If I have interpreted this correctly, this has some interesting ramifications. Increased north/south winds imply more mixing of tropical, temperate, and polar regions, and this got me thinking again about something I have wondered about for a while — to wit:

Since the radiative power is proportional to the fourth power of absolute temperature, for the same mean temperature, the less the variation of temperature (e.g. between the tropics and the polar regions), the less total power is radiated away. Put another way, for the same power radiated away, the mean temperature must be higher if the variation is lower.

A simple example illustrates the concept and gives an idea of the order of magnitude of the effect. Split the earth into two zones of equal area: tropical and non-tropical. The tropical area has a temperature of 300K (~27C), and the non-tropical area has a temperature of 280K (~7C). If the mixing were improved (as by increased north/south winds) so that the tropical temperature were reduced to 299K and the non-tropical temperature were increased to 281K, the net radiated power would be reduced by a fraction of a percent.

This would cause the total temperature to increase until the net radiative power again balanced the incoming solar power. In this very simple example, the mean temperature would have to increase a full 0.1K to radiate this same amount of power with a spread of 18K instead of 20K. (I was surprised when I crunched the numbers how big this value was.)

Given that by all accounts we are seeing this reduced differential between tropical and polar temperatures of about this magnitude, I wonder how much of the increase in “global mean temperature” could be ascribed to this effect.

It would seem that slowly but surely, after a minor hiatus in the late 70s and 80s, climatic winter has lengthened, especially at the tail end. Especially since the mid 90s. Summers don’t seem to have quite as many interior outbreaks and more onshore push. Falls are far more variable, with about one in four being OK and the rest early and unseasonably wet. Winters and even Springs seem to have more serious cold cP outbreaks. For example, after the low elevation snow event of 1976, there was absolutely nada through the rest of the 70s, through the 80s and into the mid 90s. We did have that really bad (dry) freeze late Dec ‘90 – early Jan ‘91. But that was about it. Then suddenly, after the ‘97-’98 El Nino, everything changed and it seems that the capability for there to be more frequent serious low elevation snow events, and other cold episodes, was unleashed. We had the sea level snow event on Dec 20, 1998, and then a bad freeze into the New Year. Low snow in Feb 2000. I think there was one in winter 2003 – 04 but may be mistaken on that one. Very early mountain snow in the high country Oct 2004 and a couple good low elevation snow events (to sea level) Feb – Mar 2005. Repeat of that Feb – Mar 2006. Then, although a dry winter overall, 2006 – 2007 obviously was disasterous in terms of cold, especially the record breaking Jan 2007 Great Freeze.

Bottom line, weather has gone downhill over the past 10 years. It is colder, more biased toward abnormally high rainfall, and generally more “northern.” I’ll stick my neck out and call it a climate shift, and not the type that Al Gore wants to talk about.