METHANE has always been the joker in the greenhouse pack. Cows expel it,
deforesters and rice farmers dump it into the air and landfills can free it in
explosive quantities. But because the sources are so diffuse, methane never
quite seems the threat to the world鈥檚 climate that carbon dioxide does. This is
starting to look like a mistake. CO2 remains the number one cause of
global warming. But methane is not far behind. And, as we report this week
(see 鈥淐ap a landfill鈥攕ave the planet鈥�),
a little-known rule in the Kyoto Protocol is underplaying methane鈥檚
significance.
The problem is that methane lasts in the air only about a decade. But while
it鈥檚 there it acts as a potent warming agent. CO2 acts more gently, but
lingers for a century or more. The protocol鈥檚 emissions targets lump all
greenhouse gases together and assess their relative warming effects over a
century鈥攁 timescale that hides the short-term impact of methane. In
essence, it assumes that we only need to worry about the climate in a century鈥檚
time, not tomorrow.
It would be crazy to dismantle the protocol. But with global warming
apparently accelerating, it鈥檚 time to think about the short term, perhaps by
adding a methane target in the next negotiating round. Meanwhile, nations such
as Britain, which claim they can meet their Kyoto quotas with room to spare,
should target methane now. Otherwise the joker could have the last laugh.
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