Taha et al., 2018b). The research was featured in a Los Angeles Times article describing the role of scientific research in informing the city’s policy goals of reducing the urban heat island effect by 3°F or more (Netburn, 2017).
Ban-Weiss went on to describe external contributions to the Fourth Assessment (Ban-Weiss, 2018; Vahmani et al., 2016; Vahmani and Ban-Weiss, 2016) that explored the potential for cool roofs to mitigate heat impacts across Los Angeles. Using aerial and satellite imagery, Ban-Weiss and colleagues showed that currently most roofs have low reflectivity and there is significant room for improvement, and that the majority of roof space in the area is residential as opposed to commercial buildings. This finding informed cool roof policies to target the residential segment of the building stock, which are being implemented through a city ordinance.1 Using the Weather Research and Forecasting Model2 parameterized for urban Los Angeles, they showed that a hypothetical city-wide deployment of cool roofs could lead to 1–2°F cooling in the afternoon. However, even if cool roofs are deployed widely, warming projected by the end of the century exceeds the reductions from this climate adaptation strategy, and thus stabilizing local temperatures will require reductions in greenhouse gas emissions. Ban-Weiss concluded by emphasizing the importance of taking a systems perspective in developing adaptation strategies—for example, considering that solutions with climate benefits may have synergistic or adverse impacts on air quality and thus human health.
NIK STEINBERG, FOUR TWENTY SEVEN CLIMATE SOLUTIONS
Steinberg began by describing the public health impacts arising from heat waves in California today and how extreme heat is projected to change over the next century due to climate change. Heat waves and heat health events—those that result in some significant public health impact—are projected to grow more severe, last longer, and occur later in the year than previously in the state, with particularly notable changes in nighttime temperatures that are of concern for vulnerable communities without access to air conditioning (Figure 3.1).
Of all extreme weather, heat is responsible for the most lives lost, explained Steinberg, sharing the example of the 2006 heat wave in California that contributed to more than 16,000 hospital visits and approximately 650 deaths (Knowlton et al., 2011). These events are projected to become more frequent over the next century; however, there are historical inadequacies (e.g., the National Weather Service issued only six alerts over the years 2000 to 2009 despite evidence showing up to 19 heat health events) (Guirguis et al., 2014), and known barriers to adaptation to extreme heat and the effectiveness of interventions varies significantly by location, demographic characteristics, and the resources available to local officials.
1 See City of Los Angeles, Ordinance No. 183149, effective August 20, 2014, https://www.ladbs.org/docs/default-source/publications/ordinances/cool-roof-ordinance-183149.pdf?sfvrsn=11.
2 See National Center for Atmospheric Research, Mesoscale and Microscale Meteorology Laboratory, “Weather and Forecasting Model,” https://www.mmm.ucar.edu/weather-research-and-forecasting-model.
Steinberg and his team conducted a survey of more than 110 public health officials across 43 counties serving in a variety of roles to ask them how improved climate and weather information could more effectively be incorporated into public health decision making. The results showed that many different organizations are involved in the complex processes of planning for and responding to heat events in both the short and long term (Steinberg et al., 2018). They found several gaps in current knowledge—for example, the need for thresholds and heat wave characteristics to help planners and designers. The team elicited practitioners’ assessments of information needs showing that information on the impacted population’s medical and occupational conditions was perceived as most valuable. Informed by this survey, they undertook development of a decision support tool to (1) integrate medical data and historical weather data to develop informed thresholds for different subpopulations and geographies at the scale of census tracts; (2) overlay probabilistic climate projections on top of these thresholds to explore frequency, duration, and severity of future heat events; and (3) explore the vulnerability of different communities to evaluate the equity implications of extreme heat. Steinberg and his team found that the appropriate threshold for susceptible communities may be 6–8°F lower than for the general population. He noted that some low-income urban areas as well as agricultural areas with fairly large numbers of outdoor workers are projected to have significantly large changes. The California Heat Assessment Tool provides projected changes in severity, frequency, and duration at the census tract scale alongside vulnerability indicators to help planners prioritize investments, and the tool is available freely online.3
NANCY SUTLEY, LOS ANGELES DEPARTMENT OF WATER AND POWER
The Los Angeles Department of Water and Power (LADWP) is the nation’s largest municipal utility, with more than 4 million customers and an infrastructure footprint that spans much of the western United States, Sutley began, so the challenge of planning for and maintaining reliable service through climate change is critical to the organization. As part of California’s long-standing efforts to mitigate and adapt to climate change, LADWP—once one of the largest emitters in the state—has reduced its greenhouse gas emissions by more than 40 percent relative to 1990 and will play a central role in Los Angeles. Mayor Eric Garcetti’s pledge to make the city carbon neutral by 2050. Sutley explained that LADWP is also pursuing adaptation efforts for risks including sea level rise, hydrological changes and prolonged drought, increased wildfires, and extreme heat in their service territory, which is largely highly urban and paved and has many vulnerable communities. Heat is also impacting LADWP operations through increased peak power demand and damage to distribution equipment that is unable to properly
cool down with high nighttime temperatures, and the utility planning needs to consider projections for fourfold increased frequency of extreme heat events, said Sutley (Hall et al., 2018).
