NSIDC issues documentation corrections – WUWT guest post a catalyst

You may recall the guest post from Jeff Id of the Air Vent I carried about a week ago called Global Sea Ice Trend Since 1979 – surprising

In that post, a note of correction was issued because that we were led to believe (by Tamino) that the entire post was “invalidated” due to an error in accounting for ice area very near the pole. Both Jeff and I were roundly criticized for “not reading the documentation”, which was one of the more civil criticisms over there at Tamino’s site.

After further investigation It turns out that the error was in NSIDC’s public documentation, and they have issued a correction to it. Even more importantly the correction now affects NSIDC’s own trend graph, and they are considering how to handle it.

This episode illustrates how citizen science can be useful. Sometimes people too close to the science they publish can make mistakes, (we’ve all been there) which is why peer review of papers is important.  But “web review” in this day and age of instant publication is equally important.  It also illustrates how mistakes, however embarrassing initially, can be useful if you learn from them and study the cause.  There is no shame in mistakes if they are corrected and you learn from them.  But, the blogospheric noise of angry and sometimes juvenile criticism (on both sides) really isn’t useful as it often masks the real issue. The key is to put that aside and find the truth behind the error. Jeff has done that. His update follows below.

Merry Christmas to everyone!  – Anthony

Based on The Air Vent post carried by Watts Up With That, the National Snow Ice Data Center has issued several corrections to the documentation of their sea ice area time series.

Guest post by Jeff ID

Most will remember my earlier post which plotted global sea ice trends. After initially concluding that the global ice level wasn’t decreasing measurably Tamino pointed out a problem in my analysis. After issuing my corrections, thanks and apologies to Tamino and the um…..thousands of readers of Watts Up With That, I went back to work investigating what was really happening to the ice area time series.

It was actually quite lucky that Tamino mentioned the step in the data and criticized me for not reading carefully (something which was mentioned in several comments on the various threads). When I first learned of it, I found the criticism was based on an entirely different set of ice area data with different source documentation. Still, I checked closely and found the tiny step in the time series and was convinced that I had missed something. I had spent a huge amount of time learning the data before I made my post so it was frustrating to say the least. Understand, I used several resources to check my work; not the least of which was the National Snow Ice Data Center (NSIDC) anomaly graph which has the same shape as the one I generated.

The first graph below is from the NSIDC website, the second is my calc. Differences in the noise between the two are explained by the daily resolution used in my graph compared to what my eyes tell me must be monthly data for their plot. They also seem to have an additional year (2007) in their data plot which is not available in the bootstrap time series I used.



After reading everything with great care, this graph and a similar one for the SH were used to verify my results before my original post. This paragraph below used to be on the NSIDC website describing the data of these time series.

In computing the total ice-covered area and ice extent, pixels must have an ice concentration of 15 percent or greater to be included; thus, total ice-covered area is defined as the area of each pixel with at least 15 percent ice concentration multiplied by the ice fraction in the pixel (0.15-1.00). Total ice extent is computed by summing the number of pixels with at least 15 percent ice concentration multiplied by the area per pixel. Sea ice concentrations are assumed to be 100 percent around a circular sector centered over the Northern Hemisphere pole (known as the pole hole) which is never measured due to orbit inclination. The Southern Hemisphere also has a pole hole; however, it does not affect this sea ice data set; since only land is under this hole. For SMMR, the hole is 611 km in radius and is located poleward of 84.5 degrees north. For SSM/I, the hole is 310 km in radius and is located poleward of 87 degrees north.

After checking this for about the hundredth time along with the rest of the extensive documentation, I wrote to the NSIDC and asked them to confirm that the area anomaly for the NH wasn’t corrected another way. Several emails back and forth later they confirmed that the area anomaly wasn’t accounted for. I then pointed out that the graph above and the paragraph in the data description were in error. After a short time, the NSIDC replied that they had their sea ice team was reviewing the data and planning an immediate update to their site.

