Claim: Antartica record high sea ice partially an artifact of an algorithm

From the European Geosciences Union

Tabular iceberg surrounded by sea ice in the Antarctic

Tabular iceberg surrounded by sea ice in the Antarctic (Credit: Eva Nowatzki, distributed via imaggeo.egu.eu)

New research suggests that Antarctic sea ice may not be expanding as fast as previously thought. A team of scientists say much of the increase measured for Southern Hemisphere sea ice could be due to a processing error in the satellite data. The findings are published today in The Cryosphere, a journal of the European Geosciences Union (EGU).

Arctic sea ice is retreating at a dramatic rate. In contrast, satellite observations suggest that sea ice cover in the Antarctic is expanding – albeit at a moderate rate – and that sea ice extent has reached record highs in recent years. What’s causing Southern Hemisphere sea ice cover to increase in a warming world has puzzled scientists since the trend was first spotted. Now, a team of researchers has suggested that much of the measured expansion may be due to an error, not previously documented, in the way satellite data was processed.

“This implies that the Antarctic sea ice trends reported in the IPCC’s AR4 and AR5 [the 2007 and 2013 assessment reports from the Intergovernmental Panel on Climate Change] can’t both be correct: our findings show that the data used in one of the reports contains a significant error. But we have not yet been able to identify which one contains the error,” says lead-author Ian Eisenman of the Scripps Institution of Oceanography at University of California San Diego in the US.

Reflecting the scientific literature at the time, the AR4 reported that Antarctic sea ice cover remained more or less constant between 1979 and 2005. On the other hand, recent literature and the AR5 indicate that, between 1979 and 2012, Southern Hemisphere sea ice extent increased at a rate of about 16.5 thousand square kilometres per year. Scientists assumed the difference to be a result of adding several more years to the observational record.

“But when we looked at how the numbers reported for the trend had changed, and we looked at the time series of Antarctic sea ice extent, it didn’t look right,” says Eisenman, who set out to figure out what was wrong.

Scientists have used satellite data to measure sea ice cover for 35 years. But the data doesn’t come from a single instrument, orbiting on a single satellite throughout this period. Instead, researchers splice together observations from different instruments flown on a number of different satellites. They then use an algorithm – the most prevalent being the Bootstrap algorithm – and further processing to estimate sea ice cover from these data.

In the study published in The Cryosphere, Eisenman and collaborators compare two datasets for sea ice measurements. The most recent one, the source of AR5 conclusions, was generated using a version of Bootstrap updated in 2007, while the other, used in AR4 research, is the result of an older version of the algorithm.

The researchers found a difference between the two datasets related to a transition in satellite sensors in December 1991, and the way the data collected by the two instruments was calibrated. “It appears that one of the records did this calibration incorrectly, introducing a step-like change in December 1991 that was big enough to have a large influence on the long-term trend,” explains Eisenman.

Difference between sea ice cover in two datasets (Credit: Eisenman et al., The Cryosphere, 2014)

To measure sea ice cover, researchers splice together observations from different instruments flown on a number of different satellites. They then use an algorithm – the most prevalent being the Bootstrap algorithm – and further processing to estimate sea ice cover from these data. A new The Cryosphere study compares two datasets for sea ice measurements: one generated using a version of Bootstrap updated in 2007, and another that results from an older version of the algorithm. Subtracting the older dataset from the new one, shows a spurious jump in the satellite record in December 1991. The vertical dotted lines indicate transitions between satellite sensors, with the December 1991 change dominating the difference in ice cover in the two versions. (Click image for higher resolution.) Credit:Eisenman et al., The Cryosphere, 2014

“You’d think it would be easy to see which record has this spurious jump in December 1991, but there’s so much natural variability in the record – so much ‘noise’ from one month to the next – that it’s not readily apparent which record contains the jump. When we subtract one record from the other, though, we remove most of this noise, and the step-like change in December 1991 becomes very clear.”

With the exception of the longer time period covered by the most recent dataset, the two records were thought to be nearly identical. But, by comparing the datasets and calculating Antarctic sea ice extent for each of them, the team found that there was a stark difference between the two records, with the current one giving larger rates of sea ice expansion than the old one in any given period.

