Tim's Blog

I'd take you up on that offer if only I had the time to spare.

I think you're right they're different kinds of pollutants so difficult to make a proper comparison - the original article I'd read was in BBC Focus magazine months ago - the best I could find online was this:

http://philbattos.blogspot.com/2007/04/green-travel-ship-or-plane.html

which is not conclusive either.

I tried to have a look at the site you gave to get an idea of costs (just out of interest) but my broadband has decided to operate at sub dialup speed tonight!#!