MIT professor Richard Lindzen is the most famous of the global warming denialists, and considered the model for the protagonist in the well known science fiction novel, State of Fear. He said in 2004 that temperatures are as likely to decrease as they are to increase - in other words, the middle point prediction for him is no change in average temperatures. By contrast, the likely temperature range announced by the United Nations Integovernmental Panel on Climate Change is an increase of .2 to .4 degrees Celsius over 20 years. I choose the middle of that range, .3 Celsius, for purposes of facilitating a bet. Halfway between the midpoint I chose on the IPCC range and the midpoint for a denialist (no change) is .15 degrees Celsius. Anyone who thinks Lindzen and the denialists are right should be attracted to this bet.
I believe there is a plethora of information for why my prediction is likely to be correct, starting here:
Brian A Schmidt is negotiating the terms of a bet about this prediction. It will soon be added to Bets on the Record.