From my perspective, I can read my book equally well whilst sitting on an aircraft or on a train. I can't work while doing either (other people may differ, but my work isn't amenable to being done whilst travelling) so cost is king. For work travel, time is money so air will always win. For personal travel, I much prefer rail because it's more comfortable and I get more time undisturbed to read!One key difference these days is that the time on a train can be more useful, either for work or for whatever you'd do (within reason ) on the sofa.
Indeed, try transporting a few hundred thousand tons of iron ore from Brazil to Rotterdam by air and see how that works out environmentally. Shipping is one of the most fuel-efficient ways to transport cargo over long distances (I'd like to see a comparison between shipping and rail, I doubt if anything else even comes close) and to a first approximation, carbon dioxide emissions are proportionate to energy consumption.Shipping is certainly a terrible polluter but it's much, much better than air per kg over the same distance. While your average gargantuan container ship will be chuffing out CO2 all over the place, it's carrying such a mind-bogglingly huge amount of stuff that the unit cost is small.
One of the glaring issues, at least within the EU, is that VAT is payable on international rail journeys but not on international air travel.One thing I don't understand is the compatatively low cost of carbon offset. I worked it out for a Malaga to London flight recently, on a few sites. £7! Surely that can't be right?