A Model for Estimating Future Emissions of Sulfur Hexafluoride and Perfluorocarbons

Sulfur hexafluoride (SF6), perfluoromethane (CF4) and perfluoroethane (C2F6) are strong greenhouse gases with long atmospheric residence times. Under the Kyoto Protocol to the Framework Convention on Climate Change adopted in December 1997, industrialized nations agreed to regulate their emissions of these gases. Here we present a simple spreadsheet model that is useful for projecting future emissions and analyzing compliance with regulatory commitments. We use atmospheric measurements of these gases and engineering studies to derive emission factors and scenarios for each of the major anthropogenic sources (leakage from electrical equipment, magnesium casting, aluminum smelting and semiconductor fabrication). Our model is useful for policy analysis because it divides the world into regions of nations that correspond with the political coalitions that dominate the international negotiations through which regulatory commitments are adopted. We show that although firms in many industrialized countries are already limiting emissions, without further policy intervention global emissions will rise 150% (CF4 and C2F6) and 210% (SF6) between 1990 to 2050; radiative forcing will increase 0.026 W m-2. Full application of available low- and negative-cost policies in industrialized nations would cut that radiative forcing by one-quarter. We also quantify plausible future manipulations to governmental data and show their possible effect on compliance with the targets of the Kyoto Protocol. West European nations can "cut" their emissions of these gases by half by 2010 simply by manipulating emission factors within the current bounds of uncertainty. The need for more complete and transparent data on these gases is urgent.