LADWP has been working to mitigate heat island impacts in Los Angeles for many years in coordination with the Sustainable City Plan4 and the Los Angeles Resilience Plan,5 and through the City Council designated Committee on Cooling and Urban Heat Impacts. Sutley noted that energy efficiency measures are particularly appealing for LADWP, because reduced peak demand saves customers and the utility money through reduced generation expenses and improved building efficiency results in less waste heat emissions. Since 2010, LADWP has offered incentives for customers that have helped convert more than 7 million sq. ft. and save 1.5 GWh annually, and it is in the process of committing an additional $20 million to fund attic insulation improvements primarily at low-income and multi-family properties. Increasing tree canopy cover for Los Angeles is another heat mitigation strategy LADWP funds through the City Plants program,6 which provides and plants about 22,000 new trees each year in locations that shade buildings and reduce air conditioning use, said Sutley. Using the U.S. Forest Service Eco Smart Landscapes Model,7 ambient cooling from these trees has saved approximately 6 GWh from both direct shading of buildings and indirect effects. The performance of these programs and other LADWP interventions are compared across numerous equity metrics to understand how the benefits are distributed across the city’s residents. Sutley ended with requests for further research into methods to establish near- and long-term cooling targets for city planners and other local officials, more efforts to understand the distribution of impacts across different neighborhoods and communities, and new technologies or strategies to complement existing efforts to combat heat island effects.
ELIZABETH RHOADES, LOS ANGELES COUNTY DEPARTMENT OF PUBLIC HEALTH
Rhoades emphasized the value of evaluating and communicating climate change risks through a public health lens, not only because climate change has direct impacts on human health but also because framing it as a public health issue can elicit stronger support from the public for adaptation and mitigation interventions (Myers et al., 2012). Health is both personal and immediate to an individual, whereas ice loss or other projected damages may seem abstract and far removed from day-to-day life. Los Angeles County has seen an increase in the number of heat-related emergency room visits in recent years, explained Rhoades, and heat-related mortality and morbidity are projected to increase (Knowlton et al., 2011; Ostro et al., 2011). Los Angeles is ill-equipped to adapt to increases in extreme heat, as large segments of the population do not have access to air conditioning (Morello-Frosch et al., 2009). There are also health impacts associated with climate change beyond heat exposure, including declining air quality, more frequent and severe wildfires, and increased transmission of vector-borne disease. Rhoades said that many of these health impacts will disproportionately impact vulnerable populations including low-income communities, children and older adults, outdoor workers and athletes, and undocumented migrants and people experiencing homelessness, in turn contributing to widening disparities and health inequities in California and the United States broadly.
The Los Angeles County Department of Public Health is coordinating with other local agencies to implement heat island mitigation strategies including cool roofs and pavements as well as green spaces and trees. Among these strategies, trees have important public health co-benefits beyond heat mitigation, such as improved air quality and increased physical activity, as well as economic benefits to business owners and residents (Donovan and Butry, 2010). Rhoades also described challenges in emergency preparedness and response to heat health events, identifying several open research questions, as follows:
- Are trigger points for heat warnings based on thresholds shown to cause health impacts?