That same day the site was corrected to read:

In computing the total ice-covered area and ice extent with both the NASA Team and Bootstrap Algorithms, pixels must have an ice concentration of 15 percent or greater to be included. Total ice extent is computed by summing the number of pixels with at least 15 percent ice concentration multiplied by the area per pixel, thus the entire area of any pixel with at least 15 percent ice concentration is considered to contribute to the total ice extent. Total ice-covered area is defined as the area of each pixel with at least 15 percent ice concentration multiplied by the ice fraction in the pixel (0.15-1.00). There is a circular section over the Northern Hemisphere pole (known as the pole hole) which is never measured due to orbit inclination. For the purposes of ice extent, pixels under the pole hole are always considered to be at least 15 percent. For total ice-covered area, the pixels under the pole hole are not used. The Southern Hemisphere also has a pole hole. However, it does not affect this sea ice data set because there is only land under this hole. For SMMR, the hole is 611 km in radius and is located poleward of 84.5 degrees north. For SSM/I, the hole is 310 km in radius and is located poleward of 87 degrees north. Note: The difference in pole hole areas between SMMR and SSM/I results in a discontinuity in the Northern Hemisphere ice-covered area time series across the instrument transition.

Link HERE. They are still considering how to handle the area anomaly graph.

Since this changes how you interpret area data substantially, there is no easy method for updating the trend graph. Still, the step in the data is quite small as shown below.


It occurs right after 1987.5 which corresponds to the 87 July/August boundary which is different from tamino’s reference. If we assume worst case that the NH hole in the data was 100% filled with ice (it wasn’t), the calculation from before produces a slight downslope in comparison to the flat trendless line in my original post. The result is only a trend equaling a 4% reduction in global sea ice over a nearly 30 year period. Not exactly disastrous either way. I am going to continue my work on this by matching (regressing) the last two years from other sites on the end of the data. With the recent global cooling, it should be interesting to see where global sea ice is today.

I need to offer thanks to Anthony Watts for putting the original post on his blog. His professionalism was commendable in handling this matter quickly and transparently. IMO this openness to correction is lacking on several AGW blogs. I also need to thank the NSIDC (particularly, Dave, Molly and the Sea Ice Team) who really blew me away with their responsiveness and professional demeanor in making these corrections.


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John Cooper

Good work. Merry Christmas, y’all!


Thanks for the analysis. Always good to see the reporting agency so open with their data and analysis. Compare the NSIDC response here to several other recent data and documentation issues covered here and at CA.


Is it right to say due to this change in calculating ice area, the data in the ice anomaly plots prior to 1978 should be bumped up 0.3 M km^2, which would level out the plot a lot and remove the step up in ice area between 1987 and 2000?


Merry Christmas!

Thanks for the great work and Merry Christmas.
I watch the cryosphere religiously but with the trends I don’t expect the trend to break across the satelllite record ‘average’ (anomaly from ’78 to 2k means) until the end of the season and probably there won’t be huge changes to ‘colder’ historical norms until the Atlantic Oscillation goes cold as well (like the Pacific) in a couple of years.
In the mean time watching the temperatures in Siberia is telling (as in another story). I’ve worked in that weather and its has its challenges in what construction materials you can use. Wood is pretty safe 😉 common material.
Once again thanks for keeping everyone honest and keeping contrast to the leviathon of GIGO in this discussion. Give me Raw Data and First Principles Analysis. … or a close approximation 😀


Jeff – great job, and judging by the extreme comments often found on your blog – I can’t imagine staying sane at times with the very personal attacks directed towards you.
This transparency is what is lacking in too many AGW endeavors and is a major factor in questioning it’s foudnation. Not a GISS slam, but they should take a lesson here, make the One Who’s Name Shall Not Be Spoken’s task deciphering their arcane “system” much easier – and the smoke blanketing so much of this controversy would blow away.
Merry Christmas all – time to go shovel yet more of the global warming accumulating in my driveway.

