Arctic climate change: the past 100 years

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

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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

References

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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103. hurricane23
4:01 PM EST on February 12, 2007
On radar you can see things will begin to clear up rain wise in the next couple of hours.Off and showers are still possible later on tonight across southeast florida.
Member Since: May 14, 2006 Posts: 8 Comments: 13632
102. Thunderstorm2
8:55 PM GMT on February 12, 2007
Well................
Member Since: December 22, 2006 Posts: 129 Comments: 7608
101. Jorick23
8:39 PM GMT on February 12, 2007
The rain near Key Largo reminds me of the time a storm hit Ft. Lauderdale a little over a year ago. I was in a travel trailer in a trailer park. A 3 hour downpour started. First hour, 2"/hr. Second hour, 3"/hr. Third hour, 5" per hour. 10 inches total, with a tornado touching down a half mile away. The water made it up to the top of my hubcaps and another 2 inches would have brought it into my trailer. Next morning all the water was gone, but it sure left a mess!
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100. hurricane23
3:39 PM EST on February 12, 2007
There's definately a spin there but nothing of great importance.

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99. Skyepony (Mod)
8:32 PM GMT on February 12, 2007
Member Since: August 10, 2005 Posts: 161 Comments: 37424
96. Skyepony (Mod)
8:17 PM GMT on February 12, 2007
100% chance 1.5" hail in west TX. LA your next. This front so far has beentrending toward big hail.
Member Since: August 10, 2005 Posts: 161 Comments: 37424
95. Thunderstorm2
8:17 PM GMT on February 12, 2007
Ok skye
Member Since: December 22, 2006 Posts: 129 Comments: 7608
94. Skyepony (Mod)
8:08 PM GMT on February 12, 2007
Warm or cold core systems need a core~ which this doen't have at least not yet. Warm core has the rain closer to the middle in a more round shape, cold core doesn't mean less, just not so gathered in the middle ~ the ukmet I had posted has it going, once it's part of the noreaster, asymentric warm core which is like subtropical...picking up some warmth from the gulf stream. Jeff has had blogs on these before, they're not tropical, just winter storms feeding off & strengthening temperarly from the warm gulf stream. Warmth means potental strength, not percipitaion.
Member Since: August 10, 2005 Posts: 161 Comments: 37424
92. weatherboykris
8:11 PM GMT on February 12, 2007
I was wondering if more rainfall occurs in warm core systems than it does in cold core systems?


I think that probably depends on the situation, CB.
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91. Thunderstorm2
8:08 PM GMT on February 12, 2007
If that storm was happining in HS then it may have been something to watch but since we are not in HS then it's just a bunch of clouds that are crying to much
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90. Skyepony (Mod)
8:06 PM GMT on February 12, 2007
The only thing warm there is a warm front. Key
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88. hurricane23
3:06 PM EST on February 12, 2007
Were i placed the circles is were the heaviest rainfall has occured close to land.
Member Since: May 14, 2006 Posts: 8 Comments: 13632
87. weatherboykris
8:04 PM GMT on February 12, 2007
Rainfall rates like that 15"+,do they mean warm core?


What does rain rate have to do with core temperatures?
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86. hurricane23
3:05 PM EST on February 12, 2007
Incredible amounts indeed.
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85. weatherboykris
8:04 PM GMT on February 12, 2007
yes TS2.it is 15+ inches.
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83. Thunderstorm2
8:01 PM GMT on February 12, 2007
Is the light blue that is circled indicating that there has been 15 inches of rainfall in that area? if it is HOLY!!
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82. hurricane23
3:01 PM EST on February 12, 2007
Here is a radar image showing accumulated rainfall.

Member Since: May 14, 2006 Posts: 8 Comments: 13632
81. Thunderstorm2
7:58 PM GMT on February 12, 2007
They were calling for La Nina by late summer in the weekly report. Thats what i don't think is BS for once
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80. weatherboykris
7:57 PM GMT on February 12, 2007
And i don't think thats aload of BS



What is?
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79. Skyepony (Mod)
7:54 PM GMT on February 12, 2007
The UKMET on the 12Z run just goes off on the noreaster, feeding bad on the gulf stream.
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78. Thunderstorm2
7:56 PM GMT on February 12, 2007
And i don't think thats aload of BS
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77. weatherboykris
7:55 PM GMT on February 12, 2007
They were calling for La Nina by late summer in the weekly report.



