Studies find different reasons for global methane riddle

August 10, 2011

Two new UC Irvine papers reach markedly different conclusions about why methane, a highly potent greenhouse gas, unexpectedly leveled off near the end of the 20th century. They appear today in the journal Nature.

Both note that after decades of increases due to worldwide industry and , the tapering off of the hazardous in the atmosphere – which began in the 1980s – was remarkable.

"It was an amazing mystery as to why this occurred," said earth system science professor Eric Saltzman, a co-author of one paper, which suggests that reduced use of petroleum and increased capture and commercial use of natural gas were the driving factors.

A second UCI paper found that water efficiency and heavier commercial fertilizer use in the booming Asian farming sector provided less fertile ground for soil microbes that create methane, while at the same time increasing nitrous oxide, another greenhouse gas.

Associate researcher Murat Aydin, lead author on the first paper, drilled into South Pole and Greenland glaciers to extract trapped air as much as a century old. The samples were analyzed for ethane, a chemical that has some of the same sources as methane but is easier to track.

"Levels rose from early in the century until the 1980s, when the trend reverses, with a period of decline over 20 years," Aydin wrote. "We find this variability is primarily driven by changes in emissions from fossil fuels."

The authors posit that replacement of oil with lower-priced natural gas could be key.

The second team measured and analyzed the chemical composition of methane in the from the late 1980s to 2005. They found no evidence of fewer methane atoms linked to fossil fuel. Instead, the sharpest trend by far was changes in the Northern Hemisphere linked to new farm practices, mainly the use of inorganic fertilizers instead of traditional manure and drainage of fields mid-season.

"Approximately half of the decrease in methane can be explained by reduced emissions from rice agriculture in Asia over the past three decades, associated with increases in fertilizer application and reductions in water use," said lead author Fuu Ming Kai, who wrote his UCI doctoral thesis on the work and is now with the Singapore-MIT Alliance for Research & Technology.

Martin Heimann, director of Germany's Max Planck Institute for Biogeochemistry, was asked by Nature editors to write a commentary on both papers.

"It is indeed very remarkably rare that two differing studies about the same subject come out from the same department – I can't think of a similar case. But I think both analyses are scientifically sound and in themselves consistent," said Heimann, lead author on the Nobel Prize-winning Intergovernmental Panel on Climate Change reports. "At this time I would not favor one over the other."

Heimann has invited members of both teams to a September symposium at which, he said, "we will discuss the two studies from all angles."

Identifying methane sources is urgent. Research has shown that the fast-acting greenhouse gas is the second-largest contributor to climate change. Scientists around the world were heartened by the stabilizing levels, but there are now signs the hydrocarbon may be on the upswing again.

"We will need to reconcile the differences," said earth system science professor James Randerson, a co-author on the second paper. "The important thing is that we must figure out – as scientists and a society – ways to reduce emissions."

Explore further: Canada joins U.S. EPA program

Related Stories

Canada joins U.S. EPA program

July 14, 2005

Canada Thursday became the 16th nation to join the U.S. EPA's Methane to Markets Partnership to reduce emissions of the greenhouse gas methane.

Causes of methane growth revealed

September 9, 2005

Following an international study into how methane levels in the atmosphere have evolved during the past 2000 years, atmospheric scientists have a new insight on methane, one of the world's most influential greenhouse gases.

Measuring methane

March 1, 2011

Methane is an extremely potent greenhouse gas. Wetlands, gas hydrates, permafrost, termites, oceans, freshwater bodies, non-wetland soils, are all natural sources of atmospheric methane; however, the majority of methane presence ...

Recommended for you

Caves in central China show history of natural flood patterns

January 19, 2017

Researchers at the University of Minnesota have found that major flooding and large amounts of precipitation occur on 500-year cycles in central China. These findings shed light on the forecasting of future floods and improve ...


Adjust slider to filter visible comments by rank

Display comments: newest first

2.1 / 5 (10) Aug 10, 2011
That is great news.

The problem is when all those receiving research grants magically reach the same conclusion.

That is the root of the climate scandal and oscillating solar neutrinos.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
1 / 5 (2) Aug 10, 2011
The only big methane production phenomenon starting in 2000 was the Bush administration - both personally and from two illegal wars that drove up fossil fuel usage by the largest fossil fuel consumer on the planet - the US military. Ah, the GW Bush administration and the stupid people that supported it, and the Obama administration that continues GW's idiot neo-con policies - the negative gift that just keeps on giving and the methane isn't the worst of it. These idiots destroyed our economy as well - and continue to.
not rated yet Aug 10, 2011
More evidence of the soft nature of climate science in general. Two studies that reach very different conclusion as to the source of methane and their reductions.

What neither study found was a replacement for phosphate in the chemical fertilizers - NPK. If current estimations on phosphate resources are correct and we have less than a 100 years before it's completely exhausted - gone,



we'll be up to our necks in chaos caused by starvation and food riots - and climate change will seem like a luxury problem to have.
5 / 5 (1) Aug 10, 2011
No Dug, we'll just go back to cowsh*t.....
not rated yet Aug 12, 2011

In 100 years we'll all be Borg, and our nutrition will be obtained via an electrical plug... (I'm only half-joking)

Jokes aside, if the rise in food prices as a result of nutrient scarcity and/or ever-expanding population is gradual (ignoring short-term swings), then over time people might just start having fewer children (due to expense of feeding them), and the global population may start to decline. Hard to project these things 100 years into the future, but that's enough time for several generations to come and go.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.