Apparently Hansen doesn’t hold much sway over the NSIDC folks. Good on ’em for responding in such a timely and professional manner. Great work, Jeff. It will be extremely interesting to see your graph once you’ve punched in the 2008 data. (And AGW heads will be exploding everywhere, which will make 2009 even more fun than 2008 has been on the Global Warming Cooling front!)

Steve Keohane

Regarding another popular depiction of NH ice, I spent a little time on Cryosphere the other day and noticed something odd in comparing 12/20/80 to 12/22/80 NH ice extent. Hudson Bay and the outlet of Ob river in Russia, the boot-shaped inlet next to the arctic, appeared larger in the 1980 plat. I took the landmass/shoreline from 1980 and overlaid it on the 2008 plat, and got this: http://i44.tinypic.com/330u63t.jpg
The Arctic and Bering Seas appear to have been encroached upon, ie. made smaller. The white adjacent to the shoreline is the current snow/shoreline, and shows the loss of available ‘sea’ area for ice. I think that the representation of the river Ob’s outlet is more realistic on the 2008 shoreline, but previously a much greater extent of ice was measured there. There are extensive areas off eastern Russia that used to be measured for ice extent but now are designated ‘snow’, as is much of the shoreline of the whole arctic. This next blink comparison is four images, 12/20/1980, 9/22/2008, 12/20/1980, and 12/22/2008. I chose 9/22 as a minimum ice & snow image to maximize the modern shoreline. This allows the examination of the old shoreline with the modern shoreline of 9/22 and the modern snowline of 12/22. I hope this is all a change in accounting for the ice to make it more realistic, but can’t help but wonder if it is only another in a long list of biases to exaggerate the effect of AGW. If the latter is true, the ice extent can never be what it once was. http://i39.tinypic.com/b7f4fc.jpg
Please note that I retained the star background in all images, and used their pixels for image registration. At full size, I see no perturbation of those pixels from one image to the other, and therefore assume they are correctly registered. Merry Christmas to all from a deeply white western Colorado, 80″ so far this Dec. on Aspen Mtn., more to come tomorrow and the weekend.
Expect to break all records.


It is nice when professionals act professional. Particularly after seeing the run around some scientists give people asking questions about their work.


And I suppose that Tamino will post a retraction.

Jeff Alberts

Jeff, did NSIDC credit you with uncovering their mistake and notifiying them?
Did Tamino apologize?
Whoa, wait a second, what was I thinking??

P Folkens

Will apologies begin to flow from Tamino and the others who excoriated Jeff and Anthony from the get-go? Integrity is important and appears to be in abundance on WUWT. What Tamino and his ilk say about the essence of today’s WUWT post will go far in determining the nature of their integrity. Silence will also be telling.
From what one can tell from the US Senate race in Minnesota and the Illinois’ second Senate seat problem, integrity and “transparency” in Washington will not improve going forward as the Gore/Pelosi/Democrat global warming agenda comes to the front. Time to be very concerned, if not afraid.
OT, but in keeping with the Christmas theme: did you hear about snowglobes contributing to warming? Apparently, giant snowglobes can ignite nearby combustibles.

Steve Huntwork

As a long time meteorologist, I can recognize when something simply does not “smell right.”
You have done the professional thing and checked your data. That is all that anyone could ask from you.
Well done!


I guess this is why it is so useful to have critics on both sides. How long would the error have persisted if no one was looking?

Mike Bryant

Steve Keohane,
That is great work. Even if they do not use those comparison “photos” to calculate sea ice area or extent, they obviously create an erroneous impression and should be immediately corrected. Looking at your first overlay, I find myself wondering how this could be inadvertant. Still I hope when CT sees this they will act quickly to put it straight.
Mike Bryant

Mike Bryant

Steve Keohane,
Just eyeballing the map at the top of this page it seems there may be an additional problem. It appears besides encroaching on the sea ice areas with the snow, that someone also may have encroached the sea and sea ice areas onto the land on the earlier “photos”. To check this might be difficult, but if I am correct it would effectively double the possible difference between the old and new. I copied your previous comment to CA, hope you don’t mind.