They're finally waking up.
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76. Thunderstorm2
7:52 PM GMT on February 12, 2007
(Whistles Loudly and longly) WOW H23 that alot of water
Member Since: December 22, 2006 Posts: 129 Comments: 7608
75. Skyepony (Mod)
7:49 PM GMT on February 12, 2007
ENSO took another slide, currently conditions are neutral, looked like a .2 for the 3&4 region. It's gone down so quick it's probibly gonna take March or april to get a 3 month average below .5 to make it offically over. They were calling for La Nina by late summer in the weekly report.
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74. weatherboykris
7:53 PM GMT on February 12, 2007
I'm presuming cold.
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72. Thunderstorm2
7:48 PM GMT on February 12, 2007
True
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71. hurricane23
2:48 PM EST on February 12, 2007
Thunderstorm2 theres areas in the keys that have recieved near 9 inches of rainfall.
Member Since: May 14, 2006 Posts: 8 Comments: 13632
70. Skyepony (Mod)
7:40 PM GMT on February 12, 2007
kris~ the black are rain contaminated, though that is the high resolution. It was near 5 hrs old too.

Hail is picking up in TX, some widely scattered along that line to TN. Interesting weather day.
Member Since: August 10, 2005 Posts: 161 Comments: 37424
69. hurricane23
2:45 PM EST on February 12, 2007
Predicted numbers are not something to focus on cause even a quite season can turn out ot be a very bad one.It only takes one to ruin lives. Steering patterns will determine everything come late july into early august.Till then its a wait and see game.Adrian
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67. weatherboykris
7:45 PM GMT on February 12, 2007
He asked a question TS2.I answered him.
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66. Thunderstorm2
7:45 PM GMT on February 12, 2007
How much rainfall have you got so far H23
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65. Tazmanian
11:44 AM PST on February 12, 2007
Jorick23 or they can send it to me we could ues some of it
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64. Thunderstorm2
7:43 PM GMT on February 12, 2007
Taz,the numbers say that El Nino is over and we are neutral.A La Nina is on the way.

Well it's been on the cards since Early January
Member Since: December 22, 2006 Posts: 129 Comments: 7608
63. Tazmanian
11:42 AM PST on February 12, 2007
weatherboykris rats i want my 90L oh well i wait for the next one
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62. hurricane23
2:42 PM EST on February 12, 2007
0 chance Taz just alot of rainfall for me.
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61. weatherboykris
7:41 PM GMT on February 12, 2007
sorry Taz,but it won't be 90L.
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60. Thunderstorm2
7:41 PM GMT on February 12, 2007
Thats alot of cloud cover with some battering rains,i hear
Member Since: December 22, 2006 Posts: 129 Comments: 7608
59. weatherboykris
7:40 PM GMT on February 12, 2007
Taz,the numbers say that El Nino is over and we are neutral.A La Nina is on the way.
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58. Jorick23
7:35 PM GMT on February 12, 2007
Taz, All they have to do is pile it up in a field somewhere and make a ski area out of it.

Or they could ship it here to NH. We're still waiting for snow.
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57. Tazmanian
11:39 AM PST on February 12, 2007
could it be comeing 90L???? been waiting a long time for 90L to pop up you think this have a ch or may be a small ch
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56. hurricane23
2:38 PM EST on February 12, 2007
No significant developemnt of any kind is expected but a weak surface low is somewhat possible.Movement off all this should be northward.Looks quite rainy the next 12-18 hours for southeast florida.

Member Since: May 14, 2006 Posts: 8 Comments: 13632
55. HadesGodWyvern (Mod)
7:37 PM GMT on February 12, 2007
See the latest Mesoscale Discussion concerning a mixture of sleet, freezing rain, and snow for S. Nebraska and Northern and Central Kansas.

this discussion also includes East Central Colorado.
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54. Thunderstorm2
7:37 PM GMT on February 12, 2007
Good Afternoon Everyone. How are you all today?
Member Since: December 22, 2006 Posts: 129 Comments: 7608
53. Tazmanian
11:34 AM PST on February 12, 2007
ok sky i see now
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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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