2006: warmest year on record in the U.S.

By: Dr. Jeff Masters , 9:18 PM GMT on January 09, 2007

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The United States recorded its warmest year ever in 2006, according to today's report issued by the National Climatic Data Center (NCDC). The 2006 annual average temperature was 55�F, 2.2�F (1.2�C) above the 20th Century mean and 0.07�F (0.04�C) warmer than the previous warmest year, 1998. The NCDC had estimated that 2006 would be the 3rd warmest year in U.S. history last month, but an unusually warm December pushed 2006 to the top. It was the warmest December on record in the Northeast U.S., and the 4th warmest December for the country as a whole. Only 1939, 1957, and 1933 had warmer Decembers. However, the statistics partially hide the extraordinary warmth that began on December 10 and continued until January 6, when New York City tied their all-time record January high temperature of 72�. During the month ending January 6, the Northeast was 14 �F above average, and the U.S. as a whole was 7� above average.

No cause for alarm?
"No cause for alarm. Enjoy it while you have it," said Mike Halpert, head of forecast operations at the National Oceanic & Atmospheric Administration's Climate Prediction Center, in a story run by CNN just before New York City's record warmth. The story continued, "The weather is prone to short-term fluctuations, and forecasters said the mild winter does not necessarily mean global warming is upon us. In fact, the Plains have been hit by back-to-back blizzards in the past two weeks." True, the weather across most of the U.S. has finally cooled off this week, and the rest of January should have near average temperatures. And I agree that one warm month of winter in one country in its warmest year in 112 years of record keeping is not evidence of global warming, particularly when there is a moderate El Nino episode going on. An El Nino can lead to significantly warmer winters in the U.S.--exceptional December warmth has also occurred in 1877, 1939, and 1957, all of which were moderate or strong El Nino years. I've plotted up a comparison of temperatures in December of 1957 vs 2006 (Figure 1), and one can see that the unusual warmth of December 2006 does have historical precedent. Taking a look at average U.S. December temperatures for all years in the historical record (Figure 2), we see that these temperatures do show quite a bit of noise, and there is no evidence of dramatic warming in the past 30 years.

Figure 1. Comparison of the departure of average temperature from normal for December 1957 (the the second warmest December on record in the U.S.) and December 2006. Image credit: NOAA.

Figure 2. Average December temperatures for the U.S. from 1895 to 2006. Image credit: National Climatic Data Center.

Rolling thirteens with the weather dice
Take a look at the trend December temperatures in Figure 2. It shows that the average temperature has warmed a little more than 1� F in the past century. It may not seem like much, but that is enough to significantly load the dice in favor of warmer winters. Six of the ten warmest U.S. winters on record have occurred in the past 15 years. Month long spells where winter is seemingly absent--as also occurred in January 2006, the warmest January in U.S. history--have become more common. Keep in mind that the weather of January of 2006--which blew away the previous record for warmest January by a huge margin (2� F)--occurred during a La Nina year, not an El Nino. What concerns me most is that the warming trend is not isolated to the U.S. The 1� F rise in temperatures the past century has occurred world-wide, thanks to global warming, and the temperature increase has been much higher in the Arctic--something the climate models have predicted would occur as a telltale sign of the human-caused addition of greenhouse gases to the atmosphere. In the past, an exceptionally warm winter month in the U.S., like December 1957 (Figure 3), was offset by much cooler weather elsewhere, such as we see in Alaska, Greenland, and northern Siberia. However, December 2006 had no such offsetting cool temperatures--it was more than 1� C above average over almost all the land areas of the Northern Hemisphere north of 40� north latitude (Figure 4). Colorado, whose three blizzards have been widely cited as evidence that winter has been severe elsewhere, still recorded temperatures about 1� C above normal in December 2006.

Figure 3. Global departure of temperature from average for December 1957, the second warmest December on record in the U.S. Note that the exceptionally warm temperatures over the U.S. are offset by much cooler weather elsewhere, such as in Alaska, Greenland, and northern Siberia.

Figure 4. Global departure of temperature from average for December 2006. Note that the almost the entire globe north of 40� north latitude was more than 1� C above average, with large areas more than 6� C (11� F) above average.