John McGeough

Very interesting stuff.
I know several people have commented on the flattening of the curve of ice extent since Dec.10th. I’m having trouble believing its real. At the same time the picture of ice extent from the sat photos has shown visible ice growth off the east coast of Russia, and temperatures there have been very cold. I’m not sure how the absolute amount of ice could remain the same if what I think I am seeing is real. Has ther been ice loss elsewhere?
Can someone explain this apparent discrepancy to me?

“4% global ice shrinkage in 30 years”
Is that a statistic I can really take away from all of this?

Yup, that’s the worst case trend. The instantaneous (today) number is a different thing.

Thanks to everyone, and Merry Christmas.

Layman Lurker

In fairness to Tamino, he did point out a legitimate oversight – one which ultimately led to Jeff’s follow through with NSIDC. Jeff rightly aknowledges Tamino for this. I don’t think it is fair to say that Tamino unfairly attacked Jeff or that he owes Jeff any apology. Tamino in fact commended Jeff for the manner which the oversight was handled on his part. In light of the circumstances I think Tamino’s statement about the entire post being invalid was an over the top statement given the circumstances (the error was more glaring for NSIDC – would he have so boldly stated that NSIDC’s arctic temp anomaly graph was “invalid”? Doubtful). Commentaters at Tamino’s open thread #9 were definitely quick to jump on Jeff and some ridiculed him for being careless and reckless in his oversight. Jeff tried to clarify on the thread that hours of scouring the NSIDC site could uncover no mention of the 1987 step. Not a real flattering portrayal of “problem solving” by pro AGW commentaters but as Anthony says it happens on both sides of the debate.


This episode illustrates how citizen science can be useful.
Ditto that. There is too much the notion that science — and in particular climate science — is so esoteric that one must belong to a select group of peers in order to have anything valid to say.
Good work, Jeff and Anthony.

Jack Simmons

This is the web at its very best.
Someone points out what they think is an error, and the authors respond with adjustments.
I like it when I visit a website knowing the people there really do care about accuracy.
Just wonderful.
Thanks Anthony for facilitating this type of thing.


I’m confused. Your graphs show a step up in ice area going from July to August 1987. Doesn’t that make the ” real” downward trend larger?

> This episode illustrates how citizen science can be useful.
> Sometimes people too close to the science they publish can
> make mistakes, (we’ve all been there) which is why peer review
> of papers is important. But “web review” in this day and age of
> instant publication is equally important.
It is precisely this methodology which has allowed Open Source (e.g. the linux kernel and the many Open Source applications that run under it) to quickly mature into a threat to Microsoft’s dominance. A particularly applicable saying from the Open Source world is “With many eyes, all bugs are shallow”. I would love to see scientific papers subjected to this same review.

I guess I’d have to see the formulas to understand how the error evolved. The description wasn’t fully clear to me. Good job, though, really fine work all around.
And kudos (kyo̵̅o̅′däs′) to Dave, Molly and the NSIDC Sea Ice Team for their responsiveness and scientific stamina.
OT: I think that Arctic land-sea interface change has been mentioned elsewhere about 5 to 6 months ago, but I’m not sure where or by whom.


Thanks for your persistence and dedication, Anthony. Merry Christmas and Happy New Year to you and all your readers.

Bill Illis

It seems to me there are still big discrepancies that need to be explained.
1995 is the year that sticks out to me. It used to be the record low year but that record disappeared in the spring of 2007 when the historic data record was rewritten.
But it now reappears in your data Jeff. Bill Chapman explained the change as there was missing days in 1995 and in some other years (mainly 2002 and onward of course since the trend was drastically revised downward).
I’m assuming there is no missing days in your data Jeff. Any ideas?
Before and after animation of the changes made in the spring of 2007.

global temperature
For a previously unknown aspect of change in global temperature, see:


Bill Illis: Can you add an empty 2008 record to the first graph so the graph wriggles less during the 2007-2008 flicker?


