Guest post by Steven Goddard
In my May 1st piece, Dr. Walt Meier at NSIDC hypothesized that differences in algorithm between NSIDC and NANSEN (NORSEX) were causing the gap between the NSIDC interpretation of normal and the NANSEN interpretation of normal, as seen below. They use different baseline periods which introduces some difference – but the discrepancy should go the other way due to the fact that the NANSEN base period (1979-2007) includes more low ice extent years from the current decade.
So I tried an experiment to test this out, where I overlaid NANSEN on top of NSIDC for the entire winter – and found that they are nearly identical. This would tend to discount the theory that differences in the algorithm are to blame. It appears from this more likely that one or the other has an error in their historical database which is affecting the interpretation of “normal.” Dr. Meier has stated that he is confident about the accuracy of the NSIDC database.
Using a third reference point, I tried another experiment comparing NSIDC (blue) vs. AMSR-E (red) and did see something interesting. Starting in late March, NSIDC (in blue) began to show more ice than AMSR-E (in red) – which uses a different satellite.
Last winter, the SSM/I satellite used by both NSIDC and NANSEN began to degrade, as reported by NSIDC and WUWT (of course.)
The degradation caused the ice extent to appear lower than AMSR-E, but now the problem seems to be going the other way – with SSM/I showing more ice than AMSR-E. What does it all mean? Given that NSIDC and NANSEN seem identical this year, I don’t think this explains the discrepancy in their baseline. It does appear that there is still an error in the SSM/I data however.
UIUC has quit posting their SSM/I images because the quality has become so bad.
February 25, 2009 – The SSMI images for many days in 2009 were bad enough that we removed them from this comparison display (see note below and the NSIDC website). There is enough interest in these side-by-side comparison images that we will try to replace them with corresponding images from the AMSR-E sensor in the coming weeks.
i wonder if we can get an answer from Meyers?
Makes me wonder what other satalites are breaking down?
Any developing problems with the SST measuring satalite (like the notorious bering sea hotspot in the NOAA charts), what about the one that gives us global average temps?
If you can’t trust GISS and the current satalites start to have problems like the one that measures sea ice, maybe it’s time we have new cutting edge technology take the stand and get the best possible data, what do you think?
Since were looking at the various lines wondering where they come from….
I have one question. What is casuing the bump in each trend at the start of June?
My own calculations from the raw gridded data showed that the arctic is currently well above the mean. My mean included the whole 79-09 record.
http://noconsensus.wordpress.com/2009/05/03/global-sea-ice-nears-record-high/
My data is considered preliminary from the NSIDC but the NOAA satellite causing the problem is removed and NOAA 13 is in its place. I don’t understand how my own mean can be that much higher but I believe it’s correct.
To my knowledge not too many others outside of paid climatology have worked independently from the raw gridded sets.
NSIDC released their update on April Arctic Sea Ice Extent today:
http://nsidc.org/arcticseaicenews/
It seems reasonably factual and starts out with the obvious, “Arctic sea ice extent declined quite slowly in April; as a result, total ice extent is now close to the mean extent for the reference period (1979 to 2000).” it also mentions that, “The decline rate for the month of April was the third slowest on record.”
It seems that they may be hoping that, “The thin spring ice cover nevertheless remains vulnerable to summer melt.”, but they may be reading the updates by the Catlin team versus the PAM-ARCMIP Polar 5 mission. Time will tell who’s right…
Adam from Kansas (18:46:55) : If you can’t trust GISS and the current satalites start to have problems like the one that measures sea ice,
Since GISStemp use simulated temperatures for the arctic that are based on sea ice estimates, I would speculate that the satellites screwing up the sea ice estimates also screw up GISStemp anomalies…
Barry L 18:50:55
That is the standard time for switching to a slightly different algorithm for calculating the values, because the summer has a greater amount of standing water on top of ice, which can confuse the sensors.
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What I’d like to know is why they count ice in the Sea of Okhostk as “Arctic Sea Ice Extent” and is not inside the Arctic Circle or connected in any way to the Arctic or even the Bering Sea… This is really a huge trick they use to gin up melting of the “arctic” when it really isn’t. What can we do to make a stink about this?
Just for grins, I did a Google search of “2009 record snow” and got:
Results 1 – 10 of about 11,000,000 for 2009 record snow. (0.24 seconds)
Here, you try it. Somehow I don’t think we’re having a snow shortage…
Even if some percentage of those 11 million pages are things where the 2009 is not a year marker, there is still a lot of snow falling somewhere…
what Barry said.
When Dr. Meier mentioned “differences in algorithm,” I assumed it mean -historical- differences, not current differences. Because the current data are very visually similar.
IOW: How does the 1979 data for the two methods compare?
Here is a nice comparison of where the NH sea ice extent in 2009 is compared to other years (from 1979 to 2009) and the two lowest minimum sea ice extent years (2008 and 2007) and the two highest minimum sea ice extent years (1980 and 1996).
This chart uses the NasaTeam algorithm which is slightly different than the current algorithm used by the NSIDC but it still gives a nice overall picture of the situation.
2009 is pretty close to the average right now (but there is still a lot of time left before the minimum extent happens around September 10th).
http://img377.imageshack.us/img377/6448/dailyseimay3.png
What are the possibilities that certain satelite detectors are more susceptible to cosmic rays?
WRT REF: http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png
Q1. When will the MSM start reporting that Arctic ice is at a 7 year high?
