Arctic climate change: the past 100 years

By: Dr. Jeff Masters , 1:56 AM GMT on February 12, 2007

The Arctic is a region particularly sensitive to climate change, since temperatures are, on average, near the freezing point of water. Slight shifts in the average temperature can greatly change the amount of ice and snow cover in the region, due to feedback processes. For example, as sea ice melts in response to rising temperatures, more of the dark ocean is exposed, allowing it to absorb more of the sun's energy. This further increases air temperatures, ocean temperatures, and ice melt in a process know as the "ice-albedo feedback" (albedo means how much sunlight a surface reflects). The 20% loss in Arctic sea ice in summer since 1979 has given rise to concerns that this "ice-albedo feedback" has taken hold and will amplify until the Arctic Ocean is entirely ice-free later this century. Should we be concerned? Has the Arctic been this warm in the past and the sea ice survived? The answers are yes, and yes.

Figure 1. Annual average change in near surface air temperature from stations on land relative to the average for 1961-1990, for the region from 60 to 90┬░ north. Image credit: The Arctic Climate Impacts Assessment (ACIA).

The past 100 years
The Arctic Climate Impact Assessment (ACIA), published in November 2004, was a uniquely detailed study of Arctic climate compiled by 300 scientists over three years. The study found that while temperatures in the Arctic have increased significantly since 1980 (Figure 1), there was also a period in the 1930s and 1940s when temperatures were almost as warm. If one defines the Arctic as lying poleward of 62.5┬░ north latitude (Polyakov, 2003), the 1930s and 1940s show up being warmest period in the past 100 years. Looking at Figure 1, one cannot dismiss the possibility that temperatures in the Arctic oscillate in a 50-year period, and we are due for a cooling trend that will take temperatures below normal by 2030.

However, the period since 1980 was a time when the entire globe (except the bulk of Antarctica) warmed, and the 1930s and 1940s were not. Thus, the 1930s and 1940s warming in the Arctic is thought to be fundamentally different. Furthermore, the past 20 consecutive years have all been above normal in temperature, whereas during the 1930s and 1940s there were a few cooler than average years interspersed with the very warm years. A detailed breakdown by month and region of the 100-year history of Arctic temperatures was performed by Overland et al. (2004). They found no evidence of a 50-year cycle in Arctic temperatures, and concluded that the warming since 1980 was unique. However, they stopped short of blaming the recent warming on human-emitted greenhouse gases (anthropogenic forcing). The ACIA, though, concluded that humans were likely to blame for the recent Arctic warming, but not definitely:

It is suggested strongly that whereas the earlier warming was natural internal climate-system variability, the recent surface air temperature changes are a response to anthropogenic forcing. There is still need for further study before it can be firmly concluded that the increase in Arctic temperatures over the past century and/or past few decades is due to anthropogenic forcing."

This is the first in a series of five blogs on climate change in the Arctic that will appear every Monday and Thursday over the next two weeks. Next blog: The skeptics attack the ACIA report--and how the position of the pole star is indicative of Arctic climate change.

Also, be sure to visit our new Climate Change blog, written by Dr. Ricky Rood of the University of Michigan.

Jeff Masters


Overland, J.E, M.C. Spillane, D.B. Percival, M. Wang, H.O. Mofjeld (2004), "Seasonal and Regional Variation of Pan-Arctic Surface Air Temperature over the Instrumental Record", Journal of Climate, 17:17, pp3263-3282, September 2004.

Polyakov, V., et al. (2003), "Variability and Trends of Air Temperature and Pressure in the Maritime Arctic, 1875-2000", Journal of Climate, 16, 2067-2077.

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253. hurricane23
11:24 AM EST on February 14, 2007
It really wasn't that bad across miami cloudy skies with some light rain.The florida keys saw incredible rain amounts with areas seeing up to 9-10 inches of rainfall.Had some friends calling on my cell telling me there cars were flooded down there.Amazing amounts.

