From the European Geosciences Union
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.
“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.
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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).
The Antarctic extent seems to be rebounding from sudden decline in extent noted over the past few days.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.antarctic.png
Also, the Arctic’s uptick, shows on other graphs. I recall in a thread a few months ago on prediction of the Sept minimum extent and the NOAA model predicting a positive anomaly for this, a brief exchange with Greg Goodman in which I surmised that the exceptional amount of +2m ice would likely give a positive anomaly and that late season with ~1m thick of this ice surviving to become two year old ice. Greg was offering a much more (unnecessarily I thought) complex model.
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
This uptick may well be marking the approach to the edge of the more durable ice of the winter’s +2m thickness. It will be interesting to see if this simple common sense model has merit. Of course all bets are off if we get another August Arctic cyclone, but I don’t believe the weather is right for this. Heck most of our July has been 22C instead of ~28-30. Interestingly we have passed the halfway point for the ~70 days of plus temperatures north of 80N and the whole summer there has been cooler than average. Yeah, we are going to have a positive September extent anomaly.
http://ocean.dmi.dk/arctic/meant80n.uk.php
Himalaya: a mess
Amazon forrest drought: a mess
Models: a mess
Global temperatures: a mess
Consensus: a mess
OHC: a mess
Sea ice: a mess
Next?
When the Antarctic science teams can drive and walk across the ice to Antarctica the Global Warming Industry will still be playing the same tune.
“Arctic sea ice is retreating at a dramatic rate.” No, it ain’t. Cryosphere Today – no change in about ten years. Keep chanting it doesn’t make it true.
“if, could, may, possible, projected, implies, assumed…”
What do such weasel- words of the press release add to the conversation?
“C.M. Carmichael says:
July 22, 2014 at 6:07 am
So much for settled science, they can’t even agree on the math.
1. Talk to Roy Spencer about the difficulties in stitching together various sensors. UAH has
gone through numerous versions as Spencer and Christy try to figure out the best
set of ADJUSTMENTS to the raw sensor data. Sensors change. Platforms change,
2. Talk to Leif about the difficulties of stitching together various sensors measuring TSI
3. Talk to Leif about the difficulties of stitching together a resonable sunspot record from
many different observers using different counting techniques, changes in counting
methods and changing instruments.
4. Talk to Anthony. His latest paper uses series where the raw data has been corrected for
changes to instruments. .
Sensors in space do not measure temperature. They dont measure ice extent or area.
They measure brightness at the sensor at various frequencies. Those raw voltages are then
processed by models to create estimated “data” which try to represent things like temperature
of ice extent. The sensors change over time. The algorithms change.
People do agree on the math. 2+2 = 4. But when it comes to turning a raw voltage at the sensor
to a physical property… that’s more than simple math. It typically involves a physics model with
many assumptions.
Keep on the sunny side, always on the sunny side,
Keep on the sunny side of life;
You will feel no pain, as they drive you insane,
If you keep on the sunny side of life.
Sometimes you just have to laugh at this stuff
Ohhh, the desperation of it all. They are going to be in full retreat in a few years when every indicator turns against them They will all be under the hood wondering why none of the machinery is working.
But we’ve been given scientific explanations for why the Antarctic ice is increasing despite AGW. If it’s not actually increasing, that must mean that their explanations were.. no, I can’t say it ….
“chris moffatt says:
July 22, 2014 at 6:23 am
“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…..
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not uncommon for processing sensor data from a satellite.
1. You dont have a ground truth ( the actual sea ice extent ) to compare each method to.
2. The codes for generating an estimate of ice from the raw sensor data is very complex.
go read a ATBD.
This is an easy theory to test. Use the old algorithm to reprocess the records from 1978 to present. Then use the new algorithm over the same time period. There should be a constant offset between the two methods for the entire 35 years if the new method over-estimates ice extent. But that would mean they have to adjust older ice extent upward. Where have we seen that before;)
Ed says: July 22, 2014 at 8:07 am
But we’ve been given scientific explanations for why the Antarctic ice is increasing despite AGW.
Come on, give those guys a break. At least now they get to say: “It’s not as bad as we thought”.
