STEVE INSKEEP, HOST:
We have a story now about the effort to measure progress against climate change. Cities around the world are responsible for the vast majority of planet-warming gas emissions, but they have some trouble estimating just how much they produce. Many American municipalities estimate their emissions, but the estimates are published just once a year, and researchers find they may be too low. Which is why scientists at the University of California, Berkeley, are pitching a new way to track these emissions using sensors in real time. Here's Kevin Stark from KQED.
KEVIN STARK, BYLINE: I'm assuming - are we going up this ladder here?
NAOMI ASIMOW: We're going up this ladder, yeah.
STARK: Here, you go first.
I'm climbing onto the roof of a research building near UC Berkeley's campus with Naomi Asimow. She's a graduate student studying climate change, which is mainly driven by carbon dioxide from human activity.
ASIMOW: Our job as researchers is to figure out where that CO2 is coming from.
STARK: It's invisible to the naked eye, but detectable in concentration by sensors like the one right here. Asimow points to a white cylinder. It's the size of a small thermos.
All right, wow. Look at this in here. So tell me about what's inside here.
ASIMOW: A little mini circuit board, and it has an SD card in it that's collecting the data.
STARK: In order to meet its climate goals, the U.S. uses expensive research towers to provide a zoomed-out national picture of CO2 emissions. But cities also need more specific information to know if they're meeting their individual climate goals. Right now, oil refineries, for example, or other industrial facilities, report how much fuel they use to regulators, who then calculate their emissions based on the average of what would be contained in a gallon of gasoline. Asimow says her sensors could be useful to cities by providing constant granular feedback that may be more accurate.
ASIMOW: My dream is that there's a ground-based network like this in every city and that cities can reliably quantify their emissions.
STARK: Cities could place these sensors downwind of one of those refineries to monitor if the emissions are as expected. This way, they could see if a company under-reports, or if equipment is leaching greenhouse gas into the atmosphere that would otherwise be missed. Many cities already use sensors to track different kinds of pollution, like smog. Daniel Hamilton is Oakland's sustainability director.
DANIEL HAMILTON: Getting these sensors in place in as many places as possible will help us identify where the hot spots are so that we can take action.
STARK: He says the impacts can vary down to the block level. Cities could use the CO2 sensors in a similar way.
HAMILTON: Sensors have a huge role to play in this because we're understanding more that localized impacts are really important in terms of setting policy.
STARK: But air regulators point out that they aren't perfect. David Ridley studies emerging technology for the California Air Resources Board. He says they can be imprecise, although...
DAVID RIDLEY: There's strength in numbers that you can deploy 50-plus of these sensors across a wider area, and then if you've got careful calibration and quality control, you can start to then see patterns.
STARK: If regulators place the sensors along highways, for example, and they find CO2 concentrations are consistently higher than they expect, then they know their estimates are wrong. That could lead to a better understanding of their carbon footprint. Los Angeles, Providence, R.I., and Glasgow, Scotland, are using Berkeley's network, and the White House says they want to adopt these kinds of sensors as part of a national monitoring system.
For NPR News, I'm Kevin Stark in San Francisco. Transcript provided by NPR, Copyright NPR.
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