Multi-gas assessment of the Kyoto Protocol

The Kyoto Protocol allows reductions in emissions of several 'greenhouse' g ases to be credited against a CO2-equivalent emissions limit, calculated us ing 'global warming potential' indices for each gas, Using an integrated gl obal-systems model, it is shown that a multi-gas control strategy could gre atly reduce the costs of fulfilling the Kyoto Protocol compared with a CO2- only strategy. Extending the Kyoto Protocol to 2100 without more severe emi ssions reductions shows little difference between the two strategies in cli mate and ecosystem effects. Under a more stringent emissions policy, the us e of global warming potentials as applied in the Kyoto Protocol leads to co nsiderably more mitigation of climate change for multi-gas strategies than for the-supposedly equivalent-CO2-only control, thus emphasizing the limits of global warming potentials as a tool for political decisions.