Q2. Isn’t the CATLIN team about to answer all our questions about the health of the Arctic Ice? – Well arn’t they???
You’d have to get his name right, then maybe…
There are a lot of factors that make it likely that the May report will show less melting than average
1) The report discusses the average for the month. All reports of this kind are inherently stale — by the time the data is published you know whether the month finished strong or weak. This gives you a lot of advance notice on the following month. We already know the data through May 3rd and May got a really high start.
2) The sea ice deficit (relative to the 79-00 average) in the sea of Okhotsk will disappear and will not affect the sea ice in other areas.
3) The weather forecast for Barrow, AK is NOT GOOD for melting sea ice.
http://www.weather.com/outlook/health/skin/tenday/USAK0025?from=36hr_topnav_skin
and, you’re welcome for the cute beach scene at the top. Really makes you think of Barrow, eh?
Since were on the topic of comparing graphs, the AMSR-E graph clearly shows that the April AVERAGE sea ice for 2003 was higher than 2009. (Compare the dark blue line to the red)
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
But NSIDC says other wise.
http://nsidc.org/images/arcticseaicenews/20090504_Figure3.png
WUWT?
Dr. Meier needs to check his data. In the published .txt data , there are missing data points (not many, but a couple) it skips from 1987-1989 at least twice. They need to go back and validate what they publish.
Briefly, from my earlier comment on the Mayday – May Day! post:
http://wattsupwiththat.com/2009/05/01/mayday-may-day/#comment-124916
Perhaps, in December 2008, when NANSEN seems to have adjusted their algorithm and posted a change to their ice data effective 22 October, they also massaged the data back to 11 September and then stopped. Might it be possible that if they had taken the time to go back through all their older data that their average would be lower than it is now?
In other words, what if the NANSEN 1979-2007 average itself is the problem, that it is based on a faulty way of measuring the ice that wasn’t corrected until December 2008, and only the data back to 11 September was corrected and none earlier? Seems a stretch I know, but what if no one really looked at the way they were doing things until last year when the NANSEN ice extent line was coming up on their mean and only then did they notice a problem with their data processing procedures.
Speculation is easy; only the folks in Norway know for sure.
Even if you can not select any dates from 2009 on Cryosphere today you can still compare the latest pictures with the ones in the past by modifying the web link manually.
In this link I maually typed in 2009 instead of 2008 on the 2nd image and got access to 2009-05-03:
http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=05&fd=03&fy=2008&sm=05&sd=03&sy=2009
And as they say, the quality on them is poor.
By the way. Dr. Meier, needs to look at the trend calculation. Last month…it showed a “-2.7% decline per decade”…an ever increasing gain the past year… Yet all of a sudden…with an above average daily GAIN the past month…now he is showing a -2.8% decline for March. He needs to review the data. How can bouncing ABOVE last year’s data for the month of March, now equate to losing the upward trend?
Am I missing something? Please correct me by pointing me to the rigth data series they publish as .txt files. I converted to Excel to plot my own trend which does not agree with theirs.
Frederick Michael (20:09:19) I assume you mixed your dates and meant that 2009 is greater than 2003, and it appears so in both graphs you link to.
Mike Strong (20:31:04) :
… How can bouncing ABOVE last year’s data for the month of March, now equate to losing the upward trend?
The April trend should be less steep in 2009 than it was last year, as the new point is a high one. But comparing April to March isn’t so simple. Expect the trend to get steeper as we go into summer. The melting the last few years was greater in the summer — and the denominator in the % calc is smaller then too.
Mike Lorrey (19:36:30) :
Perhaps you should insist they be more consistent in their terminology. At http://nsidc.org/data/seaice_index/daily.html they use the phrases “Northern Hemisphere (Arctic)” and “Southern Hemisphere (Antarctic)”. In the 1970s sea ice formed between Cape Cod and the islands of Nantucket and Marth’s Vineyard one year. In order to have that counted the next time it happens, I suggest you insist that NSIDC measure all Northern Hemisphere ice. Since that’s what they do, everyone will be happy.
Leon Brozyna (20:15:35) :
Briefly, from my earlier comment on the Mayday – May Day! post:
http://wattsupwiththat.com/2009/05/01/mayday-may-day/#comment-124916
Perhaps, in December 2008, when NANSEN seems to have adjusted their algorithm and posted a change to their ice data effective 22 October, they also massaged the data back to 11 September and then stopped. Might it be possible that if they had taken the time to go back through all their older data that their average would be lower than it is now?
They didn’t change their data at all, here’s the before and after graphs (it blanks back and forth between the graphs):
http://wattsupwiththat.files.wordpress.com/2008/12/nansen_sea_ice_extent1-520.gif
However on the second graph which compares this graph with the mean the latter part of the graph was in error (and therefore didn’t match the above curve). At the date in question the latter graph was corrected and thereafter matched it’s partner. It’s unclear to me why an error in fall 2008 would effect the 1979-2007 average in any case, however since the base data was unchanged that’s moot.
Steve Keohane (20:41:56) :
Frederick Michael (20:09:19) I assume you mixed your dates and meant that 2009 is greater than 2003, and it appears so in both graphs you link to.
I make lots of mistakes but not this time. For the month of April, the dark blue line starts way above the red line but ends below. On average, the blue line (2003) is higher. However, the NSIDC comparison (of averages) shows 2009 just a hair higher. That’s why I wondered what’s up.
By the way, the differences are so tiny, it may not be all that mysterious.