You know, just asking. I started contemplating this as we were walking away from the Stadium and saw easily 100 semi trucks in the parking lot, with their diesel engines running of course. And then there was all the travel involved in getting 40,000+ people to the stadium from all over the state, plus probably lots of air travel (I doubt Bono sailed from Dublin or walked across the plains like the pioneers to get to Utah), plus all the pollution used in constructing the special stage and equipment, plus a whole lot of electricity to power the event, etc., etc., etc.
We were of course lectured on how wonderful the earth is and how democracy rocks and how we are all, like, totally ONE (who knew?).
Great concert, BTW.