Preservation and Press Coverage

I found this brief question and answer in the Chicago Tribune Parade, for August 3, 2003, page 2.
“Q. I read that Eddie Vedder and his group, Pearl Jam, bought 1400 square miles of endangered rain forest in Madagascar to compensate for the 5700 tons of greenhouse gas that will be created by the band’s U.S. tour. Who will it help?–Chuck S., Mesa, Ariz.
A. They didn’t buy the land but did give an undisclosed figure to Conservation International to protect that rain forest. It will help the 16.5 million people on the Indian Ocean isle of Madagascar and the five members of Pearl Jam, who hope to lure thousands of environmentally sensitive fans to concerts by convincing them that the band is politically correct. Sounds like a lot of gas to us.”
I’d like to know who came up with the figure of 5700 tons of greenhouse gas, and how they determined that figure?! I assume they figured in the vehicles used to move the tour from site to site, and maybe even figured the cost due to the electricity they are going to consume for sound, lighting and air conditioning. But did they add in the effects from beer drinking concert attendees? I wonder what else they might have missed.
And, since when is a band concerned with being politically correct? It’s lovely that they are helping to save the rain forest, but it’s an odd way to generate press coverage for a tour.