Atmospheric Methane Levels Flatten

Nov. 28, 2006 — Methane, the second-most prominent greenhouse gas, is leveling off in Earth's atmosphere, say scientists.

Concentrations of the gas rose from 1978 throughout the 1980s — with fits and starts and occasional reversals in the 1990s — followed by a flattening out from late 1998 on.

That stabilization is probably from better leak stoppage at oil and natural gas (aka methane) wells, say researchers. Other major sources of methane are cattle, swamps, coal mining, rice paddies, wildfires, biomass burning and termites. At natural gas and oil wellheads, however, it has become both technologically simple and profitable to stop leaks.

"There hasn't been any international campaign to do something about methane," said F. Sherwood Rowland, an atmospheric scientist and Nobel laureate at the University of California at Irvine. "If you start to pay attention (to wellhead leaks), and if it doesn't leak the gas, you can sell it."

Rowland is the lead author on the paper announcing the methane leveling off in the latest issue of Geophysical Research Letters. He was also involved in international efforts to ban manmade chlorofluorocarbons (CFCs), chemicals blamed for the seasonal annihilation of ozone layers over Earth's polar regions.

The methane change is good news with regards to global warming, because methane is 20 times better at heating things up than carbon dioxide, the most abundant greenhouse gas, Rowland told Discovery News. At the same time, however, carbon dioxide continues to mount at an alarmingly accelerated rate.

And that's not the only bad news. Some aren't sure Rowland's observations aren't anything more than a pause in rising methane levels, said Ed Dlugokencky, a methane expert and climate modeler for the U.S. National Oceanic and Atmospheric Administration.

"There's not much understanding of what caused this methane stabilization," said Dlugokencky.

One possibility is that the flattening of methane levels could be caused by the large drop in fossil fuel extraction and animal production in Russia that followed the demise of the Soviet Union.

If that's true, the rise in beef production and oil, gas and coal extraction for China and other booming Asian economies could quickly release the brakes on methane and it will start rising again soon, he said.

"None of us can predict what's going to happen in the future," said Dlugokencky.