Member Since: May 14, 2006 Posts: 8 Comments: 13868
252. Patrap
10:21 AM CST on February 14, 2007
Heres a video I took exiting the trailer as we saw the TVS..was before the 2:28 warning.Wasnt going to play with that one..
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251. V26R
4:22 PM GMT on February 14, 2007
Those storms are Very Nasty
Was never near one, but seen what they can do
to communities, Glad you and your Family are Okay
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250. Patrap
10:19 AM CST on February 14, 2007
But daughter was 2 blocks from Uptown Carrolton Tornado..very lucky .
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249. Patrap
10:19 AM CST on February 14, 2007
7 miles se..about 12 due east..
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248. V26R
4:14 PM GMT on February 14, 2007
How'd you make out with that Nasty Weather Yesterday Adrian?
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247. V26R
4:13 PM GMT on February 14, 2007
Hey Dude,will do
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246. hurricane23
11:11 AM EST on February 14, 2007
Hey V26R!Check your mail.
Member Since: May 14, 2006 Posts: 8 Comments: 13868
245. V26R
4:08 PM GMT on February 14, 2007
Hey Trap, how close were the Twisters to you?
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244. V26R
4:03 PM GMT on February 14, 2007
If any you guys out on the West Coast With Boring Weather want to see an Ice Storm, check this out

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243. Patrap
10:03 AM CST on February 14, 2007
..from Todays Times Picayune in New Orleans

Wednesday, February 14, 2007
By Mark Schleifstein

National Weather Service forecasters issued an eerily accurate forecast 24 hours before a thunderstorm produced at least one tornado that ripped across the West Bank of Jefferson Parish and New Orleans early Tuesday.

On Monday at 3:24 a.m., forecasters in the Slidell office of the National Weather Service warned of tornadic supercell thunderstorms, accompanied by winds as high as 79 mph, golf ball-sized hail and the potential of a tornado ranked as a 3 on the new Enhanced Fujita Scale.

It estimates wind speed on a scale of 1 to 5, based on damage measured on the ground after the event. A 3 is equivalent to winds of 136 to 165 mph.

Robert Ricks, the lead forecaster who oversaw the meteorologists on duty during the early mornings both Monday and Tuesday, said that in approving the forecast, he relied on only one of several weather forecast models that predicted the tornadic storms would form. The other models, he said, indicated the storms would form later in the day on Tuesday.

Weather officials quickly doubled their forecasters on duty early Tuesday. And Monday at 3 p.m., they briefed emergency operations personnel in parishes throughout southeastern Louisiana about the upcoming storms.

Adding to the concern, Ricks said, was the memory of the Feb. 2 tornado that cut a wide swath through central Florida, killing 20 people. That twister had dropped from the sky in the middle of the night, catching many residents unaware, including a number who lived in trailers.

Ricks said his staff had carefully watched the forecasting measures taken by their cohorts in Florida, especially the problems caused by the early-morning arrival. That resulted in additional language added to forecasts during the day Monday, warning people living in FEMA trailers to watch the skies and find shelter in the event of a thunderstorm.

By the time Ricks returned to duty in Slidell at midnight Monday, the forecast was turning into reality.

Forecasters were watching so-called "rogue cell" thunderstorms form in advance of a squall line of connected thunderstorm activity that had formed well in advance of a strong cold front.

"We put up a (weather) balloon at midnight, and it came back with readings showing that the air mass had really destabilized quickly, compared to the 6 p.m. balloon," Ricks said. "The moisture content was much deeper, and the spin of winds at different levels was like going up a spiral staircase, increasing in speed as you go up in the atmosphere." "I remember making a comment to the radar operator that that's bad news for the city of New Orleans," Ricks said.

The office issued the first warning at 2:28 a.m.: A potential tornado was heading toward Boutte, Hahnville, Metairie and Kenner. That was 34 minutes in advance of the first damage in Westwego, Ricks said. The storm moved east, and warnings followed for Marrero, Harvey, Avondale, New Orleans and Chalmette

A 3:12 a.m. update added the Lower 9th Ward, Arabi and an area south of Lakefront Airport. Forecasters said that was a second tornado dropping from the same thunderstorm, which cut through Pontchartrain Park.

On Tuesday, a National Weather Service team surveyed the damage and concluded the supercell created two separate tornadoes. The first carved a path two miles long and 50 yards wide across the West Bank, beginning in Westwego, as an F2 on the Enhanced Fujita Scale, with winds estimated between 111 and 135 mph. It then jumped the Mississippi River and weakened to F1 strength, between 86 and 110 mph, cutting through Uptown and Carrollton.

