First, everyone should read the letter by Lord Monckton concerning his follow-up testimony to Congress:
Second, everyone should read the post by Dr Roy Spencer concerning global warming Q&A:
Third, as a non-climatologist, I will present my views as an AeroSp. Engr. (PSU - BS '69, MS '71) and a person quite familiar with process control theory, systems and behavior. The computer models used by the AGW proponents and the IPCC assume that the Earth's climate system is unstable - small perturbations in CO2 levels will produce wide temperature swings due to positive reinforcement from other systems, thus driving Earth's temperature drastically higher.