- Do we evaluate the effectiveness of heat-related messaging?
7 U.S. Department of Agriculture, U.S. Forest Service, “ecoSmart Landscapes,” https://www.fs.usda.gov/ccrc/tools/ecosmart-landscapes.
- Do we track the use and effectiveness of cooling centers?
- Do we use data to ensure that there are cooling centers in the most high need areas?
- Do we use existing syndromic surveillance data on heat-related emergency care to inform health protective measures (such as alerts, targeted messaging, where to site cooling centers) and plan for future extreme heat events?
Elaborating from these questions, Rhoades concluded with several data needs from a public health perspective. Fundamentally, there is a need for improved projections of health-related climate change impacts such as extreme heat, air quality, and vector-borne diseases on which to base public health decisions. Specific to heat, decision makers need better data on how people currently cope during extreme heat events, particularly on the use and efficacy of cooling centers.
Jennifer Jurado, Broward County Chief Resilience Officer, asked two questions: (1) how were communities engaged around placement of weather stations and what would be the infrastructure and cost implications of locating stations in communities as opposed to institutional properties; and (2) did policy makers face challenges in legislating cool roof requirements based on materials or cost considerations on the part of developers or homeowners, which is an issue currently being raised in Southeast Florida. Ban-Weiss responded to the first question, saying that part of the challenge in placing weather stations was that the team initially identified locations based on what made for the best scientific study without considering the difficulty of finding partners that matched those locations. The principal barrier was liability concerns, both for the researchers accessing the equipment as well as potential damage caused by the equipment. When the team connected with Los Angeles Unified School District, the individual schools were each enthusiastic about hosting the station and continue to be engaged through the project. Sutley briefly responded about the political considerations around Los Angeles’s cool roof mandates, saying that the rebates in part address these concerns of cost. She did not consider it a particularly controversial issue, and noted that LADWP incentives were in place before changing the building code and that sequential timing supports adoption.
Johnathan Parfrey, Climate Resolve, noted that cool roofs are predominantly associated with energy efficiency, whereas today’s panel focused on the public health benefits associated with heat mitigation strategies. He asked if there were plans to broaden consideration of the benefits of cool roofs in State legislation. California Energy Commission Chair Robert Weisenmiller described the history of Title 248 building standards and how cool roofs were incorporated, saying that the commission is primarily focused on quantifiable energy savings, although it is in the process of expanding what is included—for example, including residential solar.
A participant asked how the panelists engaged communities and if there are additional challenges to reaching California immigrant communities because of language barriers. Sutley responded that LADWP provides around $1.5 million per year in grants to community organizations to help promote messaging around mitigation strategies such as cool roofs and distributes tens-of-thousands of free fans for individuals who do not have access to air conditioning. This has been a very helpful strategy to reach Los Angeles’s diverse communities, as these organizations are more effective at this type of outreach.
Dan Cayan asked if there are limitations in the scale to which trees and urban forests can be used to combat heat effects due to their water consumption. Rhoades said that their tree planting programs are accompanied by educational campaigns about proper watering practices, as many people believe trees need more water than they actually do. If properly selected, sited, and cared for, she explained, water consumption can be limited, particularly after the tree is established. Sutley added that LADWP tree programs plant only trees that are regionally appropriate and selected for limited water consumption.
An online participant asked whether installing rooftop photovoltaics has cooling impacts and encouraged the panel to comment more broadly on synergies between mitigating climate change impacts through reduced
emissions and adapting to impacts such as extreme heat. Ban-Weiss answered that the heat reduction potential of rooftop solar depends significantly on the roof it is replacing—if installed on top of a conventional dark roof there are cooling benefits, but if installed on top of white roofs they may actually increase heat. Thus, if done strategically to replace conventional dark roofs, rooftop solar can be seen as both a heat adaptation and a climate mitigation strategy, concluded Ban-Weiss.