All this unusual heat in the northern high latitudes is going to significantly slow down the formation of ice over the Arctic Ocean this winter. Furthermore, the lack of the usual snows across the Arctic may allow the snowpack to melt much earlier than normal in spring, resulting in more record warmth in the Arctic this summer. Arctic sea ice coverage, already down 20% in the past 20 years, is likely to continue to shrink in 2007. As sea ice melts in response to rising temperatures, it creates a positive feedback loop: melting ice means more of the dark ocean is exposed, allowing it to absorb more of the sun's energy, further increasing air temperatures, ocean temperatures, and ice melt. The observed changes in the ice cover (Figure 5) indicate that this feedback is now starting to take hold, and the weather dice will continue to get more loaded towards rolling higher numbers in 2007. I do think we're due for a cold winter next year--part of the warmth of the past two winters is probably due to the normal random fluctuations in the weather, and Nature has been rolling twelves more often than snake eyes of late. However, we're not going to see snake eyes too much more. December's weather in the Northeast U.S. may have been a case of the weather dice coming up thirteen--weather not seen on the planet since before the Ice Age began, 118,000 years ago. The weather dice will start rolling an increasing number of thirteens in coming years, and an ice-free Arctic Ocean in summertime by 2040 is a very real possibility, as indicated by computer modelling studies published in the Journal of Geophysical Research last month. This possibility is cause for alarm, and I, for one, had a lot of trouble enjoying the phenomenally warm weather of the past month here in Michigan.

Figure 5. Percent change in coverage of Arctic sea ice in Decembers from 1979-2006, compared to the 1979-2000 average. The Polar Ice Cap has shrunk by about 15% in December, and 20% in summer, over the past 20 years. Image credit: National Snow and Ice Data Center.

Check out the realclimate.org post on this winter's anomalous warmth.

I'll be back Thursday afternoon or Friday with a look at the status of El Nino. Will it still be around during hurricane season?

Jeff Masters

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599. weatherboykris
6:47 PM GMT on January 11, 2007
I don't know.But still, it could happen.
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598. Thunderstorm2
6:46 PM GMT on January 11, 2007
whats the chance of that happening?
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597. weatherboykris
6:43 PM GMT on January 11, 2007
who knows?Maybe some top level NOAA scientist will read this blog,get interested in the idea, and 20 years from now we'll all be saying what a genius he is.(CB,not the NOAA scientist)
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596. weatherboykris
6:43 PM GMT on January 11, 2007
who knows?Maybe some top level NOAA scientist will read this blog,get interested in the idea, and 20 years from now we'll all be saying what a genius he is.(CB,not the NOAA scientist)
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595. Thunderstorm2
6:39 PM GMT on January 11, 2007
mentally and physically hurt? It gets really annoying when he keeps going on about tunnels, we've all heard it before
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594. weatherboykris
6:38 PM GMT on January 11, 2007
even if the idea is flawed, it's a nice sentiment.
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593. weatherboykris
6:37 PM GMT on January 11, 2007
They're his or her own.He says he was mentally and physically hurt by andrew and wants to make sure it never happens to anyone else.
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592. Thunderstorm2
6:36 PM GMT on January 11, 2007
i was wondering were CB getts his idea for tunnels
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591. weatherboykris
6:33 PM GMT on January 11, 2007
It has great descriptions of all the computer models, modification theories,recon history,and a great section on forecasting Andrew
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590. weatherboykris
6:32 PM GMT on January 11, 2007
the book hurricane watch is great,orion
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589. orionRider
18:30 GMT le 11 janvier 2007
I Read something more interesting than tunnels to kill hurricanes. Some kind of a hydrophilic powder that can suck enormous amounts of water and precipitate as a solid to the sea, where it dissolves harmlessly. Only a 'reasonable' amount of the stuff would suffice to tame a large storm, I think it was a few thousand tons (!) dropped by a couple hundred planes over the eyewall.
Dresden got much more from 2000 bombers back in 1944, so it is at least feasible, if only the magical stuff can be cheaply produced in large quantities...

