One of the things about Global warming and the greenhouse effect is that there are a number of theories currently being examined. I think the easiest answer is that the complex nature of the problems mean that predicting events and trends are not easy either. We just don't know... which means that TDAT can cherrypick the best bits to make a dramatic film (though parts are, I understand based on current thinking... not much, but bits!).
For example, there could be warming combined with the return of the Ice Age - as we are in the middle of an interstacial period now (between Ice Ages). It has been argued that the Earth will balance out such changes and that these changes are indeed part of the natural order of these things - we've just not been around long enough to remember the last one!
Perhaps one of the key events will be the changes to the sea levels (which may rise, may not rise, may rise very suddenly or rise, then slow down!) and the consequential effects on global climates and ocean currents. One of the current thoughts (LOL) here in the UK is that although we could end up with a more Mediterranean-type climate, a change in ocean currents along the west coast of Britain, caused by a change in ocean currents may mean that the warming effect of the Gulf Stream Drift is lost, which will lead to a cooling down of the west coast landmass and the return of Ice... just too many variables.
You know, SubZ, I'd disagree with that - shouldn't you have a say in how you want the Earth to be in the future?It really makes me depressed to think about the future of the world, but I say it is not my judgement to determine its fate or future.
Might be worth reading Kim Stanley Robinson's Forty Signs of Rain.