If the error is in the current dataset, the results could contribute to an unexpected resolution for the Antarctic sea ice cover enigma.

###

This research is presented in the paper ‘A spurious jump in the satellite record: has Antarctic sea ice expansion been overestimated?’ to appear in the EGU open access journal The Cryosphere on 22 July 2014.

The scientific article is available online, free of charge, from the publication date onwards, at http://www.the-cryosphere.net/recent_papers.html. *A pre-print copy of the paper is available for download at http://www.egu.eu/news/118/is-antarctic-sea-ice-cover-really-setting-record-highs/*.

The team is composed of Ian Eisenman (Scripps Institution of Oceanography, University of California at San Diego, USA), Walter Meier (NASA Goddard Space Flight Center, USA) and Joel R. Norris (Scripps).

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C.M. Carmichael

So much for settled science, they can’t even agree on the math.

A

Oh, give it a rest!!!

Quinx

Funny how none of the *warming* is attributed to such problems.

Oh gee, now a model refutes itself.

Anto

Next, I expect that they will investigate the US land temperature reports from GISS and NCDC and discover that they are all an artifact….or not.

Unfortunately for these researchers, there is no visible step in the Antarctic sea ice anomaly circa 1992. In fact, the graph is unusually flat during this period. On the other hand, starting around 2011, the graph shoots up at an uncharacteristically high rate. The error they describe cannot have produced this.

chris moffatt

“our findings show that the data used in one of the reports contains a significant error. But we have not yet been able to identify which one contains the error,” says lead-author Ian Eisenman
Surely they are joking. “there must be an error somewhere but we couldn’t find it” now merits publication in a Science journal? Color me contemptuous…..
Here’s a thought – perhaps increasing antarctic sea-ice is due to the fact that the planet isn’t warming. See – no error needed.

Bloke down the pub

So they’ve been reporting too much ice? Maybe the Arctic death spiral actually happened and you could now sail across an ice-free North Pole? I think I’ll let someone else go first and check before I try sailing it.

whi3981m

If there *was* a jump in late 1991, Pinatubo could be the explanation.

This implies that the Antarctic sea ice trends reported in the IPCC’s AR4 and AR5 [the 2007 and 2013 assessment reports from the Intergovernmental Panel on Climate Change] can’t both be correct…
But isn’t AR5 supposed to be an update of AR4?

captainfish

I’m confused. If the error in 1991 caused a negative bias to the anomaly, then shouldnt the overall trend from then on be negative? Shouldn’t we see an issue with the data in 1992 if the error was in 1991? But, we don’t see an increase until 1993.

JimS

I thought the increase in Antarctic sea ice wasn’t very important anyway. Scientists said so, so it must be true. The important thing is that “we melted the Arctic.” We know that is true too, because a scientist said so.

Wait! Wait!
Maybe we all need to sit down and take a breath.
A team of researchers have found what appears to be an error in the IPCC’s AR5 report!
I’m gobsmacked!

John Peter

Maybe they should now look at the “jump” in sea levels when they went from tide gauges to satellite measurements without having a multiyear overlap to verify the conversion. They could also look at some of the NOAA and GIStemp adjustments that Steven Goddard thinks he has revealed. Come to think of it Hadcrut 3 to 4 as well. Amazing when nature will not comply with current CAGW beliefs somebody comes riding to assistance with the heat has gone to the Arctic/deep ocean (take your pick), the sea ice is not there after all. Wrong algorithm and on it goes. We have just had the pause is actually just a natural variation and the warming will soon continue again, but not natural (CO2 driven you understand).

R Babcock

“A team of scientists say ..” Bill Nye, the science guy and Kermit the Frog are leading the team. The deflector shields must be up.

