Theoretically, those who believe the IPCC predictions should be able to make piles of money off those who are skeptical, because they wrongly predict minimal warming and we correctly predict... well, I can never remember what is is exactly: about 3 oC at CO2 doubling with error bounds. Now there are problems with making piles of money, because this is 50+ years in the future, and trying to predict with shorter horizons runs into problems with natural variability. But still, its an interesting idea. One of the other problems with trying to make bets is that the septics turn chicken on you... here for example we see James Annan trying to get Steve Schulin to face up to his words - an embarassing spectacle.
However, Mark Bahmer is made of sterner stuff perhaps - see comment 6 here.
I'll put this post up now as a marker for the idea.