P Filkens
I certainly don’t know where you are getting your information about the Minnesota Senate election but you are very ill informed. Election integrity is something I have studied seriously for years. Minnesota’s system is a a model for the rest of the country. It has an auditable system unlike most. I wish my state had such a system. When you have paper ballots that citizens can count by hand, there is no better system. Period.
The recount in Minnesota was required by law and by hand count. It has been extremely transparent to the point of even a newspaper putting questionable ballots on a website for the entire public to view.
Come on. It doesn’t get any more transparent than this.

George E. Smith

If I’m not mistaken, the election was held around seven weeks ago.
There’s been enough time for people to hand copy each and every ballot form handed in in Minnesota. It’s the same old story ;there are political operatives who can reverse any election if you just give them enough time to keep recounting the votes and rehandling the forms.
This is like Florida 2000 all over again. The florida law said what a valid vote consited of, and the recounters kept making up new rules after the election was all over.
Minnesota’s ballot form was designed to be machine readable if voters voted correctly as they were instructed to. anything the machines can’t read, should be tossed as not clearly indicating the voter’s preference as provided in the instructions.
Is there a pattern here, that one party can be counted on to have plenty of dummy’s who can’t follow the simplest instructions; these recounts always seem to drift in just one political direction; as in Government by the dumbest.

Steven Hill

Kentucky has the best voting system in the USA, end of story! First to have results for 2008 election.


Bill Illis:
Have a look at the maps for Sep 30 and Oct 1 1995. Something weird happens there. Suddenly large areas of ice appear in the White Sea, James Bay, Norton Sound, Kotzebue Sound, the Sea of Okhotsk and even the Baltic. Now there simply isn’t any ice in any of those places in early October, so obviously those areas are spurious. If those areas were discounted in the pre-spring 2007 version, but included in the more recent version there might be a jump in the anomaly.
One more thing – it seems that Wrangels land was considered as being sea ice in 1995.

Mike Bryant

I know this video shows anecdotal evidence, but the more interesting thing to me is the reaction of the videographer to the situation he is witnessing. Especially since it happened in Seattle.


“Even more importantly the correction now affects NSIDC’s own trend graph, and they are considering how to handle it.”
In what way? Does the new corrected NSIDC trend show more melting or less?


Merry Christmas all – time to go shovel yet more of the global warming accumulating in my driveway.
They’re shoveling global warming in Louisiana. (Patton was right.)

Tim L

Something is going on here. Look these are black people in snow.
look at the palm trees! they just don’t tolerate cold.

I under stand that snow fall does not mean lower temps but please,
we are talking snow on desert type land!
REPLY: It was pea sized hail from a thunderstorm system that blanketed the area. – Anthony


Thanks for the update, Anthony and Jeff. I’m in the Lower Mainland of British Columbia, and we have about two feet of snow on the ground where I live. That breaks records going back almost 40 years. Merry Christmas and Happy Holidays everyone!

And I search Tamino’s weblog in vain for a reference to Ian Joliffe. Does anyone know what happened to it?


