Megan McArdle offers an appropriately cynical explanation for why air travel tends to be neglected in conversations about how we might reduce carbon emissions:
Giving up air travel and overnight delivery is much more personally costly for the public intellectuals who write about this stuff than giving up a big SUV. If you live in one of the five or six major cities that contain virtually everyone who writes about climate change, having a small car (or no car), is a pretty easy adjustment to imagine. On the other hand, try to imagine giving up far-flung vacations, conferences, etc. — especially since travel to interesting locales is one of the hidden perks of not-very-well remunerated positions at universities, public policy groups, nongovernmental organizations, and yes, news organizations.
In fairness, there are many public intellectuals who’ve taken a strong stand against air travel, including George Monbiot, a staunch left-of-center environmentalist, and Saul Griffith, an environmental activist and technologist who strictly limits his air travel. But my sense is that Monbiot and Griffith are exceptions.