With spring ascending to the throne at 4:44 a.m. this morning, still-shivering Northwesterners could be forgiven for wanting to celebrate the event like a second Mardi Gras. But could this chillier-than-usual winter be the first of a trend?
First, let's take a peek back at the winter that just went into hibernation.
UW research meteorologist Mark Albright says that since 1958, this past winter (which he defined as between Dec. 1 and Feb. 28 for this purpose) was the fourth coldest. The average temperature, which factors in highs and lows, was 39.1 degrees.
Colder winters were 1968-69 (37.3), 1984-85 (37.6) and 1971-72 (38.6). But if Mark were to expand the criteria to March 20th and count in the last weeks of winter, we might climb higher, as this March's average temperature is 40.8 degrees through the 18th -- nearly 5 degrees below normal. That's nearly twice as cold as last March, which was also pretty frigid, about 2.7 degrees below normal.
Now, this chart leaves out some of the historically cold winters of the late 1940s and 1950s, but there's a reason. While Sea-Tac Airport opened in 1945, they have moved the weather observation station a bit around the airport. It moved once in 1948, I believe, and then another move in 1956.
(I'm not exactly sure why, but I'm guessing it was that as the airport expanded, maybe the weather instruments were in the way? I can just picture having a big anemometer sitting in the middle of runway 16L or something. Not sure the pilots would appreciate having to dodge that, plus every three minutes, the airport would register wind gusts over 100 mph as a plane passed :) )
Anyway, Albright says the move in 1956 caused overnight temperatures to remain on average about four degrees warmer on clear nights. Again, this is my own theory but I'll bet the previous spot might have been in a bit of a valley -- the airport property does have a decent slope to it. Colder air pools in valleys since it is heavier than warm air, so you can get micro-microclimates where it's a few degrees cooler even in a shallow valley, and even over a few yards' distance. It could be a completely other reason, but this makes sense to me.
In any event, the move has made record lows more difficult to break, and indeed, many of Seattle's record lows still stand from the 1945-1956 period (including 1950, which owns 18 of the 34 record lows between Jan. 1 and Feb. 3, but I bet those records would still be there had the thermometer been in the current location.)
Could This Be A Sign Of Cooler Winters In The Short Term?
Global climate forecasting is an incredibly complex topic, what with the controversy over Global Warming and the like.
Remember that global warming is a long-term issue, not something that works over a year or 5 years or 10 years.
That said, there are some signs that at least the Northwest might go through a cooling phase here over the next few to several years.
(Caution, meteorological gobbledegook ahead next 20 paragraphs. Those already in Friday brain shutdown mode may want to save this reading for Monday or Tuesday.)
You might have heard of La Nina and El Nino -- which is a cycle where the Pacific Ocean waters in the equatorial tropics region bounce back and forth between being warmer than normal (El Nino) and cooler than normal (La Nina) over a 3-5 year period.
In El Nino years, the Northwest tends to be warmer and drier than normal, especially in winter. (These are a skier's worst enemy) while La Nina tends to be cooler and wetter. We've been in a La Nina for the past two winters, although it seems last spring and summer took the brunt of it. La Nina conditions are expected to weaken this spring and we should be neutral by summer, meaning a slow climb back to normal.
But, there is quasi-new research into a longer pattern, called the Pacific Decadal Oscillation (or PDO). This is a cycle where it's more the Pacific Ocean waters off the northern North American coast also undergo phases of warming and cooling, only these phases go on roughly a 30 year cycle.
Research indicates that we were in a warm phase from about 1920 to about 1947, when the phase shifted to the cold phase. The period from 1947 to about 1977 was marked by a series of cooler overall average temperatures, including the winter of the ages of 1949-1950.
Then, in 1977, it switched back to the warm phase, and the period from then through around 2000 was marked by much warmer temperatures.
After a few years of about neutral conditions, some researchers now indicate that 2007 might have been the shift back to the cool phase, which would time out about right with the 30 year cycle.
If so, it might mean the next 20-25 years could be generally cooler, although still sure to have years in there where it'll be warmer than normal. (See this chart here.)
La Nina and El Nino will still be occurring, but it might mitigate the El Nino a bit and enhance the La Nina, where as in the 80s and 90s, we might have been enhancing the El Nino years and mitigating the La Nina years.
And for snow fans, if you liked last December you can pin some hope on the fact that the winter of 49-50 was three years after the last shift to the cold phase. That would make the winter of 2009-10 three years after the shift, should 2007 have been "the shift" (Much like economic recessions and depressions, you really don't know for sure until you have several years' data to go back and declare when it happened.) Now, that's not to say Gig Harbor is going to freeze over again next winter, but just an interesting stat for those snow and cold fans out there to muse about :)
Does this thwart Global Warming?
No. Remember, global warming is a global event over several years, not based on what's occurring where you live this particular year or next. Sure, there is plenty of ammunition on both sides of the debate, but as a whole, many people tend to dismiss global warming for the wrong reasons -- like, say, pointing to the statistics I gave at the start of this entry and thinking "Oh, it's been cold this winter in Seattle. That proves global warming is false."
Last year in my blog, I tried to tie Global Warming to Ichiro's batting average, but I think I've got a better analogy:
Think of traffic in the Seattle area. There are days when traffic is light, and days when it is heavier. But as more people move into the region, traffic as an average is getting slightly heavier as time goes forward as there are more cars in the region to be on the road at any given rush hour.
So even though there might be a day when the freeway is mainly wide open and you can get from Seattle to Bellevue in 15 minutes, that doesn't mean our traffic problems are solved. Just as if that trip took an hour, doesn't mean you need to now sleep in your office.
It could be an extenuating circumstance -- it's a sunny day and people left early and traffic's lighter than normal, or there's an accident and it's raining and traffic is bottled up. As time goes on, unless something is done, that trip will take increasingly longer on average, but your daily commute has many other factors in play, just like the daily weather patterns have factors in play that can make an extended cold snap or heat wave.
So my contribution to the subject: Believe or don't believe in global warming for the right reasons :)