There are calculators on line that will give estimates for emissions but the estimates vary wildly. I'll let you do your own research here, but I've used a couple of average numbers here for my personal use.
As a guess:
- Nonstop return flight from San Francisco to London = 3.3t
- Average car use for a year = 4.6t
As I need to fly twice this year, the flights are my biggest impact. In fact I really don't drive that much at all these days.
Just to muddy the waters further this is an interesting article about the time scales of various pollution sources.
So there aren't easy answers but generally it's not rocket surgery, we should all try to fly and drive less.
Teleconferencing and Working From Home
Virtual Reality, Augmented Reality and Tele-presence are all technologies that will allow us to interact with the world without the need to burn vast amounts of fossil fuels. In my last year at NVIDIA I learned to work from home several days a week. It was an adjustment in style but I was definitely productive and less stressed. I also presented at an entirely virtual global conference which was a good experience, the audience seemed engaged and asked good questions at the end which is a good indicator of success in my opinion, so it can work.