California is launching a first-of-its-kind statewide network of monitors to track greenhouse gas emissions closer to their sources.
Knowing those levels will be a crucial step toward implementing a state law, known as AB 32, that requires California to cut its emissions 25% by 2020.
To start the project, the California Air Resources Board (CARB) bought seven portable analyzers. Six will be placed throughout the Central Valley this year, and one will go in the Los Angeles basin. The analyzers, made by the Silicon Valley company Picarro, are meant to be located far enough apart to cover the state geographically, but close enough together so their measurements overlap.
To the data those analyzers collect, CARB will add measurements from monitoring stations already in place, under the auspices of other agencies, along the California coast.
All the monitors will be gathering data where the most human activity takes place — that’s precisely what makes this project unique. Many stations in remote locations throughout the world are already measuring the global background levels of various greenhouse gases, which is extremely important, says Jorn Herner, manager of Greenhouse Gas Technology & Field Testing for CARB. But this is the first network dense enough to allow scientists to look at small perturbations that tell them where emissions are coming from.
Herner doesn’t expect to be able to pinpoint individual emitters’ numbers, and just how precise the tracking capabilities will be remains to be seen once the network is up and running. But, in combination with a computer simulation model currently being developed, he hopes they will be able to create a gridded inventory of the state’s emissions — where they are occurring and their strength. He calls this a top-down approach, compared to the bottom-up method in which known sources’ estimated emissions are added together for an aggregate, or inventory.
To start, scientists will focus on methane. It’s the second-most important greenhouse gas, it can be measured easily and accurately, and there’s considerable uncertainty in the magnitude of emissions sources, all of which makes it an attractive place for the project to begin.
“If this takes off and brings value to the state in our emission reduction programs, we hope to expand to other gases we’d measure,” Herner says.
The analyzers do measure carbon dioxide, but even though CO2 is the main greenhouse gas related to human activity, it’s further down on the scientists’ list. “CO2 is difficult to model because there’s a lot of sources and sinks that are not well understood,” Herner says. And, he points out, CO2 already has a second data point through the sales figures of fossil fuels: Models can take the amount of methane produced by burning fossil fuels and multiply it by the amount sold.
The first task of the new network will be to see if actual concentrations of methane match the estimates that the models generate.
“The science of finding greenhouse gas inventories is relatively new, and it’s not going to be perfect,” Herner says.
A 2007 study by CARB scientists found that their models may indeed still need some adjustments: Methane measurements from outside Los Angeles exceeded what was expected. “It looks like, if you compare the top-down method with the bottom-up inventory, the current inventory for methane was underestimated by 25%,” Herner says. “Either the inventory apportions statewide emissions in a non-perfect way, or overall emissions estimates are too low.”
He hopes the project will find some of those answers. Most inventories currently in use were developed using the methodology suggested by the UN's Intergovernmental Panel on Climate Change. Because their guidelines must be applicable for the entire world, they become generic, and that might be a problem. “Maybe they have to be modified for specific locations,” Herner says. “We hope to be able to say something about that with this network.”
Of course, there is tremendous interest in figuring out how to measure emissions accurately — an issue that became a stumbling block at negotiations last December in Copenhagen — so the CARB project will be closely watched around the world.
As far as the ultimate uses of the data collected in California, Herner says that remains to be seen. At this point, the project is a research concept.
“We’ll see how robust and accurate the results are, then decision-makers will decide what to do with it,” he says.
Herner predicts that preliminary data will start coming in by summer 2011.