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Abstract The albedo of a roof determines the fraction of incoming sunlight that is reflected, which affects heat transfer into the building and exchange of energy between the built environment and the atmosphere. While the albedo of individual roofs can be easily measured, roof albedo at the city scale is unknown. In this paper we characterize the albedos of roofs in seven cities in California: Los Angeles, Long Beach, Bakersfield, San Francisco, San Jose, Sacramento, and San Diego. The fraction of urban area covered by roofs ranged by city from 10% to 25%. City-wide average roof albedo ranged from 0.17 ± 0.08 to 0.20 ± 0.11 (mean ± standard deviation) for five of the cities; values were higher in Sacramento (0.24 ± 0.11) and San Diego (0.29 ± 0.15). Buildings with small roofs were found to constitute a large fraction of city roof area and to have low mean albedos. This suggests that efforts to increase urban albedo through the use of reflective roofs should include small roofs, which are presumably mostly residential. Roof albedos derived for Bakersfield were used in a regional climate model (Weather Research and Forecasting Model) to estimate temperature changes attainable by converting the current stock of roofs to “cool” high albedo roofs. It was found that seasonal mean afternoon (15:00 LST) temperatures could be reduced by up to 0.2 °C during both the summer and winter. Changes in precipitation were not significant at the 95% confidence level.

Integrated assessment models show that, without new climate policies, abundant supplies of natural gas will have little impact on greenhouse-gas emissions and climate change. See Letter p.482 The development of hydraulic fracturing technologies has led to rapid growth in the use natural gas as an energy source. Some evidence has suggested that this growing adoption of natural gas might lead to a reduced greenhouse gas burden and consequent mitigation of climate change. This collaboration between five energy–climate modelling teams show that instead — under a scenario of abundant natural gas availability — increased consumption will have little or no impact on climate change. The authors suggest that expanded natural gas production and use is neither a substitute for a climate policy in the decades ahead nor a major new complication to the anthropogenic emissions problem.

Abstract Average energy consumption per U.S. household has fallen by just under 20% in the last ten years. Much of this drop occurred after 1979, when gas and electricity prices as well as oil prices rose in real terms. The response of households to higher prices has involved physical modifications on and in the home and changes in behavior. Many actions have been taken by households, but the most important single factor has been a significant reduction in indoor temperatures. The greater energy efficiency of new homes and appliances has also helped to depress residential energy demand, although improvements have levelled off in the last few years. There are signs that the momentum of energy conservation is less now than it was 2 years ago, but it appears that energy prices will be high enough to discourage households from returning to former energy-using practices. Along with the continued replacement of homes and appliances with more efficient models, and other factors such as the migration to wanner regions and the movement to more apartments and smaller homes, this will probably keep U.S. residential energy consumption at about its present level through the 1980s.

As the world searches for renewable energy in the face of climate change and China attempts to expand its power supply to further its economic development, hydroelectricity has moved to the top of the country’s energy agenda. This has given rise to a new form of “hydropower discourse” in China. The discourse is underpinned by the ideas of environmental protection and sustainable development, which are widely perceived as unobjectionable in view of the current availability of resources. This article argues that the apparent ethical pursuit of renewable energy by building dams to generate electricity masks relations of dominance and helps to enable large energy companies, political leaders, and regional decision makers to pursue their interests against those who have limited or no access to the knowledge and capital employed in the development process. It will examine the ideological assumptions and institutional rootedness of hydropower discourse, and the power relations embedded in it.

Abstract Plug-in hybrid electric vehicles (PHEVs) consume both gasoline and grid electricity. The corresponding temporal energy consumption and emission trends are valuable to investigate in order to fully understand the environmental benefits. The 24-h energy consumption and emission profile depends on different vehicle designs, driving, and charging scenarios. This study assesses the potential energy impact of PHEVs by considering different charging scenarios defined by different charging power levels, locations, and charging time. The region selected for the study is the South Coast Air Basin of California. Driving behaviors are derived from the National Household Travel Survey 2009 (NHTS 2009) and vehicle parameters are based on realistic assumptions consistent with projected vehicle deployments. Results show that the reduction in petroleum consumption is significant compared to standard gasoline vehicles and the ability to operate on electricity alone is crucial to cold start emission reduction. The benefit of higher power charging on petroleum consumption is small. Delayed and average charging are better than immediate charging for home, and non-home charging increases peak grid loads.

It is beyond credible dispute that the planet is heating up at an alarming rate and that the ecological effects of global warming pose real questions about the continued viability of human and non-human life on earth in the not-too-distant future. A primary cause of global warming is the burning of carbon-based fuels to generate electricity. Clearly, more must be done, and done soon, to stave off the worst impacts of global warming. Drastically reducing global carbon emissions features prominently in any serious proposal to combat global warming. However, given that humans are extremely unlikely to willingly give up the massive recreational, economic, health, and quality-of-life benefits that come from having access to plentiful, cheap, and reliable electricity, any reductions in carbon-generated electricity will likely have to be made up for by massive increases in non-carbon-based means of generation, such as wind, solar, and hydroelectricity. Aside from nuclear power, hydropower is the most heavily regulated electricity generating source in the U.S. The current regulations governing small hydropower discourage investment and unnecessarily burden developers by requiring them to navigate a costly, complex, and time-consuming regulatory framework that may be appropriate for large dams given the environmental and ecological damage such dams can cause, but are regulatory overkill for the comparatively small impacts from a small hydro project. With low-impact small hydropower technologies offering a politically-promising approach to utilizing untapped hydropower potential in America, while also allowing fisheries to thrive and rivers to run free, this regulatory scheme is ripe for reform. The article offers targeted suggestions for reform to the federal oversight of small hydropower licensing, with a particular focus on making a regulatory distinction between low-impact and more physically-intrusive methods of hydropower generation and streamlining and expediting the approval process for low impact small hydropower projects.

E RNEST O RLANDO L AWRENCE B ERKELEY N ATIONAL L ABORATORY Status of China’s Energy Efficiency Standards and Labels for Appliances and International Collaboration Nan Zhou Environmental Energy Technologies Division March 2008 This work described in this report was funded by the Ministry of Economy, Trade and Industry and the Institute of Energy Economics, Japan. This work was supported by the Environmental Protection Agency, Office of Atmospheric Programs through the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 i

Abstract The reduction in energy-related manufacturing carbon dioxide emissions for nine OECD countries for 1973–87 is analysed. Carbon dioxide emissions are estimated from energy use data. The emphasis is on carbon dioxide intensities, defined as emissions divided by value added. The overall manufacturing carbon dioxide intensity was reduced by 42% in the period. Four fuels are specified together with six subsectors of manufacturing. A Divisia index approach is used to evaluate the contribution to reduced carbon dioxide intensity from different components. The main contribution to reduced carbon dioxide intensity is from the general reduction in manufacturing energy intensity, most likely driven by economic growth and increased energy prices, giving incentives to invest in new technology and industrial processes. There is also a significant contribution from reduced production in the most carbon dioxide intensive subsectors, and a contribution from higher efficiency in electricity generation together with a larger nuclear power share at the expense of oil.