Measuring the greenhouse gas emissions from a city, state, or country requires comprehensive tabulations of energy use, land-use changes, industrial emissions and many other factors.

The National Aeronautics and Space Administration (NASA) has recently explored new methods for managing carbon emissions inventories.  Using NASA’s  Terra satellite, the agency surveyed the “greenness”of California’s vegetation and then plugged the results into anecosystem simulation model to estimate monthly variations in theaccumulated biomass of wood and other plant materials.  One keylimitation for the method: it relied on inventory data from theCalifornia Energy Commission to model the greenhouse gas emissions fromfossil fuel combustion and from agricultural lands throughout the state.

The study found that in 2004, the state’s natural ecosystemsabsorbed as much carbon dioxide from the atmosphere as was emitted byburning fossil fuels, with significant amounts of carbon dioxide beingtrapped in forests and soils during periods of above-normal rainfall.The bad news for California is that such periods of above-normalrainfall have become rare, as the state has been suffering underdrought conditions since the fall of 2006.

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