Aliso Canyon, Methane, and Global Climate: A Conversation with Paul Wennberg

On October 23, 2015, the Aliso Canyon underground storage facility for natural gas in the San Fernando Valley—the fourth largest of its kind in the United States—had one of its wells blow out, leading to a large release of methane. The leak was not fully under control until February 11, 2016. In the interim, residents of nearby neighborhoods were sickened by the odorants added to the gas, thousands of households were displaced, and California's governor declared a state of emergency for the area. The story made international headlines; the BBC's headline, for example, read, "California methane leak 'largest in US history.'"

The leak was indeed large and undoubtedly difficult for the residents of the area. However, Caltech's Paul Wennberg says there is also a bigger picture to keep in mind: enormous methane and carbon dioxide (CO2) emissions occur all the time, with troubling implications for global climate. Wennberg is Caltech's R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering, executive officer for Environmental Science and Engineering, and director of the Ronald and Maxine Linde Center for Global Environmental Science.

We recently sat down with him to talk about methane emissions and how to put the Aliso Canyon event into perspective.

What was your involvement with the Aliso Canyon event?

We have a greenhouse gas remote sensing system here at Caltech that is part of TCCON—the Total Carbon Column Observing Network. The day after the Aliso Canyon leak started, we observed something really weird in the air above Pasadena. There was a large, big plume of methane and ethane gas that came over. We now know that it was from the Aliso Canyon facility. We are providing data for the final analyses of the leak.

In the past you have suggested that the methane emissions from Los Angeles are much larger than was previously included in models.

Right. Thankfully, models are now catching up as we learn more from the data.

What does the Aliso Canyon event suggest about Los Angeles's methane emissions in general?

Aliso Canyon was a very dramatic event. Everyone heard about it worldwide. The leak continued for about 100 days, and yet it only doubled the amount of methane being emitted by LA during that period. This was a tragedy for the people living next to it, who had to deal with horrible nausea and other side effects of the chemicals associated with the natural gas. But from a climate point of view, the methane leak was actually quite trivial.

There are enormous amounts of methane being released into the atmosphere globally as a result of human activity. That is certainly true of LA, but as far as climate goes, it doesn't matter whether it's released in LA or New Zealand. On the timescale that methane sticks around in the atmosphere, it gets well mixed and affects the entire planet.

How much methane is emitted per year?

About three hundred teragrams [Tg; one teragram is equivalent to one billion kilograms] of methane are emitted every year by people and the activities of people, like agriculture and energy. Los Angeles emits about 0.4 Tg. That means that of the human methane emissions, LA as a total is one part in a thousand—not nothing, but a pretty small amount.

For perspective, Aliso Canyon emitted around 0.1 Tg. It was a big event, but what it really illustrates is how big a challenge we truly face. There are many sources emitting methane into the atmosphere and they are very diffuse. Reducing them will require hard work on many, many fronts. So it's not just, "If we solve this one problem, everything will be beautiful in the world."

You could imagine the response to the Aliso Canyon leak might be that we would all of a sudden focus all of our efforts trying to prevent leaks in natural gas storage facilities. That would not be the right answer from a climate perspective.

How should people go about eliminating methane emissions?

There is not "one" fix. Each source requires a different strategy for mitigation.

First, there is fixing leaks in the pipelines and storage facilities.

Then, it turns out that ruminants like cows and sheep produce a lot of methane—probably a third, if not more, of the human emissions. A paper about this, recently in Science, suggests that an important part of the recent increases in methane is coming from agriculture. Depending on what you feed these ruminants, they produce less methane. They eat grass, but they can't metabolize it: they have a fermenter going in their bellies—a whole microbiome that breaks the grass down into smaller things like acetate that they can metabolize. Depending on the microbiome of their guts, the cows and sheep make more or less methane. And it turns out that you can manage this.

Then there are the wetlands used for rice agriculture. Methane is produced anaerobically—in places with no oxygen—by Archaea. If you have a flooded rice paddy, the methane is produced at the roots and is transpired through the rice plants into the atmosphere. Quite a few studies now show that if you can change your rice agricultural practices to allow the fields to dry periodically, the methane emissions drop hugely.

If you were able to fix all of these things what would the impact be in terms of climate change?

If we could really knock the methane emissions back to what they were before people started emitting methane, it would be a large change. It would be a half a watt per meter squared. The total global warming would drop by around 25 percent.

How does the importance of reducing methane emissions compare to the importance of reducing carbon dioxide emissions?

Globally, methane is important. It's maybe a third of the climate forcing of CO2—that is, the increase in methane has contributed about one third of the total change in Earth's climate over the last 100 years. In terms of climate impact, however, the methane emissions from people in Los Angeles are absolutely dwarfed by their CO2 emissions—all of our driving, going on airplanes, and everything else that we do. Still, if we are to reduce our global warming potential and the amount of greenhouse gasses we emit to the atmosphere, methane has to be part of the equation.

