Paper Title

Paper Title: Los Angeles’ Experience in Quantifying the Benefits of and Implementing Strategies to Mitigate the Urban Heat Island Effect

The City of Los Angeles (City) is leading the effort to implement strategies to reduce the urban heat island effect in southern California and is working to quantify the potential air quality impacts from these strategies. This paper describes the actions taken to date, identifies obstacles and barriers, and discusses forthcoming efforts. In particular, Los Angeles has taken a leadership role in three elements of the urban heat island effort that can serve as a model for other government agencies both locally and beyond. These are:

1) to quantify the air quality benefits of urban heat island mitigation strategies so that they can be used for air quality planning and implementation;

2) to implement heat island mitigation strategies to physically demonstrate their benefits; and

3) to promote the implementation of these strategies in the private sector through regulatory and incentive-based approaches.

The City of Los Angeles, which comprises 485 square miles and contains a population of 3.7 million people, is located in the northwest portion of the South Coast Air Basin (SoCAB) that encompasses over 10,000 square miles and contains nearly 15 million people in all or part of four counties. Given the size of this airshed, it will ultimately require the cooperation of many different cities, counties, utilities, and other agencies to fully develop and implement a comprehensive heat island mitigation program in southern California. With this in mind, the City of Los Angeles has begun this process and has learned many important lessons that can benefit government agencies interested in addressing urban heat islands.

Quantifying the Air Quality Benefits of Urban Heat Island Mitigation Strategies

The urban heat island effect in Los Angeles has been the subject of numerous scientific studies and reports for more than a decade coincident with the creation of the Heat Island Research Project (later renamed the Heat Island Group) at the Lawrence Berkeley National Laboratory (LBNL) in 1985[i]. The focus on Los Angeles for the study of heat islands was a logical choice given the region’s well-known urbanization, smog, and hot summers. Additionally, photochemical, meteorological, and emission models for the Los Angeles region are well-developed for air quality planning purposes and these models have been able to be applied to the study of the air quality impacts of heat island mitigation strategies.

The Lawrence Berkeley National Laboratory undertook the first efforts to apply meteorological and photochemical modeling tools to quantify the air quality benefits of urban heat island mitigation strategies in Los Angeles in 1994 and again in 1996 and 1997.[ii] In 1998, the South Coast Air Quality Management District (SCAQMD) contracted with ENVIRON International Corporation (ENVIRON) to further investigate the potential effectiveness of an urban heat island program by sponsoring another study into the subject.[iii] While both studies indicated that moderate increases in albedo and vegetation would reduce ozone concentrations in the SoCAB, the SCAQMD/ENVIRON study’s results were less pronounced than those of LBNL due to a number of technical differences in approach.

In 2000, the City of Los Angeles sought to pursue the potential of using heat island mitigation strategies to generate tradable emission reduction credits that it could then use to further support its tree planting programs. To do so, the Environmental Affairs Department (EAD) of the City of Los Angeles developed a partnership with the U.S. Environmental Protection Agency (EPA), the U.S. Department of Energy (DOE), and LBNL. The EAD then contracted with ENVIRON, who worked closely together with LBNL to revisit and reconcile the previous modeling efforts and conduct a new set of modeling based on that reconciliation.[iv] This work demonstrated consistent results with the previous modeling, although still less pronounced than the earlier work.

The results of this partnership effort were presented to the SCAQMD in 2000, and the City sponsored a subsequent analysis that was prepared by ENVIRON on the development of an emission reduction credit program that was presented to the SCAMD in the summer of 2001.[v] This analysis explored the types of emission reductions that could be directly and indirectly associated with heat island mitigation strategies and identified areas of uncertainty that remained in the modeling. Finally, this analysis explored the potential methods for generating emission reduction credits from these measures.

At the urging of the City of Los Angeles and others, the SCAQMD has now agreed to perform a more comprehensive analysis by modeling each day of the year, rather than focusing on a single episode as the previous efforts have done. The results of this study should be available in the Fall of 2002 and will be critical to understanding how changes in vegetation and albedo affect the generation of ozone and the transport of ozone precursors (NOx and VOCs) over a variety of meteorological conditions.

Additionally, the City of Los Angeles, along with stakeholders from throughout the United States, has also been strongly pressing the U.S. EPA to provide guidance on how heat island mitigation strategies can be included in State Implementation Plan (SIP) as a creditable measure. EPA has now committed to drafting a guidance document for allowing “innovative strategies” to form part of a SIP. This guidance, along with the advanced modeling work that the SCAQMD will be conducting, should substantially further the inclusion of heat island strategies in the air quality regulatory arena.

The City of Los Angeles has also taken a leadership role in implementing heat island mitigation strategies. Since 1990, the City, in partnership with local community-based organizations, has had an aggressive tree planting program that has resulted in the planting of over 80,000 trees at schools, on City streets, in parks, at residences, and in local forests.[vi] Not only do these programs provide tremendous environmental benefits, but they also have employed hundreds of at-risk youth who have received important job skills, education, and training. Additionally, in the next several years the Los Angeles Department of Water and Power (LADWP) is expected to plant over 200,000 trees on private property to provide shading on air conditioners and buildings and the EAD, along with its community partners, anticipates planting an additional 40,000 trees. As a result of these and other urban forestry efforts, the City of Los Angeles has, for the past 15 years, been designated as a Tree City USA by the National Arbor Day Foundation.[vii]

As part of its commitment to energy efficiency, urban heat island mitigation, and reducing the emission of greenhouse gases, the City of Los Angeles adopted a policy in 2001 requiring that Energy Star^® compliant roofing materials be used on all City facilities whenever a new roof is installed or an existing roof replaced.[viii] Since the City owns and operates over 800 facilities, this policy will result in the conversion of more than 1 million square feet of roof to high albedo, low emissive roofing materials over the course of the next ten years.

