Gavin Schmidt and Richard Alley made some comments on extreme weather here.
Dick Lindzen (via email) on cold and heat extremes:
"Gavin and Alley both seem pretty ignorant. Extremes of both cold and heat depend on advection by baroclinic eddies. This should get weaker in a warmer climate (assuming polar amplification which is another dicey matter). Alley is assuming that one just adds the change in global mean temperature to any current extreme. Marc shouldn’t be so defensive. He’s not dealing with experts. On the other hand, perhaps it should be noted that the reduction in extremes is ‘consistent’ with global warming."