We like to think that we can solve these problems by fixing singular events, but climate doesn't work that way. We're talking about the emissions of 7 billion people. If it were that this was produced by 100 events like Aliso Canyon, this would be a simple problem: we solve the 100 problems, and we're done. But it's all of us, and it's all of what we eat, it's all of the energy that we use, it's all of the miles that we drive. It's a much more complex problem.

What work is your group currently doing in terms of methane?

One of the things we've been doing is long-term monitoring. Natural gas is mostly methane (CH4) but there's also ethane (C2H6) in it and this provides a way of separating the signature of methane emitted from agriculture, which has no ethane, and emissions from natural gas, which does.

Over the last five years or so, the production of oil in the United States has increased hugely, and associated with that oil production is natural gas, and therefore methane and ethane. Traditionally, most of the ethane produced at a wellhead was pulled off and sent to the plastic industry. With the changing oil production, the market has become flooded in ethane: there's simply not enough plastic to be made. When the industry can't sell the ethane to the plastic industry, they simply leave it in the natural gas. We see this in the natural gas delivered to Los Angeles. Five years ago natural gas had about 2 percent ethane. Now it's 5 percent—it's more than doubled. What we've seen—and this has nothing to do with Aliso Canyon—is that over the last five years, the amount of ethane in the air over Pasadena has increased.

That's important because it tells us that a significant fraction of the methane that's being released in LA is coming from natural gas brought into Los Angeles. This has been a topic of a lot of debate. Is the big methane emitter the oil production down in the Long Beach area? Is it waste treatment plants? Is it garbage dumps? What we find is that about half of all the methane emitted in this part of LA is gas that originally came in on a pipeline.

How do you know that?

We actually know from the gas company how much ethane is in the natural gas. They report this publically from one of their storage fields and this matches the ethane in samples of the natural gas coming into our buildings.

Are there other projects under way at Caltech to study methane emissions?

Christian Frankenberg [associate professor of environmental science and engineering at Caltech and a JPL research scientist] has been leading an effort to build remote sensing instruments that allow imaging of methane plumes. Using small spectrometers on airplanes, he has flown over areas where you might have a lot of methane emissions and identified individual sources. Last year they were able to find individual pipelines that were leaking in Colorado and in New Mexico. They found several big leaks from pipelines and were able to tell the pipeline operators, who shut them down and fixed them.

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We recently sat down with Paul Wennberg to talk about methane emissions and how to put the Aliso Canyon event into perspective.

Will Orbiting Flying Carpets Light the World?

Imagine a rocket emerging from Earth's atmosphere. Its nose cone opens and out comes a flying carpet.

It had been folded and rolled into a cylinder just 3 feet in diameter and 5 feet long. But freed from the launch vehicle, it unfurls to its full expanse: two-thirds the size of a football field and 1 inch thick.

Now imagine that this is one of 2,500 spaceborne magic carpets flying side-by-side in tight formation, covering an area of 3.5 square miles (9 square kilometers) in Earth orbit. That's 1,670 football fields, still only an inch thick.

What are they doing up there? Capturing the sun's energy and beaming it down to Earth to make electricity.

"What we're proposing, somewhat audaciously, is to develop the technology that would enable one to build the largest-ever-built space structures," said Harry Atwater, one of three Caltech professors leading the Space Solar Power Initiative, or SSPI. The other two are Ali Hajimiri and Sergio Pellegrino, who is also a senior research scientist at NASA's Jet Propulsion Laboratory. "The work I do at Caltech benefits enormously from the things I do at JPL," Pellegrino said, "and from the people at JPL."

Read the full story from JPL News

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For much of the Earth’s population that lacks access to reliable electricity, orbiting solar panels could be a solution.
Monday, May 23, 2016
Brown Gymnasium – Scott Brown Gymnasium

Animal magnetism

Monday, February 29, 2016
Brown Gymnasium – Scott Brown Gymnasium

Animal magnetism

Thursday, May 26, 2016
Avery House – Avery House

The Mentoring Effect: Conference on Mentoring Undergraduate Researchers

Tuesday, April 12, 2016
Center for Student Services 360 (Workshop Space) – Center for Student Services

TA Workshop: Getting the Biggest ‘Bang for Your Buck’ - Teaching strategies for busy TAs

Two Named as National Security Science and Engineering Faculty Fellows

Oscar Bruno and Julia Greer have been named National Security Science and Engineering Faculty Fellows by the Department of Defense (DoD). Fifteen university faculty scientists and engineers comprise the 2016 class of fellows.

"The program awards grants to top-tier researchers from U.S. universities to conduct long-term, unclassified, basic research of strategic importance to the Defense Department," said Melissa L. Flagg, deputy assistant secretary of defense for research at the DoD, in an announcement of the new fellows. "These grants engage outstanding scientists and engineers in the most challenging technical issues facing the department."

