In 2008—and again in 2012—the Canadian company TransCanada submitted to the U.S. Department of State an application for a Presidential Permit authorizing construction and operation of pipeline facilities to import crude oil across the U.S.-Canada border. The proposed Keystone XL Pipeline would transport crude oil derived from Canadian oil sands deposits in Alberta as well as crude oil produced from the Bakken region in North Dakota and Montana to a market hub in Nebraska for further delivery to U.S. Gulf Coast refineries. A decision to issue or deny the Presidential Permit on the project is based on the U.S. Department of State's determination of whether the proposed pipeline serves the national interest. A national interest determination rests on a number of factors, including energy security; foreign policy; environmental, social, and economic impacts; and compliance with relevant federal regulations. On June 25, 2013, President Obama announced a national "Climate Action Plan" to reduce emissions of carbon dioxide (CO 2 ) and other greenhouse gases (GHG), as well as to encourage adaptation to expected climate change. During his speech, the President made reference to the proposed Keystone XL Pipeline and stated that an evaluation of the pipeline's impact on climate change would factor into the State Department's national interest determination: Allowing the Keystone pipeline to be built requires a finding that doing so would be in our nation's interest. And our national interest will be served only if this project does not significantly exacerbate the problem of carbon pollution. The net effects of the pipeline's impact on our climate will be absolutely critical to determining whether this project is allowed to go forward. Both supporters and opponents of the proposed Keystone XL Pipeline reacted positively to the President's comments, signaling that an assessment of the net effects of the pipeline's impact on the climate—as well as the significance of those effects—is still under intense debate. The effects of the proposed Keystone XL Pipeline on climate change could be analyzed, in part, by an assessment of the GHG emissions attributable to the project. Such an analysis could encompass a variety of activities and implications relative to the pipeline, including the GHG emissions associated with the proposed pipeline's construction and operation, as well as the GHG emissions attributable to the crude oils that would be transported through the pipeline. An assessment would be dependent upon many factors, most notably, the availability and quality of GHG emissions data for the industry, the scope of industry activities included within the assessment, and the assumptions made about how to model these activities. Many secondary considerations may also impact an assessment. These include assumptions regarding global crude oil markets, refinery inputs and outputs, transport options, economics, policy considerations, and the end-use consumption of petroleum products. Different values attached to these varying factors return different estimates for the GHG emissions attributable to the construction and operation of the proposed pipeline as well as the crude oils transported through it. A number of publicly available studies have attempted to assess the GHG emissions of crude oils derived from Canadian oil sands deposits ("oil sands crudes"). Some of these studies have also made estimates for the GHG emissions attributable to the crude oils that would be transported through the proposed pipeline. The State Department, in its March 2013 Draft Environmental Impact Statement ( DEIS ) for the Keystone XL Pipeline, has produced one such assessment. As the DEIS will be a primary component for the national interest determination, this report focuses on the State Department's analysis and comments on its methodology and conclusions. Where applicable, the report supplements the DEIS analysis with relevant additional information. As the State Department's assessment is based on the findings of several published studies of oil sands crudes, this report also comments on their respective methodologies and conclusions. For a more extensive investigation of the GHG emissions assessments of oil sands crudes and their comparison to other global crude oils ("reference crudes"), see CRS Report R42537, Canadian Oil Sands: Life-Cycle Assessments of Greenhouse Gas Emissions , by [author name scrubbed]. The DEIS includes an analysis of the GHG emissions that would be attributable to the proposed Keystone XL Pipeline. It reports both "direct" GHG emissions from the construction and operation of the proposed pipeline as well as "indirect" emissions attributed to the production and use of the oil sands crudes that would be transported through the proposed pipeline. The State Department defines the indirect GHG emissions as "incremental GHG emissions." This value is generated by examining the full GHG emissions profile of oil sands crudes (i.e., the aggregate GHG emissions released by all activities from