The pole star and Arctic climate change

By: Dr. Jeff Masters , 05:01 PM GMT am 15. Februar 2007

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Hello Weather Underground bloggers, Aaron here. Dr. Masters is on vacation so I'll be posting a series of vacation blogs for him. This is the first.

In my previous blog, I mentioned how the Arctic Climate Impact Assessment (ACIA), a 2004 study of Arctic climate compiled by 300 scientists over three years, found that the recent increase in Arctic temperatures was probably due to human-emitted greenhouse gases. Greenhouse skeptics attacked the ACIA report and its conclusion, pointing out that the Arctic was much warmer than today during the period 4,000 - 7,000 years ago. For example, Dr. Patrick Michaels said in a 2004 interview with CNS news, a conservative Internet news service:"It was warmer 4 to 7,000 years ago [in the Arctic.] Every climatologist knows that. I saw no mention of that in the Arctic report," Michaels said. He added that the past warming of the Arctic couldn't possibly be blamed on greenhouse gas emissions since it occurred long before the industrial era.It is true that Arctic summers were warmer during the period 4,000 - 7,000 years ago. The mean July temperature along the northern coastline of Russia may have been 2.5 to 7.0 �C warmer than present, and Scandinavian summer temperatures were 1.5 to 2 �C higher than at present. The warming was caused by changes in the amount of sunlight the north pole gets in summer due to variations in the Earth's orbit.
Figure 1. Summertime temperatures in the Arctic during the Mid-Holocene Warm Period (about 6,000 years ago), compared to today's temperatures. Image credit: NOAA.

Earth's orbital variations
Earth's orbit is not perfectly circular, which means that we are closest to the sun in December and farthest in July. Thus, the Southern Hemisphere gets more sunlight in their summer (December) than the Northern Hemisphere does in their summer (July). The Earth's current 23.5 degree tilt keeps the north pole pointed towards the star Polaris, which results in the north pole being pointed at the sun in December (Northern Hemisphere winter). The Earth slowly wobbles around its axis with a period of 23,000 years a href=(precession) so that the pole star gradually changes with time. During the period 4,000 - 7,000 years ago, the pole star was Thuban in the constellation Draco, and the north pole was pointed at the sun during Northern Hemisphere summer. This resulted in much warmer summer temperatures in the Arctic, since there was more summer sunlight. Conversely, winter temperatures were colder, since the Earth was farther from the sun during the Northern Hemisphere winter. The Arctic will again be much warmer in summer 16,000 to 19,000 years from now when the cycle repeats and Thuban is once more the pole star. The reason the ACIA failed to mention this climate period is that the average temperature in the Arctic remained about the same during the period 4,000 - 7,000 years ago; it was just the summers that warmed. The warming since 1980 and the 1930s were warmings over all seasons, so it was misleading for the climate skeptics to compare Arctic temperatures 4,000 - 7,000 years ago with these modern warmings.

This is the second in a series of five blogs on climate change in the Arctic that will appear every Monday and Thursday. Next blog: Why the Arctic sea ice is shrinking.


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

Jeff Masters

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275. hurricane23
1:19 PM EST on February 19, 2007
Good afternoon,

Watching Favio with winds currently at 65kts with futher intensification possible.Damage with this cyclone could end up being rather extensive if favio continues to strengthen futher then forcasted.


Member Since: Mai 14, 2006 Posts: 8 Comments: 13719
274. Skyepony (Mod)
3:42 PM GMT on February 19, 2007
flood~ I read this lastnight~ Said the thermohaline belt has slowed~ expects atleast another 25%-50% drop in the next 100 years. In that time we could expect greater warming due to green house gasses & well the warm water gets stuck here. Didn't think the major brunt would hit til after 2100, though highly uncertain...you probibly won't get to see it.
Member Since: August 10, 2005 Posts: 162 Comments: 37820
272. HIEXPRESS
10:07 AM EST on February 19, 2007
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CST MON FEB 19 2007

VALID 221200Z - 271200Z

MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT CONCERNING THE DEVELOPMENT
OF A VIGOROUS UPPER-LEVEL TROUGH OVER THE WRN U.S. EARLY IN THE
PERIOD. AS THE LARGE UPPER-LEVEL TROUGH APPROACHES THE CNTRL U.S.
FRIDAY...LOW-LEVEL MOISTURE WILL STREAM NWD INTO THE PLAINS AND
OZARK REGION SETTING THE STAGE FOR A SEVERE WEATHER EVENT FRIDAY
AFTERNOON AND FRIDAY NIGHT. A LARGE NUMBER OF STRONG THUNDERSTORMS
WILL LIKELY DEVELOP ACROSS THE MS VALLEY ON SATURDAY AND WIDESPREAD
SEVERE WEATHER WILL BE POSSIBLE AS THE SYSTEM MOVES INTO THE OH AND
TN VALLEYS SATURDAY NIGHT. IN ADDITION...THERE IS A POTENTIAL FOR
SEVERE WEATHER ACROSS NRN FL AND THE SRN PART OF THE ATLANTIC
SEABOARD SUNDAY AS THE SYSTEM MOVES INTO THE ERN U.S.

