Apparently the Oceans absorb alot of CO2 through there plankton that floats around in it.. not an excuse to cut down a whole Brazillian rainforest, but a thought..
AVGAS I see on it's way out. With Diamond's and Thialert's (sp?)
new disel/AVTUR hybrid twin turbocharged out of a A-Class Merc engine as being the start, SMC from France also make a 300 HP turbo diesel piston as well with a view of replacing those connies in C182s and C206 etc. They're all water cooled too so hopefully less chance of thermal shock.
As for the AVTUR supply, as a earlier poster said, Aussie has a few reserves of gas condensate. I'm not entirely sure where, probably because I'm a kiwi and I haven't brushed up on my Aussie geography. Failing that, diesel fuel can be grown. Linseed and rape seed plants produce a large amount of oil which can be turned into biofuel. The Moller skycar for example has rotary engines that can run on used fish and chip frying oil.
Green house gases I hear you call, well with biodiesel, that doesn't really contribute to the problem. Why? Well when you grow these plants, they take the CO2 out of the present atmosphere, and act as carbon "sinks". The problem with fossil fuels is that there are in the ground, the carbon there is not already in the atmosphere, where with growing plants, it just takes the carbon already present in the atmosphere.
But in the big big picture of things, I can see us switching to a hydrogen fuel based society, once we iron out supply and containment problems. Hydrogen only acts as a fuel transfer medium, you can't mine it, you have to produce it using a power source. The other problem is the density of the stuff. You have to keep it really cold and under high pressure to turn it into liquid. So hydrogen fuel turbine aircraft might be a while away yet, as the tanks would have to be pretty huge.
There is also the chance that we may goto Methane, which can be mined off the ocean floor in deposits or produced biologically.
Turbines are hardy things, they can burn just about any fuel. I've even heard of turbines being fueled by coal dust for power generation on the ground. (The first officer's duties now include stoking the boiler and shovling coal..
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By this time, air travel might not be as what you know it presently. Long haul travel might take the route of ex-atmospheric travel, i.e orbital etc.
Oil is on it's way out, however it will be a gradual process. It won't happen overnight, but it will happen.