the extraction of the resource to the end-use combustion of refined fuels), comparing this profile to those of other reference crudes it may displace in U.S. refineries, and then estimating the difference between a scenario where the proposed Keystone XL Pipeline is constructed and a scenario where it is not. Thus, for the purposes of its analysis, the State Department incorporates the direct emissions attributed to the operation of the pipeline into the reported incremental indirect emissions. Based on its review of the available GHG emissions assessments, as well as an analysis of North American crude oil transport infrastructure and global crude oil markets , the State Department finds the following: Approval or denial of the proposed Project is unlikely to have a substantial impact on the rate of development in the oil sands, or on the amount of heavy crude oil refined in the Gulf Coast area. If the proposed Keystone XL Pipeline were not built, but other proposed pipelines were (e.g., the Northern Gateway, the Trans Mountain expansion, and the TransCanada proposal to ship crude oil east to Ontario), there would be a 0.4%-0.6% reduction in Canadian oil sands production by 2030, and a decrease in the incremental indirect life-cycle GHG emissions of oil sands production in the range of 0.07-0.83 million metric tons of carbon dioxide equivalents (MMTCO 2 e) annually. If all proposed pipelines were denied, there would be a 2%-4% reduction in Canadian oil sands production by 2030, and a decrease in the incremental indirect life-cycle GHG emissions of oil sands production in the range of 0.35-5.30 MMTCO 2 e annually. In summary, the DEIS reports that the proposed Keystone XL Pipeline "would be responsible for incremental GHG emissions in the range of 0.07 ... 5.30 MMTCO 2 e annually," and places these numbers in context by noting U.S. GHG emissions totaled 6,822 MMTCO 2 e in 2010 (excluding emissions/removals from land use, land-use change, and forestry), and global CO 2 emissions from fuel combustion totaled 30,326 MMCO 2 e. The incremental pipeline emissions would represent an increase of 0.001%-0.08% over the total domestic GHG inventory for the United States in 2010 and would be equivalent, at most, to the annual GHG emissions from the energy used in a little over 1 million passenger vehicles or the annual CO 2 emissions from the energy used in a little over a quarter million homes in the United States. See Table A-1 for a summary of this estimate as well as other selected pipeline scenarios and their GHG equivalencies. The proposed Project would be responsible for incremental GHG emissions in the range of 0.07 ... 5.30 MMTCO 2 e annually. How does the State Department calculate this estimate, and what does it say about the cumulative effects of the pipeline? The State Department's first step in calculating the GHG emissions attributable to the proposed pipeline is to develop a "life-cycle assessment" of the Canadian oil sands resource. Life-cycle assessment (LCA) is an analytic method used for evaluating and comparing the environmental impacts of various products (in this case, the climate change implications of a petroleum resource). LCAs can be used in this way to identify, quantify, and track emissions of carbon dioxide and other GHG emissions arising from the development of the resource, and to express them in a single, universal metric of carbon dioxide equivalent (CO 2 e) GHG emissions per unit of fuel or fuel use. This figure is commonly referred to as the "emissions intensity" of the fuel. The results of an LCA can be used to evaluate the GHG emissions intensity of various stages of the fuel's life-cycle, as well as to compare the emissions intensity of one type of fuel or method of production to another. Emissions intensities modeled by LCAs are delimited by the scope of activities chosen to be in the assessment. Many LCAs are based on a set of boundaries commonly referred to as "cradle-to-grave," or, in the case of transportation fuels such as petroleum, "Well-to-Wheels" (WTW). WTW assessments focus on the emissions associated with the entire life-cycle of the fuel, from extraction, transport, and refining of crude oil; to the distribution of refined product to retail markets (e.g., gasoline, diesel, jet fuel); to the combustion of the fuel in end-use vehicles. The State Department has chosen a WTW assessment for the DEIS. Other analyses have used different sets of boundaries to compare the relative impact of oil sands crudes against reference crudes. Other choices include Well-to-Tank (WTT) or Well-to-Refinery Gate (WTR), and each establish different (i.e., more specific) life-cycle boundaries to evaluate emissions. Inclusion of the final combustion phase allows for the most complete picture of petroleum's impact on GHG emissions, as this phase can contribute up to 70%-80% of WTW emissions. However, other boundaries can be used to highlight the differences in emissions associated with particular stages as well as experiment with certain boundary assumptions.