IT took more than four months, but finally they succeeded. The company that owned the world's biggest methane leak, Southern California Gas, has finally repaired a fractured pipe, 8,000 feet down, to stop this climate changing gas escaping into the atmosphere.

It had been stored in an empty abandoned oil reservoir, and because of the delayed repair over 100,000 tonnes of methane escaped, the equivalent of the annual CO2 emissions from 600,000 cars. While age and slack regulation are partially responsible, it does question the technical suitability of such storage, and it's a lesson that those hoping to store captured CO2 in the depleted oil reservoirs under the North Sea might ponder

Leaking methane is the norm from most storage sites, and it's particularly serious with the recent rash of fracking in the USA, and the promise of it in north Yorkshire. There are considerably more than a million small fracking well heads in the US alone, and they all leak methane, up to 12 percent each in Utah, and at least half that amount elsewhere.

It's likely that this goes some way to explain the increasing volume of methane in the atmosphere at the moment, up six percent annually, so doubling every twelve years, and it's certainly making it difficult to reduce the effect on the climate. Not only is it a much more effective gas in preventing heat escaping than CO2 but after a dozen years or so it decays into it, and so is still a serious climate changing gas for decades and centuries to come.

All this is serious enough but other human activities also produce prodigious amounts of methane incidental to their main purpose. Most folk don't realise the amount produced by growing our food, and with another billion hungry folk every fifteen years or so this is going to be difficult to stop.

Rice is the staple food for millions of people and it produces methane while it's flooded. It won't help that the yield falls with a rise in temperature, so for every one degree warmer at night the yield drops by a tenth, just at a time when we need more.

And then there's the methane burped out by cattle, up to 400 litres each daily, from over a billion animals, as well as smaller amounts from sheep, goats, pigs, termites as well as landfill sites.

It gets even more serious when we consider all the methane currently frozen in the sea bed in the Arctic and the surrounding tundra soils and wetlands that has begun to escape as the temperature rises with climate change.

If we needed a reason not to frack, or eat meat, it's spelt methane.