A multi-gas control strategy that includes abatement of all greenhouse gases and sink enhancement significantly reduces the cost of the Kyoto Protocol Most discussion of how to address global warming has focused on one single greenhouse gas (GHG), carbon dioxide, from fossil fuel use only. Yet, other GHGs and carbon sinks also affect the atmosphere's "radiative budget." The Kyoto Protocol allows credit for enhancing sinks and reducing five classes of other greenhouse gases-methane, nitrous oxide, perfluorocarbons, hydrofluoro-carbons, and sulfur hexafluoride-in a multigas emissions limit. Several studies at MIT address the cost implications of the Kyoto Protocol's multigas approach.