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Title: Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California

The climate warming effects of accelerated urbanization along with projected global climate change raise an urgent need for sustainable mitigation and adaptation strategies to cool urban climates. Our modeling results show that historical urbanization in the Los Angeles and San Diego metropolitan areas has increased daytime urban air temperature by 1.3 °C, in part due to a weakening of the onshore sea breeze circulation. We find that metropolis-wide adoption of cool roofs can meaningfully offset this daytime warming, reducing temperatures by 0.9 °C relative to a case without cool roofs. Residential cool roofs were responsible for 67% of the cooling. Nocturnal temperature increases of 3.1 °C from urbanization were larger than daytime warming, while nocturnal temperature reductions from cool roofs of 0.5 °C were weaker than corresponding daytime reductions. We further show that cool roof deployment could partially counter the local impacts of global climate change in the Los Angeles metropolitan area. Assuming a scenario in which there are dramatic decreases in greenhouse gas emissions in the 21st century (RCP2.6), mid- and end-of-century temperature increases from global change relative to current climate are similarly reduced by cool roofs from 1.4 °C to 0.6 °C. Assuming a scenario with continued emissionsmore » increases throughout the century (RCP8.5), mid-century warming is significantly reduced by cool roofs from 2.0 °C to 1.0 °C. The end-century warming, however, is significantly offset only in small localized areas containing mostly industrial/commercial buildings where cool roofs with the highest albedo are adopted. We conclude that metropolis-wide adoption of cool roofs can play an important role in mitigating the urban heat island effect, and offsetting near-term local warming from global climate change. Global-scale reductions in greenhouse gas emissions are the only way of avoiding long-term warming, however. We further suggest that both climate mitigation and adaptation can be pursued simultaneously using 'cool photovoltaics'.« less
Authors:
 [1] ;  [2] ;  [3] ; ORCiD logo [1]
  1. Univ. of Southern California, Los Angeles, CA (United States)
  2. Univ. of Missouri, Kansas City, MO (United States); Univ. of California, Los Angeles, CA (United States)
  3. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Grant/Contract Number:
SC0014061; SC0014061:0001
Type:
Published Article
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 11; Journal Issue: 12; Journal ID: ISSN 1748-9326
Publisher:
IOP Publishing
Research Org:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1336485
Alternate Identifier(s):
OSTI ID: 1336486; OSTI ID: 1364377

Vahmani, P., Sun, F., Hall, A., and Ban-Weiss, G.. Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California. United States: N. p., Web. doi:10.1088/1748-9326/11/12/124027.
Vahmani, P., Sun, F., Hall, A., & Ban-Weiss, G.. Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California. United States. doi:10.1088/1748-9326/11/12/124027.
Vahmani, P., Sun, F., Hall, A., and Ban-Weiss, G.. 2016. "Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California". United States. doi:10.1088/1748-9326/11/12/124027.
@article{osti_1336485,
title = {Investigating the climate impacts of urbanization and the potential for cool roofs to counter future climate change in Southern California},
author = {Vahmani, P. and Sun, F. and Hall, A. and Ban-Weiss, G.},
abstractNote = {The climate warming effects of accelerated urbanization along with projected global climate change raise an urgent need for sustainable mitigation and adaptation strategies to cool urban climates. Our modeling results show that historical urbanization in the Los Angeles and San Diego metropolitan areas has increased daytime urban air temperature by 1.3 °C, in part due to a weakening of the onshore sea breeze circulation. We find that metropolis-wide adoption of cool roofs can meaningfully offset this daytime warming, reducing temperatures by 0.9 °C relative to a case without cool roofs. Residential cool roofs were responsible for 67% of the cooling. Nocturnal temperature increases of 3.1 °C from urbanization were larger than daytime warming, while nocturnal temperature reductions from cool roofs of 0.5 °C were weaker than corresponding daytime reductions. We further show that cool roof deployment could partially counter the local impacts of global climate change in the Los Angeles metropolitan area. Assuming a scenario in which there are dramatic decreases in greenhouse gas emissions in the 21st century (RCP2.6), mid- and end-of-century temperature increases from global change relative to current climate are similarly reduced by cool roofs from 1.4 °C to 0.6 °C. Assuming a scenario with continued emissions increases throughout the century (RCP8.5), mid-century warming is significantly reduced by cool roofs from 2.0 °C to 1.0 °C. The end-century warming, however, is significantly offset only in small localized areas containing mostly industrial/commercial buildings where cool roofs with the highest albedo are adopted. We conclude that metropolis-wide adoption of cool roofs can play an important role in mitigating the urban heat island effect, and offsetting near-term local warming from global climate change. Global-scale reductions in greenhouse gas emissions are the only way of avoiding long-term warming, however. We further suggest that both climate mitigation and adaptation can be pursued simultaneously using 'cool photovoltaics'.},
doi = {10.1088/1748-9326/11/12/124027},
journal = {Environmental Research Letters},
number = 12,
volume = 11,
place = {United States},
year = {2016},
month = {12}
}