Californians concerned about man-made carbon dioxide emissions have a new tool for directing that concern toward the mirror. The California Air Resources Board (ARB), along with partner organizations, created CoolCalifornia.org, a new Web portal enabling citizens to calculate their own carbon footprints.

Many organizations offer online calculators for individual aspects of consumption, such as electricity or water usage. CoolCalifornia.org is the first California Web calculator to combine all major aspects of citizens' consumption, enabling them to determine their entire carbon footprints, said Ken Bowers, air pollution specialist for the ARB.

Users enter information into the calculator about their spending on electricity, water, sewage, gasoline, food, clothing, furniture and various other personal consumption categories. CoolCalifornia.org then analyzes the carbon-producing activities involved in producing and delivering those goods or services. Bowers calls many of those factors "indirect" carbon emissions, which may be less obvious than "direct" emission sources.

"With gasoline, the direct emissions come out of the tailpipe, but there is a certain amount of indirect emissions associated with gasoline -- producing it from the well, transporting it and getting it to the pump," Bowers said.

Do you ever consider the carbon impact of your water usage? When Californians enter the amount they spend on water usage, the Web calculator factors in the carbon produced by extracting the water from a reservoir or river, pumping it to a treatment plant to make it drinkable and pumping it through the city to citizens' homes. The portal also itemizes the foods that citizens purchase to calculate the resulting carbon production more accurately, said Bowers.

CoolCalifornia.org went live in February 2008, and the ARB hopes to update the service in September to evaluate carbon footprints with even more detail. For example, the new version will let users specify if they purchase locally produced food, which would lower their carbon footprint scores.

Naturally, incorporating this level of detail into each of the portal's consumption categories requires huge amounts of data. The ARB partners with organizations like the Berkeley Institute of the Environment, the California Energy Commission and others with relevant research already on hand.

Once users enter consumption information, the calculator produces a score and compares the score to that of similar households. The portal also offers suggestions for how users can reduce their carbon footprints.