1) I believe it could be a problem, but when Caeser invaded the UK, southern England was described as 'A Land of Vines', which would have required the temperature to be somewhat higher back then, so temperature variances do happen. I think it's a serious concern, but too many people are looking for a 'Doomsday' these days.
2) Yes, they are fully aware of the risk. They are also fully aware of the cost of dealing with that risk. Global warming may not be a problem by itself, but may act as a catalyst to other, worse problems.
3) No. Tony Blair recently gave a speech (yesterday) stating that he feels the World needs to start acting more responsibly towards it's environment. For someone as Industry steered as Blair to make such a comment means quite a lot in World perspective, however, on should not forget the Elections in November.
4) I'll leave this to people with First Hand knowledge to answer, but my opinion from outside is that while it certainly has issues, Australia seems to be at least trying to consider their environment and to learn, where possible, from it's mistakes.
5) Any step taken is for the good at the end of the day, regardless of whether the danger is sooner or later, the less crap we pump into what we breath, the better. Cars are the biggest problem, but that is because of numbers, factories still pump out a hell of a lot.