North of 43 and south of 44

Gee a possible programming error?
Let me count the ways, oh hell ISTR a study (you know about them, correct?) that there is approximately 3 mistakes (of various kinds) per 100 LOC. This is one reason you keep getting millions of bytes of patched code all the time. I installed 66MB of such this morning.
Who would have thought that them being scientists and all.
/major sarc

ConfusedPhoton

If observations do not agree with the models, then these observations must be wrong. Lets “harmonise” them to make them fit.
Well folks that’s climate “science” for you!

ren

There is none of discontinuity, and certainly since 2011.’m Not surprised that the article is free.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

Mark

This really shows how incompetent they are. They can’t identify the cause of the difference between two algorithms because the data is too noisy? How about they actually look at the codes and understand what they are doing (especially the most common mistakes associated with integer maths)? It also suggests at the huge amount of data massaging going on…

Scute

“The most recent one, the source of AR5 conclusions, was generated using a version of Bootstrap updated in 2007, while the other, used in AR4 research, is the result of an older version of the algorithm.”
Notice how the date of the older version isn’t cited (although it may be buried in the supplementary material). If the previous version of Bootstrap was drawn up in the 1990’s then it could be argued that it was biasing low in its representation of sea ice due to CAGW political pressure. This could be achieved by biasing the parameters of the model. This would mean that the 2007 version of Bootstrap is the faithful representation and the old version was a victim of wishful thinking or political pressure to bias low. I’m not suggesting foul play but a subconscious urge to tow the line.
The last paragraph here confirms such a biased view because they are clearly hoping it is the 2007 version that is wrong and that the sea ice trend is flat:
“If the error is in the current dataset, the results could contribute to an unexpected resolution for the Antarctic sea ice cover enigma.”

David Rodgers

I wonder what that stuff was that the ship of fools was stuck in last summer then?

george e. conant

http://www.csmonitor.com/Science/2014/0721/Global-warming-How-2013-broke-records
http://mashable.com/2014/07/21/2014-hottest-june-on-record/
I hope these links work, anyways my thought here is of artifacts of data analysis and who is telling the truth. I haven’t seen anything about the truthfulness of these two reports …. seems fitting now that we are being that the Antarctic Sea Ice extant isn’t as big as we thought….

ren

Sea ice will be a record in late September because the temperature drops of the ocean around Antarctica.
http://weather.unisys.com/surface/sst_anom.gif

Darren Potter

“A team of scientists say much of the increase measured for Southern Hemisphere sea ice could be due to a processing error in the satellite data.”
Interesting how there are only “processing errors” when cooling is indicated…

george e. conant

ah, left out a word, “now that we are being told….”

Given the polar see-saw, it is a bit surprising that Antarctic ice is hitting a maximum while Arctic ice is increasing again. So the idea that the Antarctic measure is in error is at least a bit credible. But it is still disturbing that effort to find errors is still only being made when data goes against AGW.

North of 43 and south of 44

Mark says:
July 22, 2014 at 6:39 am
______________________________________
Mark I think they haven’t a clue as to what the possible errors could be.

Gary Pearse

Can’t we see this ice from satellites? Isn’t such a thing important enough to go down there and fly an observational sampling? You can see that the Antarctic ice has become very troubling to the committed. It was only a matter of time before they began to ‘correct’ it. Why do we have all these expensive Anarctic expeditions? If they can’t keep tabs on the ice, what in hell are they keeping tabs on???

Gary Pearse

I think sceptics are going to need a big fund to keep tabs on these guys. We need to have independent flights with photo and gps around the sea ice, or at least a number of transepts. Maybe there is enough coverage of the Ship of Fools incident to compare observed with measured in that area to check up on the health of the instrumentation.

Darren Potter

David Rodgers – “I wonder what that stuff was that the ship of fools was stuck in last summer then?”
Going by the SPIN of hyperventilating media;
It was a large floating Salt flat. Resulting from evaporation of sea water, caused by extreme heat of GW.
/sarc

James Strom

Remember that story about Prof. Chris Turney getting stuck in the ice? Never happened. Data processing error.

Darren Potter

Gary Pearse: “I think sceptics are going to need a big fund to keep tabs on these guys.”
Quite the opposite. We need to CUT the funding of all the GW Climatologists.
Wouldn’t hurt to reset/reboot NASA, and cut E.P.A. down to a staff the size WattsUpWithThat has.

Jimbo

Ahh so Antarctica isn’t melting? Look chaps some fools argued that the increased extent was due to melting ice. So which is it? A slippery lot indeed.

So they aren’t sure and they haven’t found where the alleged fault is. So what, pray tell, was the point of this paper???

ren

There is no reason to call into question the data. The ice may temporarily fluctuate because of circulation.
http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/aao.obs.gif

Jimbo

We now need to investigate ALL the satellites for possible errors. Think Arctic et al.

