Science behind the January Heatwave

(From January 4, 2007 Christian Science Monitor)

The article says a climate pattern called the North Atlantic Oscillation (NAO) is probably the most immediate cause of the balmy weather:
The phenomenon swings between two states. When the NAO is positive, a large region of high pressure appears over the central Atlantic, while a large area of low pressure settles over southern Greenland. Each of these features are stronger than usual, leading to more-severe Atlantic storms that travel on a more northerly track than usual. This leads to wet, mild winters in the Eastern U.S. and northern Europe. When the NAO goes negative, the high and low pressure areas weaken and shift south. Storms are weaker and travel more directly west to east.

The NAO can have wide-ranging ecological effects—from changes to the location, frequency, and intensity of storms and wildfires to shifts in crop and fisheries yields. And it can have a profound effect on energy demand. Energy analysts note that crude oil and natural gas prices have eased, partly because of the mild winter so far.

The next question to ask is whether global warming is exacerbating the NAO—and that’s where scientists are less sure. Part of the problem is that unlike other well-known climate patterns (like El Niño), NAO is hard to predict and track. So NAO is something of a mystery—for now.

For the article...