Energy and Carbon Dioxide Emission Data Uncertainties

As nations complete national inventories of carbon dioxide emissions and attempt to achieve emissions reduction targets as part of international treaty obligations, independent verification of reported emissions becomes essential. However, organizations that report carbon dioxide emissions utilize different methods and produce data that are not directly comparable with each other, making verification of national inventories and climate modeling efforts difficult and potentially misleading. Carbon emission estimates are based directly on energy use statistics. Unfortunately, there is great unrecognized uncertainty and differences among organizations that independently report energy use statistics. International energy data reporting organizations include different energy sources, utilize different calorific contents of fossil fuels, and utilize different and inconsistent primary energy equivalencies in their annual statistics. Thus although British Petroleum (BP) and the US Energy Information Administration (EIA) report identical quantities of barrels of oil consumed in 2005, the energy content reported differs by over 11%, or 18 Exajoules, roughly double the primary energy supply of the United Kingdom. These energy discrepancies and different methods persist in carbon emission statistics due to improper choices of fossil fuel emission factors. Furthermore, carbon dioxide statistical organizations all use different accounting methods, include different emission sources, and have different definitions of similarly named emission categories. Differences in reported carbon dioxide emissions for the United States in 2005 by EIA and the US Carbon Dioxide Information Analysis Center (CDIAC), both part of the US Department of Energy, are over .22 Pg CO2. These discrepancies could greatly affect attempts to develop a global emission trading market. The differences in reported data and methods make comparisons across organizations challenging, and often misleading. Indeed, these differences can mislead researchers and climate modelers as easily as policymakers. A recent and often-cited publication by Raupach et al., does not adequately address the full uncertainty of carbon emission reports and comes to a faulty conclusion that the world has exceeded the highest and most extreme Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES). Additionally, using different data sources for analyses such as carbon intensities may lead to contradictory results, depending on what assumptions are behind the energy and carbon dioxide statistics. To facilitate improved understanding of uncertainties and different methodologies of reporting organizations, this paper introduces an online database that consolidates energy and carbon emission reports and allows users to view all organizations' data in consistent units side-by-side. Furthermore, the database offers the ability to apply consistent methodological assumptions to all organizations' data. This harmonization does not rectify all discrepancies between organizations, however, especially those resulting from differing fossil fuel calorific values and emission factors. Reporting organizations should develop consistent interagency terminology and standards, and researchers and policymakers utilizing these data should explicitly state assumptions behind these data.