That is interesting Fred. It would be great to see if there is a global trend in the frequency and severity of floods and droughts globally. With regard to the snow cover, there is no significant trend in Fall and Winter of the NH, but you couldn't have missed the obvious definable AGW trend in the NH Spring. I am sure you have also come across this handy page that shows 11 clear indicators of global warming. Unfortunately, it does not include the changes in biological systems that have already occurred. But i guess this somewhat off the topic of severe weather.
@Mueo - Given that the US has the best climate monitoring network, despite its issues, for a country of it's size (fifth largest), it is very likely that any trend (or lack thereof) seen in the US figures will be comparable elsewhere. With regards to the Spring Extent, I agree that there is a negative trend. However, attributation is debatable. I could probably find a graph for the PDO index and find some co-relation. Or if I could find a graph of the yearly output of black carbon (soot) from Chinese industry, I would likely find a STRONG co-relation.
@fnieuwenhuis - Thought you might like to check out this report, since it's on the same topic. Chapter 2 p. 47 has an interesting graph showing areas with an increase of intense precipitation events. The report also states that certain areas in NA have increased tendencies for drought, although the worst heat waves occurred in the 1930s and there is no trend for the whole continent. Out here in BC we have become aware of our warmer winters, allowing the mountain pine beetle to reproduce unhindered, and the drier summers contributing to forest fires (probably earlier snow melt is the problem there).
About the PDO, perhaps you could help me out understanding how an internal variation contributes to a global increase in temperature. Where does the energy come from? What other factors are in involved to explain the other changes, like the cooling of the stratosphere? How does it offer a more coherent explanation than the standard GHG attribution.
Black carbon is definitely a problem. I am with you on that one. Though, it is also definitely anthropogenic (mostly). But I guess your point is that CO2 is not a major problem. I must disagree on that. I recently listened to a talk on this issue. It is clear that black carbon a big problem. This provides yet another reason to get away from coal. However, black carbon doesn't stay in the atmosphere very long, unlike CO2.