Predictions of global energy use in the next century suggest a continued increase in carbon emissions and rising concentrations of carbon dioxide in the atmosphere unless major changes are made in the way we produce and use energy. The Intergovernmental Panel on Climate Change predicts, for example, a doubling of atmospheric carbon dioxide ([CO.sub.2]) concentration by 2050, with accelerating rates of increase beyond that. By preventing heat radiated from the sun-warmed Earth from escaping into space, the increased concentration of [CO.sub.2] in the atmosphere contributes to climate change. Many scientists agree that a doubling of atmospheric [CO.sub.2] concentrations could have a variety of serious environmental consequences, including rising sea levels, more-turbulent weather, and an increased incidence of drought.
The gases that produce the greenhouse effect are [CO.sub.2], methane ([CH.sub.4]), nitrous oxide ([N.sub.2]O), and a host of engineered chemicals such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). About 90 percent of U.S. greenhouse emissions from anthropogenic sources come from energy production and use, mostly as byproducts of the combustion of fossil fuels. Greenhouse gas emissions can be reduced significantly by using energy more efficiently and by using fuels with lower carbon content.
Each of the three energy end-use sectors--buildings, industry, and transportation--account for approximately one-third of [CO.sub.2] emissions in the United States. Production of electricity production, which is used primarily to heat, cool, and light buildings and to power motors and other equipment in industry, produces 37 percent of the nation's [CO.sub.2]. This diversity of sources and uses of fossil energy means that no single technological "fix" exists for reducing [CO.sub.2] emissions. However, a growing body of literature suggests that significant improvements in energy efficiency are possible in residential and commercial buildings, industrial processes, and transportation. A recent assessment of technology opportunities demonstrates that, with the help of a supportive public policy, the United States could reduce its [CO.sub.2] emissions at no net cost to the economy.
A Clean Energy Future
Scenarios for a Clean Energy Future, a study commissioned by the U.S. Department of Energy and co-funded by the U.S. Environmental Protection Agency, is the most comprehensive assessment to date of technology- and market-based opportunities designed to address the United States' current and upcoming energy challenges. (1) The study, conducted by researchers at five DOE National Laboratories, was designed to assess how energy-efficient and clean-energy technologies can address key energy and environmental challenges of the next century while allowing continued economic growth. One goal was to identify policy implementation pathways that can form the basis for attractive national solutions. The time horizon of the analysis is 2020.
The study presented three primary scenarios: a business-as-usual forecast and two potential alternatives to current policy that reflect higher levels of public commitment and political resolve to solving the nation's energy-related problems.
The business-as-usual forecast assumes that current energy policies and programs will continue. This results in the continued rapid growth of energy consumption and [CO.sub.2] emissions, despite a steady pace of technological progress and improved efficiencies.
The moderate scenario assumes the adoption of market-based policies, including a 50-percent increase in cost-shared federal energy research and development, expanded voluntary programs, and tax credits for efficient appliances, vehicles, and non-hydro renewable electricity.
The advanced scenario is defined by more-aggressive policies including a doubling of federal energy research and development, voluntary agreements …