The radiative forcing benefits of “cool roof” construction in California: quantifying the climate impacts of building albedo modification
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Exploiting surface albedo change has been proposed as a form of geoengineering to reduce the heating effect of anthropogenic increases in greenhouse gases (GHGs). Recent modeling experiments have projected significant negative radiative forcing from large-scale implementation of albedo reduction technologies (“cool” roofs and pavements). This paper complements such model studies with measurement-based calculations of the direct radiation balance impacts of replacement of conventional roofing with “cool” roof materials in California. This analysis uses, as a case study, the required changes to commercial buildings embodied in California’s building energy efficiency regulations, representing a total of 4300 ha of roof area distributed over 16 climate zones. The estimated statewide mean radiative forcing per 0.01 increase in albedo (here labeled RF01) is −1.38 W/m2. The resulting unit-roof-area mean annual radiative forcing impact of this regulation is −44.2 W/m2. This forcing is computed to counteract the positive radiative forcing of ambient atmospheric CO2 at a rate of about 41 kg for each square meter of roof. Aggregated over the 4300 ha of cool roof estimated built in the first decade after adoption of the State regulation, this is comparable to removing about 1.76 million metric tons (MMT) of CO2 from the atmosphere. The point radiation data used in this study also provide perspective on the spatial variability of cool roof radiative forcing in California, with individual climate zone effectiveness ranging from −37 to −59 W/m2 of roof. These “bottom-up” calculations validate the estimates reported for published “top down” modeling, highlight the large spatial diversity of the effects of albedo change within even a limited geographical area, and offer a potential methodology for regulatory agencies to account for the climate effects of “cool” roofing in addition to its well-known energy efficiency benefits.
KeywordsGeneral Circulation Model Surface Albedo Commercial Building Solar Radiation Data Surface Solar Radiation
I would like to thank the California Air Resources Board for supporting this research, and the efforts of one reviewer whose close reading and timely suggestions greatly improved this paper.
The contents of this report and opinions expressed herein are the work of the author alone, and do not represent official statements or policies of the California Air Resources Board or of the State of California. Any mention of commercial products does not imply an endorsement by California Air Resources Board or of the State of California.
- Akbari H, Konopacki S (2005) Calculating energy-saving potentials of heat-island reduction strategies. Energy Policy 33:721–756Google Scholar
- Akbari H, Menon S, Rosenfeld A (2009) Global cooling: increasing world-wide urban albedos to offset CO2. Climatic Change 95Google Scholar
- Budyko MI (1969) The effect of solar radiation variations on the climate of the Earth, Tellus XXI(5)Google Scholar
- Chapin FS, Sturm M, Serreze MC, McFadden JP, Key JR, Lloyd AH, McGuire AD, Rupp TS, Lynch AH, Schimel JP, Beringer J, Chapman WL, Epstein HE, Euskirchen ES, Hinzman LD, Jia G, Ping C-L, Tape KD, Thompson CDC, Walker DA, Welker JM (2005) Role of land-surface changes in arctic summer warming. Science 310:657–660CrossRefGoogle Scholar
- CIMIS (California Irrigation Management Information System) (2010) California Department of Water Resources, http://www.nd.water.ca.gov/PPAs/WaterConservation/CIMIS/
- GISS (Goddard Institute for Space Studies) (2011) Atmosphere – Ocean Model, http://aom.giss.nasa.gov/solar.html
- Google Maps (2010) (http://maps.google.com/maps), Google, Inc., Mountain View, California
- Hansen J, Sato M, Ruedy R, Nazarenko L, Lacis A, Schmidt GA, Russell G, Aleinov I, Bauer M, Bauer S, Bell N, Cairns B, Canuto V, Chandler M, Cheng Y, Del Genio A, Faluvegi G, Fleming E, Friend A, Hall T, Jackman C, Kelley M, Kiang N, Koch D, Lean J, Lerner J, Lo K, Menon S, Miller R, Minnis P, Novakov T, Oinas V, Ja Perlwitz, Ju Perlwitz, Rind D, Romanou A, Shindell D, Stone P, Sun S, Tausnev N, Thresher D, Wielicki B, Wong T, Yao M, Zhang S (2005) Efficacy of climate forcings. J Geophys Res 110:D18104CrossRefGoogle Scholar
- IPCC (2007) In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds) Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge University Press, CambridgeGoogle Scholar
- Lenton TM, Vaughan NE (2009) The radiative forcing potential of different climate geoengineering options. Atmos Chem Phys 9:5539–5561Google Scholar
- Menon S, Akbari1 H, Mahanama S, Sednev I, Levinson R (2010) Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets, Env Res Lett 5Google Scholar
- NOAA (U.S. National Oceanic and Atmospheric Administration) (2011) Current CO2 monitoring data for Mauna Loa, Hawaii, ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt
- Rosenzweig C, Solecki W, Slosberg R (2006) Mitigating New York City’s Heat Island with Urban Forestry, Living Roofs, and Light Surfaces, NYSERDA 06–06Google Scholar
- Sagan C, Toon O, Pollack J (1979) Anthropogenic albedo changes and the earth’s climate. Science 206(4425):1363–1368Google Scholar
- Taha H, Chang SC, Akbari H (2000) Meteorological and Air Quality Impacts of Heat Island Mitigation Measures In Three U.S. Cities, Lawrence Berkeley National Laboratory Report LBNL-44222, Berkeley, CAGoogle Scholar