No Matter What Happens, Someone Will Blame Global Warming ?!?
Global warming was blamed for everything from beasts gone wild to anorexic whales to the complete breakdown of human society this year — showing that no matter what it is and where it happens, scientists, explorers, politicians and those who track the Loch Ness Monster are comfortable scapegoating the weather.
FOXNews.com takes a look back at 10 things that global warming allegedly caused — or will no doubt soon be responsible for — as reported in the news around the world in 2008.
1. Cannibalism
In April, media mogul Ted Turner told PBS’s Charlie Rose that global warming would make the world 8 degrees hotter in 30 or 40 years. “Civilization will have broken down. The few people left will be living in a failed state, like Somalia or Sudan, and living conditions will be intolerable,” he said.
Turner blamed global warming on overpopulation, saying “too many people are using too much stuff.”
Crops won’t grow and “most of the people will have died and the rest of us will be cannibals,” Turner said.
2. The Death of the Loch Ness Monster
In February, Scotland’s Daily Mirror reported that 85-year-old American Robert Rines would be giving up his quest for Scotland’s most famous underwater denizen.
A World War II veteran, Rines has spent 37 years hunting for Nessie with sonar equipment. In 2008, “despite having hundreds of sonar contacts over the years, the trail has since gone cold and Rines believes that Nessie may be dead, a victim of global warming.”
3. Beer Gets More Expensive
In April, the Associated Press reported that global warming was going to hit beer drinkers in the wallet because the cost of barley would increase, driving up the price of a pint.
Jim Salinger, a climate scientist at New Zealand’s National Institute of Water and Atmospheric Research, said Australia would be particularly hard hit as droughts caused a decline in malting barley production in parts of New Zealand and Australia. “It will mean either there will be pubs without beer or the cost of beer will go up,” Salinger said at a beer brewer’s convention, the AP reported.
4. Pythons Take Over America
Giant Burmese pythons – big enough to eat alligators and deer in a single mouthful – will be capable of living in one-third of continental U.S. as global warming makes more of the country hospitable to the cold-blooded predators, according to an April report from USAToday.com.
The U.S. Geological Survey and the Fish and Wildlife Service investigated the spread of “invasive snakes,” like the pythons, brought to the U.S. as pets. The Burmese pythons’ potential American habitat would expand by 2100, according to global warming models, the paper reported.
“We were surprised by the map. It was bigger than we thought it was going to be,” says Gordon Rodda, zoologist and lead project researcher, told USAToday.com. “They are moving northward, there’s no question.”
5. Kidney Stones
A University of Texas study said global warming will cause an increase in kidney stones over the next 30 years, the Globe and Mail reported in July.
Scientists predict that higher temperatures will lead to more dehydration and therefore to more kidney stones. “This will come and get you in your home,” said Dr. Tom Brikowski, lead researcher and an associate professor at the University of Texas at Dallas. “It will make life just uncomfortable enough that maybe people will slow down and think what they’re doing to the climate.”
6. Skinny Whales
Japanese scientists, who have claimed that the country’s controversial whaling program is all in the name of science, said in August that if they hadn’t been going around killing whales, they never would have discovered that the creatures were significantly skinnier than whales killed in the late 1980s, the Guardian reported in August.
The researchers said the study was the first evidence that global warming was harming whales by restricting their food supplies. As water warmed around the Antarctic Peninsula, the krill population shrank by 80 percent as sea ice declined, eliminating much of the preferred food of the minke whale.
The whales studied had lost the same amount of blubber as they would have by starving for 36 days, but the global warming connection couldn’t be proven because no krill measurements are taken in different regions.
7. Shark Attacks
A surge in fatal shark attacks was the handiwork of global warming, according to a report in the Guardian in May.
George Burgess of Florida University, a shark expert that maintains an attack database, told the Guardian that shark attacks were caused by human activity. “As the population continues to rise, so does the number of people in the water for recreation. And as long as we have an increase in human hours in the water, we will have an increase in shark bites,” he said.
Shark attacks could also be the result of global warming and rising sea temperatures, the Guardian said. “You’ll find that some species will begin to appear in places they didn’t in the past with some regularity,” Burgess said.
8. Black Hawk Down
Although it happened in 1993, the crash of a U.S. military helicopter in Mogadishu that became the film “Black Hawk Down” was blamed on global warming by a Massachusetts congressman in 2008.
“In Somalia back in 1993, climate change, according to 11 three- and four-star generals, resulted in a drought which led to famine,” Rep. Edward Markey told a group of students who had come to the Capitol to discuss global warming, according to CNSNews.com. “That famine translated to international aid we sent in to Somalia, which then led to the U.S. having to send in forces to separate all the groups that were fighting over the aid, which led to Black Hawk Down.”
9. Frozen Penguin Babies
Penguin babies, whose water-repellant feathers had not grown in yet, froze to death after torrential rains, National Geographic reported in July.
“Many, many, many of them—thousands of them—were dying,” explorer Jon Bowermaster told National Geographic. Witnessing the mass penguin death “painted a clear and grim picture” of global warming.
“It’s not just melting ice,” Bowermaster said. “It’s actually killing these cute little birds that are so popular in the movies.”
10. Killer Stingray Invasion
Global warming is going to drive killer stingrays, like the one that killed Crocodile Hunter Steve Irwin, to the shores of Britain after a 5-foot -long marbled stingray was captured by fishermen, the Daily Mail reported in June.
A single touch can zap a man with enough electricity to kill, the Mail said, and global warming is bringing the Mediterranean killers north.
“Rising sea temperatures may well have brought an influx of warm water visitors,” sea life curator Alex Gerrard told the Mail. “Where there’s one electric ray, it’s quite likely that there are more.”


