Royal Holloway, University of London, UK

Methane humour hides serious issues, argues a geologist.

Methane people are like the Jumblies of Edward Lear's poem — far and few, far and few. We work together across continents, sharing air samples in 'round robin' experiments. We also suffer bovine eructation jokes; but it's not just about cows' breath.

Methane is a potent greenhouse gas, produced by wetlands, fossil fuels, grass and forest fires, and rice paddies. But there are major puzzles in the global budget. Methanologists at a recent meeting in Cape Town, South Africa, discussed two of these.

One stems from experiments suggesting that plants emit methane (F. Keppler et al. Nature 439, 187–191; 2006). Our first reaction was 'surely not!', yet satellite studies of tropical forests seem to back up the result. We folk who once energetically sampled the atmosphere on mountain peaks are becoming plant biochemists, watching air bubble through flasks.

Another dispute surrounds methane leaks from fossil fuels. We used to estimate leakage by measuring the carbon-14 in methane. But nuclear power stations release this, so the technique became useless.

Recently, researchers reanalysed methane's carbon-14 record in a way that avoids the nuclear problem (K. Lassey et al. Atmos. Chem. Phys. Disc. 6, 5039–5056; 2006). The result is surprising: roughly 29% of atmospheric methane is fossil — much more than expected. Some of this leakage is geological (that's a worrying puzzle too), but most is from gas and coal industries.

Methane is the quickest, cheapest, easiest greenhouse-gas target. But governments aren't interested. Important monitoring programmes were cut recently in Europe and Australia, and UK regulators even limit industry proposals for leak reduction. Are we looking a gift cow in the mouth?