Forecasters said a second tornado, also an F2, descended near the intersection of Franklin Avenue and Mendez Street, then cut across Pontchartrain Park to the Industrial Canal.

"It's very rare to see two F2 tornadoes touch down in New Orleans on the same day, only five or six miles away from each other," National Weather Service forecaster Phil Grigsby said.

Before Tuesday, only 14 tornadoes had touched down in New Orleans since 1950, according to the National Climatic Data Center.

State Climatologist Barry Keim said that April is the peak month for tornadoes in Louisiana, with a secondary peak in November. Between 1880 and 1989, there were 36 tornadoes ranked F1 or stronger in February in Louisiana, compared with 74 in April. Twisters are least common in summer, Keim said.

Daniel McCarthy, warning coordination meteorologist for the National Weather Service's National Storm Prediction Center in Norman, Okla., said the Tuesday tornadoes should reinforce the weather service's efforts to get people to buy National Oceanic and Atmospheric Administration weather radios. The radios can be programmed to turn on automatically when a tornado or other dangerous weather event occurs.

"I think it's imperative that you keep an eye on the weather when the Storm Prediction Center issues a warning," he said. "When a tornado watch is issued, you need to keep abreast of the situation, even at 3 in the morning."
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242. Patrap
9:59 AM CST on February 14, 2007
Thanks jake..have a good day too.Happy Valentines to you and yours too.
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240. V26R
3:43 PM GMT on February 14, 2007
I'll trade you guys out West any day for the Ice Storm and Cold Weather We're having right now in NYCity ANY DAY!!!
Be Careful for what you wish for!!!
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239. lightning10
7:34 AM PST on February 14, 2007
I would love to trade my near 90 degree day on Friday for a bit of rain here in So Cal. The weather is so borning right know compaired to other parts of the contery.
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238. Drakoen
3:23 PM GMT on February 14, 2007
guess no one is talking about the extreme cold coming tosouth florida with temperatures only in the 50s as daytime highs and low temperature near freezing
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237. jake436
3:06 PM GMT on February 14, 2007
Thanks, Patrap, and tell your daughter happy birthday, and your sweetheart happy Valentine's day!
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236. Patrap
6:57 AM CST on February 14, 2007
I got the pic from a AP photog friend.She sends me photos of events for here!..Glad your friends made out well...the pic was taken before SUnrise or around that time I believe.I was in Ponchatrain Park briefly..but my batteries failed on my cam...go figure.Heres the Headlines from this morning.Daughter was where the star is above the W in twister.Shes 16 today!..Patrap7
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230. jake436
3:56 AM GMT on February 14, 2007
PATRAP-Yes, that is the house to which I referred earlier. Did you take that picture? My wife found a video of it on while she was at work, but I didn't see it, and couldn't find it later. I was just checking in to see if you responded, and you've got the picture. You 'da man, brother! And by the way, was that pic from this morning b-4 daylight, or this evening, after sunset? My wife talked to her this evening, and she said the house appears to be leaning more and more, and she fears it will begin to further damage her house. As you can see in the pic, the leaning house is far bigger than our friends. She had the power meter ripped off the side of her house, so she's not staying there tonight anyway. She's getting windows replaced tomorrow, and the church next door helped her with the trees this morning. Will be her 3rd new fence in three years!
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229. tornadodude
3:45 AM GMT on February 14, 2007
Most Snow in 24 hours in Springfield Rank Amount Date
1 15.0 inches Feb. 28, 1900
2 13.3 inches Jan. 1-2, 1999
3 12.6 inches Jan. 30-31, 1914
4 11.1 inches Feb. 12-13, 2007
5 10.9 inches Dec. 19, 1973
6 10.7 inches Feb 12, 1894
7 10.5 inches Dec 24, 1915
8 10.3 inches Feb 23-24, 1965
9 9.4 inches Mar. 19-20, 1906
10 9.0 inches Feb. 15, 1903
NWS Central Illinois

Notice that 5 of these occur in February...