The EAD is now developing a partnership with the SCAQMD, LADWP, the California Energy Commission (CEC), the Los Angeles Unified School District (LAUSD), the Los Angeles Zoo, community-based organizations, and the cement industry. Through this effort, the EAD will build a heat island mitigation demonstration site adjacent to the Los Angeles Zoo that will include the installation of cool roofs at a magnet high school, whitetopping of a 2 acre parking lot, planting of shade trees, and installation of vine-covered trellises for shading parking spots. This site, which will also house the Los Angeles Observatory, will provide both scientific data on the effects of these strategies as well as an educational opportunity for decision-makers and the public.

In adopting a comprehensive new landscape ordinance in 1996, the City of Los Angeles took its first formal action concerning the urban heat island effect in Los Angeles.[ix] While primarily focused on promoting native vegetation, reducing the demand for landscape water, and reducing stormwater runoff, this ordinance explicitly recognizes the role of trees in mitigating the urban heat island effect. Among other provisions, the ordinance requires the planting of one tree per 500 square feet of landscaped area in commercial and residential developments and requires the planting of one tree per 4 parking spaces in most commercial parking lots to achieve a canopy of 50% of the parking lot area within 10 years.

The City of Los Angeles, in partnership with the CEC, has also implemented a Cool Roof Incentive Program that provides a cash incentive to property owners who replace their existing flat or low-sloped dark roof with an Energy Star^® compliant roofing material. Initiated by the CEC in early 2001 as one of several energy-efficiency responses to the growing energy crisis in California, this program has provided incentives for the installation of over 2.4 million square feet of roofs in Los Angeles.

By taking an active role in the quantification and implementation of strategies to reduce the urban heat island effect, the City of Los Angeles has initiated and continues to implement several successful programs leading to reduced energy demand and improved air quality, and has identified and addressed numerous institutional, enforcement, and market transformation barriers to the quantification and implementation process

Gary Gero is the Assistant General Manager of the City of Los Angeles Environmental Affairs Department where he has worked since the department’s creation in 1990. Previously he served as the department’s Director of Air Quality. His primary focus for the past decade has been on legislative and policy issues related to air quality, energy, and sustainability. Mr. Gero has served as the chair of the City’s task force on alternative fuel vehicles, developed a Sustainable Building Guidebook to promote environmentally-sound building practices, led the development of the Los Angeles Energy Climate Action Plan, and is currently overseeing the City’s urban heat island reduction program to promote strategic tree planting and the use of light-colored roofing and paving materials. He has also served as an Instructor in Environmental Public Policy for the UCLA Extension program. Gary received undergraduate degrees from the University of California at Berkeley and holds a Master of Science degree from the London School of Economics in London, England.

[i] Rosenfeld, A. 1999. “The Art of Energy Efficiency: Protecting the Environment with Better Technology,” Annual Review of Energy and the Environment, 1999 - 24:33-82

[ii] Taha, H (ed). 1994. ibid; Taha H. 1996. “Modeling the Impacts of Increased Urban Vegetation on the Ozone Air Quality in the South Coast Air Basin,“ Atmospheric Environment, 30(20), pp. 3423-3430 also Lawrence Berkeley National Laboratory Report LBL-37317, Berkeley, California; and Taha, H. 1997. "Modeling the Impacts of Large-scale Albedo Changes on Ozone Air Quality in the South Coast Air Basin," Atmospheric Environment, 31(11), pp. 1667-1676 also Lawrence Berkeley National Laboratory Report LBL-36890, Berkeley, CA.

[iii] ENVIRON. 1998. “Air Quality Modeling Evaluation of the ‘Cool Communities’ Ozone Control Strategy.”

[iv] ENVIRON and LBNL for the City of Los Angeles, 2000 “Reconciliation of Two Modeling Efforts that Estimate the Air Quality Benefits of Cool Communities Strategies in the South Coast Air Basin; and ENVIRON and LBNL for the City of Los Angeles, 2000 “Result of Cool Communities Modeling of the 1997 AQMP Year 2010 Control Scenario”

[v] ENVIRON for the City of Los Angeles, 2001 “Development of an Ozone Precursor Emission Reduction Credit Program Based on Urban Heat Island Mitigation Measures”

[vi] City of Los Angeles, 2001 “Climate Energy Action Plan”

[vii] David Evans and Associates for the LADWP, 2001, “Draft Final Report – City of Los Angeles Urban Forest Assessment”

[viii] Los Angeles City Council, 2001, “Cool Roof Incentive Program”

[ix] City of Los Angeles. 1996, Landscape Ordinance, Ordinance No. 170,978 (as amended)