Signs of Arctic climate change
But what I didn't know, is that this is something that apparently started in 2007, having all kinds of consequences for Northern Hemisphere weather patterns. This is again from the Dosbat blog, where Chris Reynolds is on a roll:
Last year I posted "Summer Daze." In that post I detailed a new pattern of atmospheric behaviour centred on high pressure over Greenland, this pattern is new since 2007, and as I showed is a robust change since the 1950s in NCEP/NCAR data.
Well, it's happened again this year...The pattern I showed consisted of strongly anomalous high pressure over Greenland surrounded by a ring of tendency to low-pressure anomalies. I used NCEP/NCAR monthly analysis to examine it (source data). As with all atmospheric patterns, in some years it was stronger than others, and there was interannual variability in the details of the pattern, but taking a succession of years it was seen to be a common pattern. The robustness of this pattern and its unusual nature is highlighted by taking the average pressure fields for batches of years and subtracting one batch from another. The pattern of the post 2007 period survives this method, still being present for any 5-year period subtracted from the period 2007 to 2011. As could be seen from the original Summer Daze post, this process shows that the pattern doesn't occur regularly in the past in the way it has done since 2007.
This year the pattern is textbook perfect.