The fossil fuel will probably last a bit longer than 50 years, working on the assumption that
some new reserves will be found. However, world use is increasing, and the rate of increase is also increasing...
Global warming? I think it's too early to tell. There may be some feedback involving quicker deposition of limestones removing CO
2 from the atmosphere, but AFAIK geologists, climatologists and meteorologists are retty evenly split on the issue; there's not really enough data yet. But if it
is irreversible, we don't really have time to wait and see
And there are arguments that the increasing sea-temperatures will mean that methane ice-hydrides (I think they're called) on the sea-bed will melt, releasing methane into the atmosphere. And methane is a greenhouse gas with (IIRC) of the order of 10 times the heat-trapping ability of CO
2 weight-for-weight.
And of course the emerging Asian economies, as you quite rightly say, will look at the USA's refusal to sign Kyoto, and say "if you won't cut CO
2 emissions, why the
should we?"
There's always the possibility that we could find a technology that will reverse global warming I suppose...
*Edited for spelling and added clarity... I hope