KYOTO PROTOCOL: multi-gas approach would reduce costs by 60%

A strategy for controlling multiple gases associated with greenhouse warming could reduce control costs by over 60 percent compared with controlling carbon dioxide (CO2) alone, according to a study by the Massachusetts Institute of Technology published in Nature this week.

The study also indicates “flaws in the yardstick” by which gases are compared under the Kyoto Protocol.” The main finding is that including gases other than CO2 emissions from fossil fuels could greatly reduce costs of meeting the Protocol,” observes Dr. John Reilly, lead author of the paper and associate director for research at the MIT Joint Program on the Science and Policy of Global Change. “Economically efficient policies will be required that encourage reduction of these emissions — not an easy task, as reductions must come from sources as diverse as landfills, aluminum production, livestock, and electrical switchgear.”

Much current analysis and policy discussion narrows climate issues to a debate about carbon emissions from fossil fuels. Most economic analyses likewise have considered only emissions of CO2 from fossil fuels. This situation has, according to the present study, led to an approximately 21 percent overestimation of annual costs in 2010 for meeting Kyoto Protocol emissions caps in industrialised regions.

This study analyses climate policy as negotiated under the Kyoto Agreement, including critical issues like forest “sinks” and non-CO2 greenhouse gases. It also explicitly considers atmospheric interactions among these gases, climate feedbacks, the roles of carbon monoxide and nitrogen oxides (key components of smog), and aerosols’ cooling effect.

The study shows that inclusion of non-CO2 gases in the Kyoto Protocol leads to greater reductions in the impact of greenhouse gas emissions than if only CO2 had been included. Achieving approximately the same reduction in warming by controlling fossil CO2 only could cost over 60 percent more than an effort controlling other gases as well. Failure to consider non-CO2 greenhouse gases and sinks also has differential regional effects that could affect the pattern of emissions trading.

The Nature study also notes flaws in the yardstick used to compare greenhouse gases under the Kyoto Protocol. The protocol calls for reductions in emissions of several radiative (Earth-warming) gases to be credited against a CO2-equivalent emissions “cap.” This cap is calculated in terms of Global Warming Potential (GWP), an index defining the contribution of each greenhouse gas to atmospheric warming relative to CO2.

The Nature article shows, however, that use of GWPs as applied in the Kyoto Protocol mitigates climate change considerably more for multi-gas strategies than for supposedly equivalent CO2-only control when emissions cuts are deep enough to stabilise the radiative effects of these gases. “This result,” according to Professor Prinn, “indicates significant weakness in the whole GWP approach, in that this approach does not ‘level the playing field’ for all possible strategies. Instead, an integrated systems approach appears necessary.”

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