Do you know of this and is there a link with more info, or was it a hoax?
Where can I find information about genuine studies to kill or deviate hurricanes?
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588. Thunderstorm2
6:28 PM GMT on January 11, 2007
That comet looks cool
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587. weatherboykris
6:12 PM GMT on January 11, 2007
Catastrophe, to learn about TCs, start here.Some of the abreviations, such as WADL aren't used very often at Wunderground though.Link
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586. orionRider
18:11 GMT le 11 janvier 2007
Thanks for the answer, Patrap.
Love the photo between the trees (17:52)! Really gorgeous.
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585. weatherboykris
6:11 PM GMT on January 11, 2007
Something else I noticed about last year, a lot of African waves had trouble separating from the ITCZ
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584. weatherboykris
6:10 PM GMT on January 11, 2007
We'll have to wait and see if activity ever slows down in the next two decades.There's really no other way to see one way or another.
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583. weatherboykris
6:09 PM GMT on January 11, 2007
Regualr model overview...Link
Kind of old, but still useful.
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581. weatherboykris
6:04 PM GMT on January 11, 2007
Last year, even though we were in the warm AMO which should have caused above normal activity:
Ambient Sea level pressures were higher than normal.
an El Nino started.
There was a lot of Saharan dust.
Instability was below normal.
Relative Humidity was below normal
SSTs were near to only slightly above normal.
Non-El Nino wind shear was unusually high.
So, last year,even though practically all conditions were unfavorable for development, we still had a near normal season,which is a good example of just how influential the AMO is to seasonal activity.
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580. weatherboykris
6:00 PM GMT on January 11, 2007
well,if only it were that simple,catastrophe.For one, we are in the warm AMO cycle, which means that even in neutral conditions,all else being equal,we'd have an above average year.Also,there are other factors which include:
Saharan Dust
Non-El Nino induced Wind shear
SSTs in the Atlantic
The relative humidity of the atmosphere not related to Saharan dust
Ambient Sea Level pressures
And instability in the atmosphere.
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577. catastropheadjuster
5:35 PM GMT on January 11, 2007
Weatherboykris & MichealSTL Thank you. So if everything pans out right it ought to be a normal season. I know everyone would love to see one like last year. But you never know it might be cause they really missed it last year on the prediction. But it was nice to have a quite season. I know it's way to early to predict this year I was just trying to get around about ideal. But don't it depend on where the High is at in the Alantic Ocean to?
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573. mrpuertorico
1:46 PM AST on January 11, 2007
tunnels are not popular!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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568. weatherboykris
5:41 PM GMT on January 11, 2007
you took that,Patrap?
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565. weatherboykris
5:35 PM GMT on January 11, 2007
I've noticed that,STL.It is in the same spot as where the current positive anomalies originated from.I don't think we'll see a switch back to El Nino once we're nuetral.
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564. weatherboykris
5:30 PM GMT on January 11, 2007
catastrophe;When talking about El Nino,there are three descriptions meteorologists use.They are:
El Nino(Also called "warm conditions"):El Nino's are characterized by warmer than normal SSTs in the central Pacific near the equator.They typically decrease Atlantic hurricane activity.
Neutral:This means that SSTs are near normal in the Central Pacific near the Equator.Neutral conditions don't enhance Atlantic hurricane activity,but they don't inhibit it either.
La Nina(also called "Cold Conditions):La Ninas have colder than normal SSTs in the Central Pacific near the Equator and typically enhance Atlantic Hurricane Activity.
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561. catastropheadjuster
5:18 PM GMT on January 11, 2007
Thank you Skyepony & Weatherboykris, Skyepony are they more less saying it will probaly be a season like last year. With them saying el nino will be back during the worst of hurricane season? Or am I not understanding. When you'll are talking about neutral does that mean it's gonna be a calm season? I don't mean to ask to many questions I'm just trying to learn so I can understand more.So when hurricane season does come I can understand what everyone is saying. Thanks for taking time to explain this to me. I'm learning.
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560. orionRider
17:22 GMT le 11 janvier 2007
You were afraid I would really talk about tunnels, eh?
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559. weatherboykris
5:22 PM GMT on January 11, 2007
thanks Patrap
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558. orionRider
17:22 GMT le 11 janvier 2007
Why is it that on my picture the tail is long and narrow while it is rather triangular on other picts I've seen?

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555. orionRider
17:03 GMT le 11 janvier 2007
Blast the weather. Stood half an hour in the storm waiting for the clouds to part... No joy, no comet :-(

No answer to my 'comet' question either. I'd better talk about tunnels. At least they're popular...
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553. weatherboykris
5:11 PM GMT on January 11, 2007
Hi thunder2
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552. weatherboykris
4:56 PM GMT on January 11, 2007
How's this for a persistant weather pattern?
Who knew there was a NWS office in Guam anyway?
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551. Thunderstorm2
4:55 PM GMT on January 11, 2007
hello everyone
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550. hurricane23
11:50 AM EST on January 11, 2007
Yes a Kelvin wave might spark up warm anomalies in the coming weeks but overall neutral conditions are quite possible during the heart of the season.Lets see how things pan out in the coming months as we still got a ways to go before having to worry about tropical systems across the atlantic basin.
Member Since: May 14, 2006 Posts: 8 Comments: 13846
549. weatherboykris
4:23 PM GMT on January 11, 2007
Yes,Skye they have been inconsistent.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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