This video helps explain how researchers keep track of whether or not California is meeting standards set by AB-32—the 2006 law that mandates a 25% reduction in greenhouse gas emissions by 2020. Scientists monitor emissions round-the-clock via towers in San Francisco and Walnut Grove, California.
Using meteorological data and computer models, the scientists trace the journey of gases collected at the towers back to the areas where the gases originated. They then estimate how much greenhouse gas comes from broad sectors of central California, even from areas that are many miles upwind of the tower. Their probability-based calculations often match existing inventories of greenhouse gas emissions. Scientists have a good handle on the major greenhouse gas culprits in a region — such as the methane emitted by a landfill or livestock feed lot — thanks to models that utilize economic data and other information that indicate a facility's day-to-day operations, pollution and all.
But to get a closer view, researchers recently took their measurement instruments on a flight over Sacramento and the Bay area.