..BROYLES.. 02/19/2007
Member Since: Oktober 13, 2005 Posts: 4 Comments: 2156
271. wtherdrk
9:02 AM EST on February 19, 2007
though i only skimmed most of the comments, i find it odd that no one commented about the speed in which this temperature spike took place. the event 4-7000 years ago, not only was caused by astronomy and other natural events, but was also over a period of 3000 years and innacurate (summers warmer, but winters colder). this recent temperature spike was within 50, and all year. THAT'S scary, and indicative evidence of greenhouse gasses.
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270. biff4ugo
8:01 AM EST on February 19, 2007
Dr. M told us Aaron was going to do these blogs a few weeks ago. Nice point there Aaron about the wobble and over all annual temperature. It was nice to see that the American (academy of sciences?) finally caught up with the rest of the world on global warming in the news this morning.
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269. HurricaneRoman
1:58 AM GMT on February 19, 2007
It was windy here in S. florida and much colder than usual.. a few lose shingles from the hurricanes flew off today
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268. Thunderstorm2
6:06 PM GMT on February 18, 2007
Good Evening?
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
267. Thunderstorm2
6:02 PM GMT on February 18, 2007
I've got to go for a late lunch
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
266. ryang
1:58 PM AST on February 18, 2007
Good Evening all.
Member Since: August 25, 2006 Posts: 329 Comments: 12429
265. Thunderstorm2
5:26 PM GMT on February 18, 2007
Anyone on?
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
264. HIEXPRESS
12:07 PM EST on February 18, 2007
Because it it way too cold here near Orlando, I post this link to a video of a pilot doing his darnedest to give us some CO2/GW to help us out.
Video
Boss, the plane
Member Since: Oktober 13, 2005 Posts: 4 Comments: 2156
263. lightning10
4:07 PM GMT on February 18, 2007
I am one who hides from the spring/summer sun. Where I am 90's and 100's become a daily thing. I dont have AC so I become very inactive during the season. I also work extra hours without getting payed just cause there is AC there. (I am an assistent administrator for a high school)
Member Since: November 24, 2005 Posts: 41 Comments: 630
262. tornadodude
4:07 PM GMT on February 18, 2007
well ,talk to y'all later...
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261. tornadodude
3:58 PM GMT on February 18, 2007
So Cal is dry and hot, indiana is snowy, florida is cool, and all is gradualy warming as spring draws near...
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260. lightning10
4:00 PM GMT on February 18, 2007
O ok :).

Yes I noticed a slow down in the blogs this month.
Member Since: November 24, 2005 Posts: 41 Comments: 630
259. lightning10
3:58 PM GMT on February 18, 2007
With the exception of the cold snap in So Cal back in January (coldest in 10 years) it has been quite a borning winter in So Cal.
Member Since: November 24, 2005 Posts: 41 Comments: 630
258. tornadodude
3:56 PM GMT on February 18, 2007
not you lightning, but there is no one on here.
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257. tornadodude
3:56 PM GMT on February 18, 2007
boring...
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256. lightning10
3:53 PM GMT on February 18, 2007
El Nino didnt bring me any rain. I wonder if there will be a wierd mix where La Nina brings us buckets. ITs been so dry here in So Cal we have nothing to lose at this point. El Nino wasnt doing anything besides setting up a blocking ridge and causing winds to kick up in the passes and canyons.

I know in So Cal around every 1/3 El Ninos are dry but near record setting dryness.
Member Since: November 24, 2005 Posts: 41 Comments: 630
255. tornadodude
3:29 PM GMT on February 18, 2007
Statement as of 7:49 am EST on February 18, 2007


... 12 inches of snow on the ground at Indianapolis...

The snow depth at 700 am EST for Indianapolis was 12 inches. This is
the first time that snow depth at Indianapolis has reached 12 inches
in 25 years. The last time a 12 inch or higher snow depth was
observed at Indianapolis was 12 February 1982.

Snowfall records began at Indianapolis in 1884.


hey guys... perty interesting..
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254. Thunderstorm2
1:46 PM GMT on February 18, 2007
Well it should be interesting
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
253. hurricane23
1:38 PM GMT on February 18, 2007
Hey guys!

I think the key isssue is now to see if la nina does indeed develope.In my opinion we could see a moderate to weak la nina come time for hurricane season around july-august time frame.The next australian update is feb 21.
Member Since: Mai 14, 2006 Posts: 8 Comments: 13719
252. pottery
9:33 AM AST on February 18, 2007
The forecast for el nino to mid-may were based on information to hand then. I've been saying for a while, that we are basing our predictions on data that is out of sync because we dont have all the relevant data.Research has to be done to find the data that helps to control these phenomena. Historical data is boo because we've never been here before.
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24236
251. Thunderstorm2
1:34 PM GMT on February 18, 2007
Hi H23
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
250. pottery
9:31 AM AST on February 18, 2007
Good Morning 23.
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24236
249. Thunderstorm2
1:30 PM GMT on February 18, 2007
El Nino is gone? So much for the forecast of El Nino lasting untill Mid May. HA
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
248. Thunderstorm2
1:28 PM GMT on February 18, 2007
Strange!?!?! It's weird. I have never seen a state nearly split down the middle by seperate weather Warnings.
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
247. hurricane23
1:29 PM GMT on February 18, 2007
Neutral Conditions are now in place....