This is the kind of post that makes this site worth visiting. Thanks.
Merry Christmas!


OT…but here’s a great new business opportunity, and if we hurry, we can get in on the ground floor.
“Travelers will enter their destination into the kiosk, which will calculate the amount of carbon dioxide for which they are responsible and the cost of offsetting it. After swiping their credit cards, they would get a receipt listing the exact carbon-reducing projects their money went to.”
Wonder what the overhead is per transaction…

J. Peden

Steve Keohane, thanks and nice sleuthing even if it doesn’t pan out:
The white adjacent to the shoreline is the current snow/shoreline, and shows the loss of available ’sea’ area for ice.
But if this discrepancy holds up as an example of further tomfoolery in the practice of “Climate Science”, is it too much to hope that now I can say I’ve finally seen everything? Or at least until that Alan Abel media-hoaxster guy pulls off his next stunt?
-If sea area is decreasing, are the Oceans actually disappearing as a result of AGW?


Don’t know if anybody has posted this yet but according to the NSIDC, this years ice extent area is now less than 2007-2008 area.
Seems kind of odd how all of a sudden, the line flattens out…
REPLY: Yes it does seem odd. But since nobody seems to have a clear picture as to why, I’m not going to speculate. It will shake out, patience. – Anthony

James A

Why does the NSIDC highlight the arctic ice extent data and not have the antarctic ice extent data readily available? Is this purely political or is their organization not the “home” of that data and thus not highlighted on their website?
Also, if they should have both, why is there not a chart with worldwide ice extent (sea ice, glaciers, snow cover, etc.)

Steve Keohane

Mike Bryant (11:45:29) I agree that the sea/ice interface encroached on land, as the inlet for the river Ob is huge on the ’80 plat relative to the ’08 plat, and to the actual inlet. I am sure their are other areas as well. I had a typo in my post, I ment “12/22/08” instead of “12/22/80”.

Pamela Gray

Sea ice area and extent needs average range bars. This should be easily calculated. I wonder why it isn’t? Could it be that most years fall within the average range of sea ice area and extent? Some graphs that depict actual data include the average range. Anomaly graphs use 0 as a line without an average anomaly range. I think this is done to enhance the idea that “sea ice is below the mean so we should panic”.

Pierre Gosselin

Merry Christmas!
Don’t know about you, but to me it appears the latest SST point to a La Nina in the works: Compare to 3 months ago.
No wonder Seattle is freezing over!


Any comments… “I’m confused. Your graphs show a step up in ice area going from July to August 1987. Doesn’t that make the ” real” downward trend larger?”
BTW the current sea ice flat line is easy to explain. Its been really warm in those regions where sea ice should be growing at this time of year – that’s the north Pacific and North Atlantic. This is just a local exaggeration of the above average temperatures the near surface of the northern hemisphere has been experiencing in recent months (4th warmest November on record).