It’s a well-known fact that Governor Schwarzenegger does not fly commercial. And it’s also well-known that he flies a lot.

But when word trickled out today that he intended to try and make amends for all the greenhouse gases his private jet creates, it got some of us wondering– just how big is the governor’s so-called ‘carbon footprint’?

Robert Salladay at the Los Angeles Times had the early story on the governor’s decision to write an annual check to help offset his carbon emissions. Schwarzenegger’s aides will attempt to add up all of those frequent flyer miles, assign a dollar value to them, and then the governor will donate that money to the Pacific Forest Trust. That organization, says the governor’s office, is the “gold standard” when it comes to efforts to ameliorate carbon dioxide emissions. The PFT will apparently use the money to help sustain a 2100 acre redwood forest in Humboldt County.

Those trees, says the governor’s office, will absorb 500,000 tons of CO2 over a 100 year period.

But is that enough?

Using some data provided to us by the Sierra Club… and with the help of a trusty intern and a calculator, the governor’s high-flying travels leave quite a footprint. The Sierra Club estimates that a mid-size Gulfstream jet (similar to what the governor uses) contributes 28 lbs. of carbon per gallon of jet fuel. Using some approximate distances, and published sources of fuel consumption for those jets, you get the following, one-way emissions:

Los Angeles to Sacramento: 5,929 lbs. of CO2
Los Angeles to Washington, DC: 37,849 lbs. of CO2
Los Angeles to Columbus, OH: 32,579 lbs. of CO2
Los Angeles to Honolulu, HI: 42,148 lbs. of CO2

The governor has been known to make two, sometimes three, round-trip flights from his LA home to Sacramento in a week. He was in Washington, DC the past few days. He’s been known to vacation in Hawaii. And he heads to Columbus in a few days for the annual ‘Arnold Classic.’

The math makes the half million tons of CO2 over 100 years absorbed by the trees start to not look so big. Granted, these are only estimates; and the governor’s aides say there are often staffers on the jet with him, so it’s not just his carbon footprint involved.

But environmentalists say planting trees isn’t enough. “I think those that have a jet-set lifestyle have a particular responsibility to try to reduce the pollution that they’re responsible for,” says the Sierra Club of California’s Bill Magavern.

I talked to Magavern this afternoon. He rides a bicycle, by the way… even on a rainy day like today.

[UPDATE, Wednesday 4:55pm: The folks from them PFT want to make it clear that the governor’s money won’t go toward planting trees… but rather, to protection of existing trees that might otherwise be logged. Spokesman Randall Beren said in an e-mail that many of the details of the governor’s payments for carbon offsets are still being worked out… including exactly how much money all of those carbon emissions are going to cost.]