[caption id="attachment_64743" align="alignright" width="300"] Emissions of greenhouse gasses in Sonoma County in 2011 (credit: Climate Protection Campaign; click to enlarge)[/caption]

SANTA ROSA -- Greenhouse-gas emissions have continued a three-year downward trend in Sonoma County, primarily reduced by fewer vehicle trips in a slowed economy and a greater supply of renewable energy, according to a report released today.

The annual report, produced by the Santa Rosa-based nonprofit Climate Protection Campaign, found that the 3.79 million metric tons of carbon dioxide emitted from transportation, natural gas, electricity and solid waste last year represented a 14 percent reduction in emissions countywide in 2008--2011.

However, further reductions will be necessary to hit a self-imposed countywide annual emissions limit of 2.7 million metric tons of carbon dioxide by 2015, particularly if the North Bay economy continues to improve, according to Ann Hancock, executive director of the organization.

"The decrease, a lot of it is attributable to economic contraction," she said. "The question is, how do we get those levels to go down for the right reasons?"

The most significant decrease was in emissions related to electricity use, currently 11 percent of the county's overall emissions profile. Levels fell 91.7 percent from 2008 to the equivalent of 496,000 metric tons of carbon dioxide. A 16 percent reduction in demand during the period helped drive that decrease, due mostly to reductions in recession-hit commercial and industrial sectors.

In addition, the volume of greenhouse-gas emissions created per megawatt-hour fell 40 percent for the period, due to a rise in hydroelectric generation productivity, zero-emission sources and low-emission natural gas power plants.

Emissions from transportation, which accounts for 60 percent of overall greenhouse gases in Sonoma County, have fallen 3.9 percent to 2.54 million tons since a recent peak in 2009.

Natural gas emissions declined 8.6 percent to 677,000 tons, compared with those of 2007. Solid-waste-connected emissions of 79,000 tons were 26 percent lower than in 2007.

Agricultural emissions were added to the annual study in 2010 and are not considered towards the emissions-reduction target. Only livestock-related sources of methane and nitrous oxide were measured. Those emissions fell to 434,000 tons, a decrease of 6.9 percent.

Continuing the downward trend in an improving economy could hinge significantly on the implementation of Sonoma Clean Power, a proposed renewable energy--focused power agency in Sonoma County, according to Ms. Hancock.

"We think that Sonoma Clean Power is one of the most powerful ways to achieve that goal," she said.

The Climate Protection Campaign has published the annual report since 2008, beginning with data from 2007 as part of the countywide Climate Action Plan. The report uses available data and analytical models to estimate emissions from a number of sources, using the same methods year-over-year to provide a consistent benchmark.