Keith Gordon

Can we assume that the sea ice the Australian expedition that got stuck in, in the Antarctic last January, was imaginary and just an artifact of a computer programme? If not we should keep our eyes on these people, I see more adjustments coming and they will not show ice growth. I am all for getting accurate data but adjustments so far are nearly always in one direction.
Regards
Keith Gordon

Neil

Mike Jonas says:
But it is still disturbing that effort to find errors is still only being made when data goes against AGW.

I thought AGW was the null hypothesis… anything that supports the null hypothesis doesn’t need investigating.

Another climate data error, another adjustment in the favorable direction. It is beyond curious that climate data adjustments never favor an “it’s not as bad as we thought” direction, isn’t it?

ossqss

Amazing this is being put forth a week before arctic ice extent is forecast to go above normal for the first time since 1996.
Coincidence, I think not.

SunSword

Simple enough way to validate. Start a ship at a known GPS point 1 mile off Antarctic coast. Circumnavigate Antarctica until return to GPS starting point staying 1 mile distant from ice all the way around. Subtract distance from circumference to ice (1 mile). Calculate area from distance of calculated circumference.

StuartMcL

So let me get this straight.
We’re talking about a single step of considerably less than 0.2 million sq km in 1991 (based on eyeballing the graph). That would make the 1979 – 2008 mean, at most, 0.1 million sq km higher.
Current anomaly is more than 1 million sq km above the mean. . An order of magnitude larger than the discrepancy in the mean.
And they claim that this step accounts for “much of the measured expansion ” and has “large influence on the long-term trend”?
Pull the other one, it’s got bells on.

Chris4692

David Johnson says:
July 22, 2014 at 6:56 am

So they aren’t sure and they haven’t found where the alleged fault is. So what, pray tell, was the point of this paper???

Others using the data or previous papers depending on the data can be aware that there may be a problem and adjust their research accordingly. Plus this way they get two publications on their CV’s: one announcing the error and one announcing the fix.

Green Sand

Any talk about Antarctic Sea ice expansion and the year 2007 crops up.
NOAA Reynolds Sea Surface Temperature anomalies (rel to 1971 to 2000)for 60 to 70 South from Jan 2000 to Jun 2014:-
http://nomad1.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?ctlfile=monoiv2.ctl&ptype=ts&var=ssta&level=1&op1=none&op2=none&month=jan&year=2000&fmonth=jun&fyear=2014&lat0=-70&lat1=-60&lon0=-180&lon1=180&plotsize=800×600&title=&dir=
Circa 2007 there is an almost “step change” as the anomalies went into negative territory and apart from a couple of months have stayed there since. Latest value Jun 2014 = -0.29C.
NOAA Reynolds says the waters down there are “cooler” than “normal” and have been for circa 7 years.

John Davis

This error is stupidly insignificant. Look at the vertical axis of their tell-tale graph. The “error” represents a shift in Antarctic ice extent of 0.2 million sq km. The increase in sea-ice extent as I write is 1 million sq km over the long term average, and it has in the recent past been as high as 2 million sq km. So at best, they’ve accounted for less than 20% of the increase, probably nearer 10%.
It’s the implicit dishonesty of presenting this as an “explanation” of the high sea ice area that really dismays me. It’s not even slightly convincing, and everyone involved must have realised that. Gun… foot…

AnonyMoose

Arctic sea ice loss can’t be due to an algorithm problem, so let’s not study that.

hunter

But the excuse for the record expansion is that the modles predicted it.
Watch the climate obsessed turn on a dime if it turns out there is less ice and claim that any reduction was predicted as well.

TomRude

The noise -even if the error is insignificant- will be enough for the MSM to play its prop role…

Dusan Ristic-Petrovic

It seems to me that the ‘step change’ – if there was one – affected both poles so that when Antarctic ice apparently grew, Arctic ice shrank. Perhaps the mysterious error affects both poles, albeit in an opposite sense. The authors’ not considering this possibility looks like confirmation bias favoring AGW-friendly hypotheses.

Johan

Reality changes as the algortithms change? We must be living in the matrix after all.