Ban-Weiss, G. 2018. “Investigating Optimal Urban Heat Mitigation Strategies for Vulnerable Populations in a Changing Climate.” Externally published contribution to California’s Fourth Climate Change Assessment. http://www.climateassessment.ca.gov/techreports/docs/20180827-PublicHealth_External_Ban_Weiss.pdf
Bedsworth, L., D. Cayan, G. Franco, L. Fisher, and S. Ziaja. 2018. “Statewide Summary Report.” California’s Fourth Climate Change Assessment. SUMCCCA4-2018-013. http://www.climateassessment.ca.gov/state/docs/20180827StatewideSummary.pdf
Donovan, G.H., and D.T. Butry. 2010. Trees in the city: Valuing street trees in Portland, Oregon. Landscape and Urban Planning 94:77–83.
Guirguis, K., R. Basu, W.K. Al-Delaimy, T. Benmarhnia, R. Clemesha, I. Corcos, J. Guzman-Morales et al. 2018. Heat, disparities, and health outcomes in San Diego County’s diverse climate zones. GeoHealth. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017GH000127.
Guirguis, K., A. Gershunov, A. Tardy, and R. Basu. 2014. The impact of recent heat waves on human health in California. Journal of Applied Meteorology and Climatology 53(1):3–19.
Hall, A., N. Berg. and K. Reich. 2018. “Los Angeles Summary Report.” California’s Fourth Climate Change Assessment. SUM-CCCA4-2018-007. http://www.climateassessment.ca.gov/regions/docs/20180928-LosAngeles.pdf.
Knowlton, K., M. Rotkin-Ellman, L. Geballe, W. Max, and G.M. Solomon. 2011. Six climate change-related events in the United States accounted for about $14 billion in lost lives and health costs. Health Affairs 30(11):2167–2176.
Morello-Frosch, R., M. Pastor, J. Sadd, and S. Shonkoff. 2009. “The Climate Gap: Inequalities in How Climate Change Hurts Americans and How to Close the Gap.” University of California, Berkeley. https://dornsife.usc.edu/pere/climategap/.
Myers, T.A., M.C. Nisbet, E.W. Maibach, and A.A. Leiserowitz. 2012. A public health frame arouses hopeful emotions about climate change. Climatic Change 113(3–4):1105–1112.
Netburn, D. 2017. “L.A.’s Mayor Wants to Lower the City’s Temperature. These Scientists are Figuring Out How to Do It.” Los Angeles Times. February 9. http://www.latimes.com/projects/la-sci-cooling-los-angeles/.
Ostro, B., S. Rauch, and S. Green. 2011. Quantifying the health impacts of future changes in temperature in California. Environmental Research 111(8):1258–1264.
State of California. 2018. California’s Fourth Climate Change Assessment. http://www.climateassessment.ca.gov/.
Steinberg, N., E. Mazzacurati, J. Turner, C. Gannon, R. Dickinson, M. Snyder, and B. Thrasher. 2018. “Preparing Public Health Officials for Climate Change: A Decision Support Tool.” California’s Fourth Climate Change Assessment. CCCA4-CNRA-2018-012. http://www.climateassessment.ca.gov/techreports/docs/20180827-PublicHealth_CCCA4CNRA-2018-012.pdf.
Taha, H., G. Ban-Weiss, S. Chen, H. Gilbert, H. Goudey, J. Ko, A. Mohegh, et al. 2018a. “Modeling and Observations to Detect Neighborhood-Scale Heat Islands and Inform Effective Countermeasures in Los Angeles.” California’s Fourth Climate Change Assessment. CCCA4-CEC-2018-007. http://www.climateassessment.ca.gov/techreports/docs/20180827Energy_CCCA4-CEC-2018-007.pdf.
Taha, H., R. Levinson, A. Mohegh, H. Gilbert, G. Ban-Weiss, and S. Chen. 2018b. Air-temperature response to neighborhood-scale variations in albedo and canopy cover in the real world: Fine-resolution meteorological modeling and mobile temperature observations in the Los Angeles climate archipelago. Climate 6(2):53.
Vahmani, P., and G.A. Ban-Weiss. 2016. Impact of remotely sensed albedo and vegetation fraction on simulation of urban climate in WRF-urban canopy model: a case study of the urban heat island in Los Angeles. Journal of Geophysical Research: Atmospheres 121(4):1511–1531.
Vahmani, P., F. Sun, A. Hall, and G. Ban-Weiss. 2016. Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California. Environmental Research Letters 11(12):124027.