While working on an El Nino story to be published soon, I happen to talk Monday morning to Ed Olenic, who forecasts seasonal climate for NOAA's Climate Prediction Center.
I know nothing about the Arctic Oscillation, but Mr. Olenic walked me through the basics of the extraordinary extent of the phenomenon, which I may as well do for those of you curious about the incredible cold gripping much of the nation.
I confess we in Southern California — the fortunate or the doomed, depending on your outlook — are enjoying a balmy New Year's week here in the opening days of 2010.
But that's not true in most of the nation. It's been extraordinarily cold.
Tthat doesn't mean global warming is over, unfortunately.
To make that point, and to introduce a major paper to come, Gerald Meehl of the National Center for Atmospheric Research explained this unfortunate reality with an eloquent graph he published today:
(Meehl is one of four climate scientists who testified on climate change to Congress, after the Democratic wins in 2008, by the way.)
In his words, the data this graph represents:
If temperatures were not warming, the number of record daily highs and
lows being set each year would be approximately even. Instead, for the
period from January 1, 2000, to September 30, 2009, the continental United
States set 291,237 record highs and 142,420 record lows, as the country
experienced unusually mild winter weather and intense summer heat waves.A record daily high means that temperatures were warmer on a given day
than on that same date throughout a weather station's history.
The authors used a quality control process to ensure the reliability of
data from thousands of weather stations across the country, while looking
at data over the past six decades to capture longer-term trends.
What does this have to do with the Arctic Oscillation?
We don't know. So I am told.
So let's turn back to how the Arctic Oscillation works.
What we know, said Olenic, is that the AO is about as low — negative — as it's ever been.
He then directed me to this graph on the Climate Prediction Center's vastly deep website:
Which gives us a notion as to how deep this dip into negativity is.
[Note: the black line is the instrumental record; the red lines represent a suite of models' speculation on how the AO will wax or wane in the next couple of weeks.]
Then he took me to another graph, showing what the Arctic Oscillation looks like in temperatures on a map of the world, seen from above:
Or, in the words of the caption:
Since the AO
has the largest variability during the cold season, the loading pattern
primarily captures characteristics of the cold season AO pattern.
Huh? I asked him, does the blue represent a negative condition that drives cold into most of the U.S.?
He said yes.
Here's a graph of the positive (left) and negative (right) phases of the Arctic Oscillation that I found helpful, from the National Snow and Ice Data Center:
The figure on the right represents the Arctic Oscillation in its negative phase, which is where we are now, bigtime. You can see above what this means for the cold and storm tracks, and explains why much of the U.S. and the U.K. is absolutely freezing.
(Or so I see on Flickr…here from Birmingham in the UK, in a picture taken today)
UPDATE: Weather writer John Cox adds a helpful description of how the AO works in its positive phase and negative phases:
When the pattern is positive, the winds are strong, and the power of
the vortex holds the storms in its embrace. When the pattern is
negative, the winds are weak, winter storms slide farther south and
their sub-freezing temperatures grip much deeper into the Northern
Hemisphere. As Andrew Revkin at the New York Times has pointed out recently, the Arctic Oscillation is more deeply negative this year than it has been since the 1980s.In
2001, after analyzing its impact on Northern Hemisphere winters,
University of Washington researchers suggested that effects of the
Arctic Oscillation on weather patterns "appear to be as far-reaching as
those triggered by El Niño in the South Pacific."
Kit Stolz 
It’s good to have an Idea of what will going to happen.. Great info.. Thanks..
LikeLike
The methodology of that eloquent graphic was debunked two months ago:
http://wattsupwiththat.com/2009/11/16/hall-of-record-ratios/#more-12867
LikeLike
Actually, Rob, that’s not true. In the opening to the Watts statistical essay, it’s stated:
“While this study does use sound methodology regarding the data it has included, it falls short of being both statistically and scientifically complete.”
It’s going to take me a while to read and think through this highly detailed objection to Meehl’s study — back later.
LikeLike
Rob:
I worked my way through Bruce Hall’s objections to the analysis by Meehl and NCAR. It’s highly detailed but not very convincing, in my view.
First of all, Hall argues that:
“The selection of 1950 through 2006 significantly biases the outcome of this study because the U.S. was entering a cooling period in the 1960s and 1970s which creates the illusion of unusual subsequent warming from 1980 through 2006.”
Well, it’s true that the climate variations play out over long periods of time, but a climatology is thirty years (that is, thirty years of weather). And the cooling period identified by Hall occurred at around the midpoint of the 56-year period studied by Meehl et al. So this objection is dubious. Warming found over the course of two climatologies is not likely to be a fluke, especially when combined with independently convergent verifying data from glaciers, ice sheets, phenology, etc. Birds and flowers are not going to be confused by numerical data from any source.
Hall claims the warming of the last twenty-five years is simply an oscillation and that “it is more probable that we may be facing a cyclical decline in our overall temperature and that something similar to the 1960s and 1970s may be a far more realistic projection.”
I attended dozens of presentations about climate at the AGU this year and heard not a single temperature projection along those lines. Not one, and plenty of others that projected a warming future. I’d be very interested to see a peer-reviewed paper that predicts a climatological (as opposed to seasonal) downturn in temperatures. Do you have one in mind, Rob?
To put it another way: Hall argues that the l930’s was a warmer period than recent years, to wit: “Now let us take the two data sets and plot the ratios and see what conclusions we might draw remembering that in absolute terms, the 1930 had a much higher frequency of maximum temperature extremes than the 1990s or 2000s or the combination of the last two decades.”
But the data he cites doesn’t make that point for this decade. According to the numbers he cites, in the l930’s we saw 2.05x as many a maximum-to-minimum (heat-to-cold) records set. In this decade, we’ve seen nearly 2.7x as many hot to cold records set. So it’s not a very good argument.
Hall’s second point is the familiar objection from deniers, that the urbanization of the nation and the attendant urban heat index has converted rural temps to urban temps, and thus distorted the record. I’m not going to debate that point today — I just don’t have time to go that far into the weeds right now. I’ll just say that it’s not very convincing, in part because plenty of scientists believe in both the urban heat index and global warming. The concepts are not mutually exclusive — far from it.
LikeLike