Nav: Home

Researchers develop new method to gauge atmosphere's ability to clear methane

June 03, 2019

New research by UMBC's Glenn Wolfe and collaborators is shaping how scientists understand the fate of methane, a potent greenhouse gas, in Earth's atmosphere.

Of the greenhouse gases, methane has the third greatest overall effect on climate after carbon dioxide and water vapor. And the longer it stays in the atmosphere, the more heat it traps. That's why it's essential for climate models to properly represent how long methane lasts before it's broken down. That happens when a methane molecule reacts with a hydroxyl radical---an oxygen atom bound to a hydrogen atom, represented as OH---in a process called oxidation. Hydroxyl radicals also destroy other hazardous air pollutants.

"OH is really the most central oxidizing agent in the lower atmosphere. It controls the lifetime of nearly every reactive gas," explains Wolfe, an assistant research professor at UMBC's Joint Center for Earth Systems Technology. However, "globally, we don't have a way to directly measure OH." More than that, it's well understood that current climate models struggle to accurately simulate OH. With existing methods, scientists can infer OH at a coarse scale, but there is scant information on the where, when, and why of variations in OH.

New research published in Proceedings of the National Academy of Sciences and led by Wolfe puts scientists on the path to changing that. Wolfe and colleagues have developed a unique way to infer how global OH concentrations vary over time and in different regions. Better understanding of OH levels can help scientists understand how much of the ups and downs in global methane levels are due to changing emissions, such as from oil and natural gas production or wetlands, versus being caused by changing levels of OH.

A flying laboratory

NASA satellites have been measuring atmospheric formaldehyde concentrations for over 15 years. Wolfe's new research relies on that data, plus new observations collected during NASA's recent Atmospheric Tomography (ATom) mission. ATom has flown four around-the-world circuits, sampling air with the aid of a NASA research aircraft.

This "flying laboratory," as Wolfe describes it, collected data on atmospheric formaldehyde and OH levels that illustrates a remarkably simple relationship between the two gases. This did not surprise the scientists, because formaldehyde is a major byproduct of methane oxidation, but this study provides the first concrete observation of the correlation between formaldehyde and OH. The findings also showed that the formaldehyde concentrations the plane measured are consistent with those measured by the satellites. That will allow Wolfe's team and others to use existing satellite data to infer OH levels throughout most of the atmosphere.

"So the airborne measurements give you a ground truth that that relationship exists," Wolfe says, "and the satellite measurements let you extend that relationship around the whole globe."

Wolfe, however, is the first to acknowledge that the work to improve global models is far from done. The airplane measured OH and formaldehyde levels over the open ocean, where the air chemistry is relatively simple. It would be more complicated over a forest, and even more so over a city.

While the relationship the researchers determined provides a solid baseline, as most of Earth's air does, indeed, float above oceans, more work is needed to see how OH levels differ in more complex environments. Potentially, different data from existing NASA satellites, such as those tracking emissions from urban areas or wildfires, could help.

Wolfe hopes to keep refining this work, which he says is at "the nexus of the chemistry and climate research communities. And they're very interested in getting OH right."

Getting it right

The current study did consider seasonal variations in OH, by analyzing measurements taken in February and August. "The seasonality is one aspect of this study that's important," Wolfe says, "because the latitude where OH is at its maximum moves around." Considering seasonal shifts in OH concentrations, or even multi-year shifts caused by phenomena like El Niño and La Niña, could be one angle to explore when trying to improve global climate models.

Looking further at OH levels on a global scale using satellite data validated by airplane data could also help scientists refine their models. "You can use the spatial variability and the seasonality to understand at the process level what's driving OH, and then ask if the model gets that right or not," Wolfe says. "The idea is to be able to poke at all these features, where we haven't really had any data to do that with before."

This new research is one step in the journey to enhancing our understanding of the global climate, even as it is rapidly changing. More accurately understanding how, for example, cutting methane emissions would affect the climate, and how quickly, could even influence policy decisions.

"It's not perfect. It needs work," Wolfe says. "But the potential is there."

University of Maryland Baltimore County

Related Methane Articles:

Microorganisms reduce methane release from the ocean
Bacteria in the Pacific Ocean remove large amounts of the greenhouse gas methane.
Origin of massive methane reservoir identified
New research provides evidence of the formation and abundance of abiotic methane -- methane formed by chemical reactions that don't involve organic matter -- on Earth and shows how the gases could have a similar origin on other planets and moons, even those no longer home to liquid water.
Methane not released by wind on Mars, experts find
New study rules out wind erosion as the source of methane gas on Mars and moves a step closer to answering the question of whether life exists on other planets.
Unexpected culprit -- wetlands as source of methane
Knowing how emissions are created can help reduce them.
Methane-consuming bacteria could be the future of fuel
Northwestern University researchers have found that the enzyme responsible for the methane-methanol conversion in methanotrophic bacteria catalyzes the reaction at a site that contains just one copper ion.
New measurement method for radioactive methane
The method developed by Juho Karhu in his PhD thesis work is a first step towards creating a precise measuring device.
New key players in the methane cycle
Methane is not only a powerful greenhouse gas, but also a source of energy.
Diffusing the methane bomb: We can still make a difference
The Arctic is warming twice as fast as the rest of the planet, causing the carbon containing permafrost that has been frozen for tens or hundreds of thousands of years to thaw and release methane into the atmosphere, thereby contributing to global warming.
China not 'walking the walk' on methane emissions
In China, regulations to reduce methane emissions from coal mining took full effect in 2010 and required methane to be captured or to be converted into carbon dioxide.
Interpreting new findings of methane on Mars
New data from the Mars Science Laboratory demonstrating the presence of methane presents novel challenges to explain how it was formed and what it suggests about the potential for life to exist or be supported on Mars.
More Methane News and Methane Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.