Current Conditions
As of mid-February 2007 conditions indicate that the El Nio event has ended. SSTs are currently observed to be approximately 0.5C above average in the parts of the equatorial Pacific, particularly near the dateline. In the ENSO relevant regions of the central/eastern equatorial Pacific SST anomalies have declined considerably since their peak values in December 2006. Cold SST anomalies have developed in the eastern Pacific, reaching approximately -1.0C below average near 125W. The deep, or downward, thermocline perturbations in the eastern Pacific, associated with the El Nio event, have been replaced over the past month with shallow anomalies. The upwelling Kelvin wave associated with the shallow thermocline anomalies originated in the off-equatorial western Pacific, and has been slightly amplified by large-scale easterly wind anomalies since late December. These easterly wind anomalies are also helping to draw these subsurface temperature anomalies toward the surface, resulting in the localized cold SST anomalies. Currently the thermocline is shallower than normal across most of the equatorial Pacific, and the Trade Winds have been anomalously easterly.

MORE HERE
Member Since: Mai 14, 2006 Posts: 8 Comments: 13719
246. pottery
9:25 AM AST on February 18, 2007
Good point, Cafeinhog.......
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24236
245. pottery
9:19 AM AST on February 18, 2007
Hi Storm2. Strange weather indeed. Cold thunderstorms ? Could it be that the weather is changing ? I wonder how come .

On a different note, No, Im not realy trying to figure out the steering current set-up, and your post that we were just insulting each others intelligence could not have refered to me, since I dont have any. Especialy not this morning............LOL
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24236
244. Caffinehog
1:16 PM GMT on February 18, 2007
Yes, but is this change in upwelling a new phenomenon? Or has it been going on for millions of years? The article implies that it is new, but does not directly state it, and gives no evidence that it hasn't happened before. Would we even KNOW if it happened 100 years ago? Or would fishermen just think that they had a bad year?
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243. Thunderstorm2
1:15 PM GMT on February 18, 2007
G'Morning Pottery.

It's not warm here.

North and Central Florida is split down the middle by two warnings, on the Left a Freeze Warning and on the Right a Red Flag Warning.
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
242. pottery
9:03 AM AST on February 18, 2007
Good Sunday Morning . Its a hot one !
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24236
239. Skyepony (Mod)
5:08 AM GMT on February 18, 2007
PUBLIC INFORMATION STATEMENT...UPDATED
NATIONAL WEATHER SERVICE MELBOURNE FL
845 AM EST FRI FEB 16 2007

UPDATED TO RAISE NUMBER OF FATALITIES IN TORNADO 1

(click on link for complete statement)

Member Since: August 10, 2005 Posts: 162 Comments: 37820
237. ryang
9:38 PM AST on February 17, 2007
STL Please help move this blog,RICDEAR.
Member Since: August 25, 2006 Posts: 329 Comments: 12429
235. Caffinehog
1:34 AM GMT on February 18, 2007
NellyStormGeeks is a troll. Ignore him. He posted similar stuff earlier, and has nothing intellegent to say.
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233. Skyepony (Mod)
10:04 PM GMT on February 17, 2007
Gfs & comrades are so undecided on that low yet. Things look like they probibly will get interesting, end of next week or the weekend but the where, when & how interesting are unknown.
Member Since: August 10, 2005 Posts: 162 Comments: 37820
232. Skyepony (Mod)
9:56 PM GMT on February 17, 2007
rlwalker~ CO2 is a big problem, this in no way says it isn't, this shows that we are near a peak of a natural cycle. When you consider what we've done with CO2 at the peak of the hot phase in the natural cycle & how CO2 amounts & temp relate, then one can see a little more of how crazy an experiment we are putting our enviroment through.
Member Since: August 10, 2005 Posts: 162 Comments: 37820
231. weatherboykris
10:00 PM GMT on February 17, 2007
Well you're Mr. Sunshine,huh STL?LOL,I've got to go,too.
Member Since: Dezember 9, 2006 Posts: 125 Comments: 11346
229. Thunderstorm2
9:42 PM GMT on February 17, 2007
I've got to go. Bye everyone
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
228. Thunderstorm2
9:35 PM GMT on February 17, 2007
Unless the snow and the rain mix. Sleet will fall
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608
226. Thunderstorm2
9:24 PM GMT on February 17, 2007
Your in for the 'Most BS Weather Ever' award STL
Member Since: Dezember 22, 2006 Posts: 129 Comments: 7608

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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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