Which proves yet again that there is no end to what these people don’t know about climate.
chris moffatt says:
July 22, 2014 at 6:23 am
“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…..
a religious journal, all that is required is faith in AGW, embrace them, don’t be deceived by mere skeptics 😉 /sarc
My reading on this if its worth anything: Some of the AGW funders are beginning to ask questions, re the pause, re Australia scrapping the tax and closing down all “AGW climate research”, re the ice expansions. Basically the climate scientists are grasping at straws to keep their jobs, after all, they too have families etc ( I can’t blame them, but dishonesty will further make their holes bigger), That is the hole they are digging themselves into LOL. BTW you can bet your XXX that most of the loudest ones are coming from Australian “Climate scientists”.
Cop: “You were accelerating past 80 in a 25 zone.”
Me: “Officer, your data biases you to believe that I was accelerating past 80 while I don’t feel that I was. Since your data and my blind faith to the contrary cannot both be correct, yours must contain an error that you have not found yet. Therefore, my faith trumps your empirical data. Have a good day, sir.”
….
….
….
Me: “…And that, your Honor, is how I found myself standing here in front of you.”
==============
Why are they allowed to use a silly assinine excuse and I am not? Their logic is just as stupid as my above scenario!
John Bills says:
July 22, 2014 at 7:47 am
Himalaya: a mess
Amazon forrest drought: a mess
Models: a mess
Global temperatures: a mess
Consensus: a mess
OHC: a mess
Sea ice: a mess
Next?
————————————-
Looks like we have a consensus.
Quinx says:
July 22, 2014 at 6:10 am
Funny how none of the *warming* is attributed to such problems.
Oh yes they did! When the satellite based MSU & RSS showed next to [no] warming, they seized upon altitude degradation errors unaccounted for, as well as minor instrument errors. However, when these were corrected it made very little difference to the overall data! Remember, they are never wrong, especially when they are wrong!
BTW its quite likely that the MOST vociferous AGW alarmists now, will become the most anti-AGW when they grow up in about 20 years.It happens regularly look at the ex Head of Greenpeace LOL
………is there any criteria for global warming that someone hasn’t said was wrong?
The paper is leading propaganda all the way through, and at almost every turn of phrase, starting from the title itself. It rhetorically asks: “has Antarctic sea ice expansion been overestimated?,” as if to hint at the correct answer. So why didn’t they ask if the possibility of sea ice extent previously being underestimated? The whole paper is like this. The words seem to agonize over not knowing which version of the Bootstrap algorithm is correct, but their implication is always on the interpretation most favorable to “the cause.” Nowhere is an acknowledgement that the newer version carries the assumption of being an improved version of the earlier version. Even though the documentation for the model shift is poor, there should be no presumption that the earlier model was superior. Never did they explore the notion that both versions could be incorrect. Nowhere was a discussion of how we might employ physical observation and testing to validate the newer and ostensibly, better, more correct algorithm. They only looked at the data sets produced by the algorithms themselves. If the algorithm change creates a potentially deceptive step change, which might be either spuriously creating, or righteously correcting, the ice extent record, then why isn’t the algorithm and it’s changes the whole point of the paper?
All that said, this closing paragraph captures the only thing you need to understand about this study, and it nicely summarizes the problems of climate science:
Not only should the data sets have version control, but the algorithms that generate those data sets should be version controlled and thoroughly documented as well. I’ve long railed for these kinds of improvements to science in the internet era. I know this is a big issue for Steve McIntyre, too. Science, like real estate has three fundamental demands to insure best value. Replication, replication, replication.
I wonder if there is a gif, like the one we have seen ad nauseum for the Arctic sea ice, for the growth and regrowth of the ice yearly, for the Antarctic?
It seems to me that anytime algorithms are used or mentioned they always increase trends over time no matter what the data is be it, temperatures, sea ice, whatever:. Would rounding errors compounded daily do this over time within an algorithm?
Could the problem simply be how computers are built? Just curious.
I have used the Bootstrap algorithm. It does not estimate quantity but rather uncertainty. A good summary is available (behind a paywall) in a 1998 volume of IEEE Signal Processing Magazine. IEEE summarizes the algorithm as follows: “The bootstrap is an attractive tool for assessing the accuracy of estimators and testing hypothesis for parameters where conventional techniques are not valid, such as in small data-sample situations.”
So when they say they use Bootstrap “to estimate sea ice cover from these data” it does not make sense to me. I does not instil confidence that the article is reliable.
here is an idea,stop using algorithms and satellites to measure things that can be physically measured ,time and time again it is shown that the method does not work,with the added possibility of confirmation bias.