"The L.A. Basin is very geologically active," says Sander. "You've probably heard of the La Brea Tar Pits? That's an area where there are a lot of organisms that anaerobically produce methane." Methane escaping through these ground seeps is one theory, anyway. Sander also suspects the labyrinthine network of tubes that ferries natural gas through town. "There are millions of miles of little pipes that go from distribution stations to people's houses," he says. A lot of them leak, and "the leaks can be very substantial."
Emissions of questionable origin are called fugitive emissions, and they account for a decent-sized hunk of any city's overall greenhouse-gas output. L.A. officials estimate that the city's yearly carbon footprint weighs 39 million tons, with this breakdown: 43 percent vehicle emissions, 21 percent commercial buildings, 19 percent municipal energy use, 16 percent "industrial fugitive or other," and 1 percent wastewater.
That 16 percent is a little fuzzy because, again, emitters are judging their output using models. "That's the best they can do," Duren says. "Then we might come along with atmospheric measurements and go, ‘Oh, actually you're underestimating it by a factor of two.'"
Behind the CLARS facility is a rattling, wheezing shed that houses a Picarro, an air-sampling device that displays real-time readings of ambient gases. Sander looks concerned over a sudden spike in CO2 on the machine's monitor, then realizes it's simply us, exhaling.
This is another component of Megacities' full-court press: a network of a dozen or so Picarros going up this year in different L.A. neighborhoods, where they will ceaselessly inspect the air for greenhouse gas. A planned satellite component adds another layer of detection.
Only one spacecraft in orbit right now is monitoring greenhouse gases, Japan's Gosat (Greenhouse Gases Observing Satellite), and its resolution isn't good enough to give an accurate picture of a city's emissions. But in the next few years, NASA plans to launch the Orbiting Carbon Observatory (OCO-2) satellite and install a new instrument (OCO-3) on the International Space Station. Both devices will periodically take snapshots of the "chemical weather" over population centers. "OCO-3 will have a ‘city mode' where it rapidly starts sweeping back and forth like a whisk broom," says Duren. He expects the satellite to take some 3,000 samples over a city in just a few seconds.
A Picarro sampler sniffs the air on Mount Wilson for C02, methane and other potent climate-altering emissions. It's one of many Picarros going up around Los Angeles as part of the Megacities ground-based climate science network. John Metcalfe
With this bulging grab bag of equipment, the Megacities team hopes to sculpt a model of L.A.'s emissions so detailed that they'll be able to pull out individual signatures, such as exactly what and how much is spewing from rush-hour traffic or the port system or large landfills. Once they get an emissions baseline for Los Angeles, they hope to assist other cities in starting their own climate-reading networks.
Duren's team is already coordinating with French scientists running a Megacities sister project in Paris. (Researchers had to move a Picarro on the Eiffel Tower because its readings were skewed by steamy tourist lung vapors.) The Americans are also trying to link up with a third group in São Paulo, Brazil, which has long battled heavy air pollution.
The idea is to prepare a set of climate archetypes that can be applied to different megacities. The L.A. area is on the ocean, ringed by mountains, and often holds emissions in place like a lidded bowl. Perhaps what the Megacities team learns about emissions here will also apply in Mumbai, India, which has a similar geography. In contrast, Paris' layout makes emissions rise in a wind-blown plume.
"The idea for the project is, we pick a representative number of cities that are these different archetypes," says Duren, "and if we can characterize them with this giant laboratory, if you will... you've got a system that you can apply with confidence, everywhere."
To what end, ultimately?
The goal is to one day have a comprehensive network for sensing greenhouse gases in all the major cities across America or even the world. With that in place, an obvious application would be capping sources of fugitive emissions. An eagle-eyed satellite might detect roiling leaks in natural-gas pipes caused by aging infrastructure, or disasters like hurricanes and earthquakes. Then cities could prioritize repair crews accordingly.
If the researchers can extract the signature of freeway traffic, it could instruct a municipality how and where to build future roads, enact tolls, or allot carpool lanes. It could also alter the dialogue of commuting: If you reside in the suburbs but drive through a city every day to work, are you somehow on the hook financially or morally for spewing fumes into the greater urban cloud? That issue matters in Los Angeles, where regional commuters arguably bear environmental responsibilities "even if they don't live in L.A.," says Pascual of the mayor's office.
As the outlines of our individual footprints become clearer, perhaps the Megacities legacy could even motivate some of us to pull the old bike out of storage instead of reaching for the car keys.
"I guess people are aware that when they use their cars, there's something coming out of the exhaust pipes. But because they can't see it, they don't really have a feeling for how much is coming out," says Scripps' Keeling. "That's created a bit of complacency."
This essay appears in the ebook "City 2.0: The Habitat of the Future and How to Get There," co-produced in partnership by The Atlantic Cities and TED Books.