Tim,
which is the lesser of two evils, fossil carbon or new carbon?
I'd say it's pretty clear that our major priority must be to stop putting any 'new' carbon into the atmosphere, so yes, it's got to be better to re-use existing carbon rather than releasing 'new' carbon from fossil sources. I think the idea of using renewable-generated energy to crack water to make hydrogen fuel is a great idea, especially for long-range transport requirements.
But that's not nearly enough. It looks like we're going to miss the 2C target, and if it gets to 3.5C we're pretty much dead, so I would expect longer term we could hopefully develop planetary-scale carbon capture technology to start to reduce the overall load. But I believe the idea that if we can do a bit of carbon capture we can carry on running around is gas-guzzlers is simply not viable.
