Anyone who lives in the north-central United States, or most areas of Canada, can agree with me here: Spring and summer have been incredibly cold this year.
Yesterday, I asked a climatology prof that I know, “Is there a reason for this? Or is it just a fluke?”
There was a reason, as he explained. And it’s incredibly cool (to me at least) and in no way proves that global warming is all wrong.
Let’s help the story along with a map, courtesy of World Atlas (doodles and arrows are my own).
The jet stream (the black curvy line on the map) is the boundary between the cold polar winds and the warmer temperate winds. In the Northern Hemisphere, when the jet stream is south of you, your area will be cold. When it is north of you, it’ll be nice and warm.
The northwestern Pacific has been warm this spring and summer. This warmth is pushing the jet stream further north. BC is experiencing the effects of this change – it’s had unseasonably hot, dry conditions, which are aggravating their already-worrisome forest fire problem.
When the jet stream peaks northward, the prof explained, it has to follow that with a trough. The peak on the West coast was very strong, so the trough further eastward, in the continental US and Canada, has also been very strong. Areas as far south as Chicago have had many days where the jet stream is south of them, so they’re submerged in polar air.
So all spring and summer, the jet stream has been “stuck” in the (very approximate) shape you see above. As an El Niño just began, our area would usually expect a warm winter. However, should the jet stream stay stuck in this shape…..we might have a colder winter than normal. The Prairie winters are bad enough already. I can only imagine the “so much for global warming” comments which would happen if such a winter came to pass.
So, in a strange way, our area has been so cold because somewhere else has been really warm. This can’t prove that the Earth is warming, as no single event can.
But it certainly doesn’t disprove it.
ClimateSight 
With an El Nino starting up we may be having a warmer and possibly green Christmas (central-northern Ontario, Canada) this year according to forecasts. If so, that will only be the second green Christmas we’ve had in at least 50 years, possibly quite a bit more.
A couple of questions:
1) When you say northeast Atlantic, do you mean northeast Pacific as shown in your picture?
2) Is there a good primer anywhere for what governs the shape of the jet stream and the convection cells? How does it get stuck in one configuration or another?
1) Jeez….yes….you’re right. I really need to get more sleep.
2) I’m still new on this issue as well – I’ll ask around and let you know if I find anything.
I’m glad to see that you’re posting more lately. This blog is becoming pretty popular.
In correcting the ocean, I think you also changed northeast to northwest… Is that right? If not, get some sleep before making additional corrections. ;-)
Is it east or west? Technically it’s in the Western Hemisphere, but then if you flew east over Japan and continued over the Pacific and kept going east you’d end up in the West……
http://en.wikipedia.org/wiki/Rossby_wave
How is that for a starter?
NOAA provides considerable monthly analysis of US climate as well as the BAMS State of the Climate 2008, being the latest years analysis. For this summer too links comment on the general pattern you note. The first has some climate anomalies and mentions the unusually persistent upper level circulation pattern. http://www.hprcc.unl.edu/articles/index.php?id=105
The second shows this pattern with high pressure over the west coast and low pressure over the southern Great Lakes creating a trough.
A ridge on our west coast is a blockage in the westerlies, forcing weather systems north around the ridge, eventually diving south bringing the cool weather with them. The reason for the persistence is not discussed. It typically is the result of several circulation systems reinforcing each other, being in synch so to speak.
The BAMS 2008 report is now out. http://www.ncdc.noaa.gov/oa/climate/research/state-of-climate/
Select 2008 report for a dissection of any aspect of the climate. This is a heavily peer reviewed report and meets your high standards. Having written one of the chapters, I can attest to that.
Cool – a glaciologist! We get lots of interesting commenters over here. Thanks for the links, I was wanting some explanations of this unusual weather pattern which were higher up on the credibility scale.