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Focus on methane to save the planet

February 13, 2002

SMALL print in the Kyoto Protocol threatens to make global warming more severe than it need be over the next 10 years or so. An obscure rule is discouraging countries from applying cheap technologies that could dramatically curb global warming in the short term, warns a British climate scientist.
        Measures as simple as fixing leaky gas pipes or capping landfill sites could cut emissions of methane, a powerful and fast-acting greenhouse gas, says Euan Nisbet of Royal Holloway, University of London. But the protocol`s rules mean nations will get little reward for such work, compared to the often more expensive efforts to cut carbon dioxide. "Cutting CO2 emissions is essential," he says. "But we have neglected methane and the near-term benefits it could bring."
        The Kyoto Protocol, finalised in Marrakech in November, covers six greenhouse gases released by human activity, including CO2, methane, nitrous oxide and hydrofluorocarbons. Each gas has a different warming potency and a different lifetime in the atmosphere. Under the protocol, a "hundred-year rule" is used to calculate their effect on greenhouse warming: that is, the protocol tots up their warming potential over 100 years.
        This increases the emphasis on carbon dioxide, which stays in the atmosphere for about a century, and downgrades the significance of methane. Methane is the second most important greenhouse gas, but it largely disappears after about a decade.
        Releasing 10 kilograms of methane into the air today will warm the world about as much over the next decade as a tonne of CO2. But because so much of the gas disappears, its warming potency over 100 years is only a fifth that of CO2. It`s the latter figure that has been used to draw up Kyoto emissions targets.
        The effect of the hundred-year rule, Nisbet told a climate conference at Green College, Oxford, last week, is to give a low priority to cutting methane emissions, even though such efforts are often cheaper and would certainly have a bigger short-term impact.
        His warning comes at a time of growing concern about the short-term impact of climate change. Climatologists such as Richard Alley of Penn State University fear that the more the climate is forced to change, the more likely it is to hit some unforeseen threshold that can trigger sudden changes in weather patterns (New Scientist, 2 February, p 18).
        Some climate scientists are reluctant to raise the issue of methane, as they fear it will give ammunition to opponents of the Kyoto Protocol. But others are backing Nisbet`s call. "It makes a lot of sense to try to reduce non-CO2 gases such as methane because, in some ways, it`s easier," says Jim Hansen of NASA Goddard Institute for Space Studies, one of the first scientists to call for global action on the greenhouse effect.
        Nisbet thinks the Kyoto rules should be changed. "Adoption of a 20-year time horizon would substantially increase incentives for reducing methane," he told the meeting. Analysts say it is probably too late to "move the goalposts" for the first Kyoto target date of 2010. But it will make sense to do it for the next date, 2015.
        Countries such as Britain that have promised to go beyond their formal target should be encouraged to make extra efforts to tackle methane, says Nisbet. Over the next 20 years, methane emissions from rotting organic matter in British landfill sites are likely to cause as much warming as half of all the country`s transport emissions, he calculates.
        He also believes that a greenhouse policy built around cost-effective methods of methane control, such as plugging leaks in gas pipes, could prove attractive to the US government, which has set its face against the Kyoto Protocol, claiming it will damage its economy.
        Curbing methane emissions is often cheap and easy, a matter of simply fixing pipes and putting more soil or inert waste on landfills to encourage the growth of methane-eating bacteria, says Nisbet. Yet, in Britain at least, regulations are stacked against such developments. For instance, the financial rules of the gas industry regulators discourage plugging leaks, and environmental taxes penalise the dumping of inert waste on landfills.
        Changing international rules to tackle methane could put pressure on developing countries, which would inevitably have to do more to cut their large emissions from tropical deforestation and draining wetlands. But the overall effect would be worth it, says Nisbet. "I was brought up in a developing country. I know well that they are much more vulnerable to climate change today. They want protection now. They are not prepared to think 100 years ahead, which is what, in effect, the Kyoto Protocol does."

Author: Fred Pearce

New Scientist