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228. tornadodude
3:42 AM GMT on February 14, 2007
is the snow in the northwest section begining to drop southeast?
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227. tornadodude
3:37 AM GMT on February 14, 2007
hi all.... about 2-3 inches of snow here... with about a tenth to a quater inch of ice underneath.... the low really deepened as it moved over southern Indiana...
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226. Skyepony (Mod)
2:19 AM GMT on February 14, 2007
gfs starts it warm core.
cmc slightly warm..I agree how this & the next ones takes it as the low that has been treking across instead of a new storm that forms in the Atlantic.
& the winner for most crazy warm storm, 2 nights in a row is, the, Ukmet...

Did you atleast see a drop of rain lightning?
Member Since: August 10, 2005 Posts: 397 Comments: 43366
225. Skyepony (Mod)
2:19 AM GMT on February 14, 2007

Member Since: August 10, 2005 Posts: 397 Comments: 43366
224. lightning10
2:16 AM GMT on February 14, 2007
The weather in So Cal was quite borning today compaired to most of the nation, however there was still something to talk about.

All day thunderstorms have been poping up about 10 miles to the east of my area. There was a few good thunderstorms today.
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223. Brandonr007
1:12 AM GMT on February 14, 2007
Up here in Halifax, Nova Scotia..Looks like the low is getting ready to form off the SE coast and head up this way..Saw a link last night that some of the models think this low will have a warm core..INTERESTING to say the least...I know there is a lot of press on this system right now but I got a bad feeling that this storm is really going to deepen fast and be stonger then most are predicting..Might be one for the record books..A ton of tropical air, storms in the south, Cold artic air in the north and water temps in the NE Atlantic are above normal..Dare I say THE PERFECT STORM????? Anyone agree or disagree..I say this turns into a Massive BOMB and pressure gets down to the 960MB range!!!
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222. stormy3
12:10 AM GMT on February 14, 2007
Hi all! just got home from PA last night. talk about good timing or is it? Now i'm watching weather alerts all over Florida. My daughter lives just outside of State Collage and she says it's bad and getting worse by the hour. Their expecting 12-18 inches or more. Thank God they just got a load of wood because their expecting power outage's due to freezing rain and ice also.
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220. CrazyDuke
11:35 PM GMT on February 13, 2007
Hi everyone. I finally decided to stop lurking.

Currently a radar indicated tornado visible on Intellicast's stormwatch thingy. 2 rotating storms near the GA\SC border.
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219. ryang
7:21 PM AST on February 13, 2007
Hey watch come to my blog!
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218. watchingnva
11:17 PM GMT on February 13, 2007
cell moving slightly south of east...people in brent need to be in shelter NOW!!!!!!!!!
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217. ryang
7:17 PM AST on February 13, 2007
I am good,yes looks bad as well.
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216. watchingnva
11:13 PM GMT on February 13, 2007
hey ryang, how u doing....looks to be a defiannt twister on the ground just nw of brent, al...
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215. ryang
7:11 PM AST on February 13, 2007
Hello Watch.
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214. watchingnva
11:08 PM GMT on February 13, 2007
the alabaster area needs to be getting prepared as well...
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213. Thunderstorm2
11:04 PM GMT on February 13, 2007
I've got to go. Stay safe everyone here and in Birmingham.
Member Since: December 22, 2006 Posts: 130 Comments: 7608
212. watchingnva
11:06 PM GMT on February 13, 2007
Cell A4 has severe rotation...people north of brent need to get to shelter immediatly...
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210. Thunderstorm2
10:56 PM GMT on February 13, 2007
It won't be a big all nation sport unless baseball size hail stones falling everywhere at once
Member Since: December 22, 2006 Posts: 130 Comments: 7608
208. Thunderstorm2
10:54 PM GMT on February 13, 2007
Damage-a plenty
Member Since: December 22, 2006 Posts: 130 Comments: 7608
207. ryang
6:52 PM AST on February 13, 2007
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206. Thunderstorm2
10:51 PM GMT on February 13, 2007
At maybe some pads CB
Member Since: December 22, 2006 Posts: 130 Comments: 7608
203. Thunderstorm2
10:48 PM GMT on February 13, 2007
Its getting worse up north but it's all over here
Member Since: December 22, 2006 Posts: 130 Comments: 7608

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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