Oscar Bruno is a professor of applied and computational mathematics in Caltech's Division of Engineering and Applied Science (EAS). Bruno's work aims to develop high-performance computer software for evaluation of engineering structures and simulation of physical phenomena—including optical devices, communications and remote-sensing/stealth systems, materials-science microstructures and seismic, aerodynamic, and hydrodynamic phenomena. In 1989, Bruno received his PhD, graduating with a Friedrichs Prize for an outstanding dissertation in mathematics from New York University's Courant Institute of Mathematical Sciences. He became an associate professor at Caltech in 1995 and a professor of applied and computational mathematics in 1998. Dr. Bruno is a former member of editorial boards of the Proceedings of the Royal Society of London and the SIAM Journal on Applied Mathematics, and he currently serves in the board of the SIAM Journal on Scientific Computing. He has served as executive officer of Caltech's Applied and Computational Mathematics department, and he is the recipient of a Young Investigator Award from the National Science Foundation and a Sloan Foundation Fellowship. He is member of the council of the Society for Industrial and Applied Mathematics. In 2013, he was named as a fellow of the Society for Industrial and Applied Mathematics.

Julia R. Greer is a professor of materials science, mechanics, and medical engineering in EAS. Her research focuses on creating and studying advanced materials that combine hierarchical architectures and unique nanoscale material properties. Greer received her PhD in materials science from Stanford and did post-doctoral work at the Palo Alto Research Center before joining the Caltech faculty in 2007. Her work was recently featured on CNN's 2020 Visionaries and was recognized among the Top 10 Breakthrough Technologies by the MIT Technology Review in 2015. Greer has received a number of recognitions and awards, including Gilbreth Lectureship by the National Academy of Engineering (2015), Young Global Leader by World Economic Forum (2014), Kavli Early Career Award (2014), Nano Letters Young Investigator Lectureship (2013), Society of Engineering Science Young Investigator (2013), NASA Early Career Faculty (2012), Popular Mechanics Breakthrough Award (2012), DOE Early Career (2011), DARPA's Young Faculty (2009), Technology Review's TR-35, (2008). Greer serves as an Associated Editor of the journals Nano Letters and Extreme Mechanics Letters.

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Oscar Bruno and Julia Greer have been named National Security Science and Engineering Faculty Fellows by the Department of Defense.

Living—and Giving—the Caltech Dream

Growing up in Tehran, Iran, Mory Gharib (PhD '83) attended large, crowded schools. He was the kid who always raised his hand in class and asked tough questions. He craved one-on-one time with his teachers, which seldom came to pass.

So when the young Gharib read a newspaper article about a school in California with a three-to-one student-faculty ratio, it seemed almost unimaginable. Over the years, though, that school—Caltech—remained in his thoughts.

Years later, Gharib finally made it to Caltech as a graduate student. Since that time, he has built a distinguished career as a  researcher, mentor, inventor, entrepreneur, leader, and benefactor. And he has continued to search for the answers to tough questions.

"I couldn't have done this anywhere else," he says, referring to his career. "Caltech took care of me, and I have to take care of it."

In appreciation for the opportunities Caltech afforded him, Gharib—who currently serves as the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering, director of Caltech's Graduate Aerospace Laboratories, and vice provost—has created an endowed fellowship fund to support new generations of Caltech graduate students.

Read the full story on the Caltech Giving website.

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In appreciation for the opportunities Caltech afforded him, Mory Gharib is supporting future graduate students through an endowed fellowship fund.
Monday, March 28, 2016 to Friday, April 15, 2016
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Spring TA Training -- 2016

Professor Rosakis Receives the Von Kármán Medal

Ares Rosakis, the Theodore von Kármán Professor of Aeronautics and Mechanical Engineering in the Division of Engineering and Applied Science, will receive the Theodore von Kármán Medal from the American Society of Civil Engineers. The medal was established and endowed in 1960 by the Engineering Mechanics Division of the society—now the Engineering Mechanics Institute (EMI)—in order to recognize distinguished achievement in engineering mechanics. The Von Kármán medal is the flagship medal of the EMI.

Rosakis is being honored for "discovering several fundamental physical phenomena in dynamic fracture of heterogeneous materials and interfaces at various length and time scales," according to the award citation. Particularly noted was his proposal of the concept of "laboratory earthquakes" and the associated unique experimental facility, which was established at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT) more than a decade ago. Through experiments that reproduce the basic physics of earthquake rupture, he and his collaborators, including Caltech seismologist Hiroo Kanamori, were able to experimentally show that earthquake ruptures may propagate with "super-shear speeds"—speeds in excess of the bulk shear wave speeds of the surrounding material. They also conclusively proved that certain historic, large earthquakes did transition to super-shear and explained the unusual ground-shaking signatures that are characteristic of such catastrophic events.

"I feel extremely honored and humbled to receive the Theodore von Kármán Medal from the American Society of Civil Engineers," says Rosakis. "I am especially thrilled to receive an award bearing the name of von Kármán, whose remarkable achievements epitomize Caltech's natural interdisciplinary approach to science and engineering."

Rosakis has also served as the fifth director of GALCIT, which was established and directed by Theodore von Kármán in the early 1920s.

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Ares Rosakis has been selected to receive the Theodore von Kármán Medal from the American Society of Civil Engineers.

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