Much importance has been ascribed to tracking the change in Arctic sea ice, but what about the global trend? That doesn’t seem to get much press. However there is some important information that needs to be presented related to the global trend of sea ice as measured by satellite since 1979. The results are surprising. – Anthony
Source: NASA’s Aqua satellite – click for larger image
A guest post by Jeff Id, from The Air Vent
2nd Update 12/24/08 It turns out that an error in documentation at NSIDC is the cause, see this new post for a full explanation.
Update and correction:
To my readers, Anthony Watts received a comment from our friend Tamino on the ice data I used for the area analysis. Unfortunately for me he is right this time. It appears that a correction to the data is required prior to 1987 which will create an approximate negative trend of 0.88 million sq kilometers per 30 years. It is a fairly small trend in the scheme of a 20million sq kilometer signal, but understand this mistake is entirely mine and is unrelated to Anthony Watts excellent blog.
Unfortunately the change makes the Area signal difficult to determine prior to 1988 because the percent fill is unknown. Anthony cannot check every detail of a post which took me days of research and he simply requested if he could copy it here.
The link to my corrections is:
http://noconsensus.wordpress.com/2008/12/16/sea-ice-decreases-despite-the-air-vent/
My apologies.
Jeff Id
I calculated a true global sea ice anomaly in this post using the National Snow Ice Data Center data. What would you say if I told you that over the last 30 years the sea ice area has stayed flat or even trended — Up!!!???
This isn’t a small deal. We have been told, well screamed at really, that CO2 is causing unprecedented rise of temperature on a global scale. We hear constantly that the ice is melting and the result will be dramatic flooding of the earth; movies have even been made. Those of us who pay attention to the scientists have heard that the most significant warming will be at the poles (according to the computer models). We also hear that the Antarctic has added ice during the same time the Arctic lost sea ice. This is explained in that the Antarctic ice increase is a local situation and the Arctic ice loss is a result of global warming. A unique form of cherry picking but should be treated with an open mind.
If you’ve been paying attention, you have heard that the net ice level is going down. The Antarctic gain cannot compensate for the Arctic loss. Well, I set out to see how bad the situation is.
First, anthropogenic global warming scientists use two measures, extent and area.
Extent looks at all the square Kilometers (Km^2) with more than 15% ice in them and adds them up.
Area looks at all the square Kilometers (Km^2) with more than 15% ice in them and adds them up but multiplies the Km^2 by the amount of ice in the square kilometer. i.e -(if you have 1 Km^2 of sea filled 15%, ice- extent counts it as 1Km^2 while area counts it as 15% of 1Km^2 or 0.15Km^2)
This post deals with the amount of sea ice so I used Area. In the future Iwill do it with extent. The NSIDC uses two algorithms for calculation of sea ice, nasateam and bootstrap. We will look at both here.
Without modification the NSIDC data for bootstrap runs from 1978-Dec. 2006 and the nasateam runs from 1978-Dec 2007, these near 30 year trends comply close enough with current science which states (conveniently) that climate requires a 30 year trend to see the result.
This is a graph of the global sea ice area from the nasateam algorithm.
The red line is the slope of the global sea ice data from nasateam in its raw format. The slope is negative by only 6803 Km^2/year and the mean is 18,290,000 km^2.
We should look at sea ice anomaly to be the most accurate for trend. To calculate sea ice anomaly I took the average shape of the annual signal and subtracted it from the curve above.
The average ice variation globally looks like this on an annual basis.
I subtracted this curve above to get the sea ice anomaly.
The downward slope of this graph is more extreme but the scale is highly magnified. The net downslope in 30 years of global warming is – 10173Km^2/year. Over 29 years of data this means that we have lost 302025 Km^2 of ice. This is a 1.65 percent drop in global ice level in 30 years. Remember though that this data ended on an extraordinary high melt year of 2007, the ice level can be seen recovering in dec 07 leading into 2008. This shows as a slight change in slope of the very tip of the first graph (a subtle, difficult to see effect).
Well NSIDC recommends using the Bootstrap algorithm for research instead of Nasateam because of certain errors which have been corrected for.
The bootstrap algorithm plot for global data looks like this.
The red line is slope again, and this time it is positive, indicating an increase in ice level from 1978-Dec 2006. The slope of the red line is plus 6341 km^2 per year indicating that the earth in 28 years has added 177,000 sq kilometers of ice with a mean ice level of 20.42 million Km^2.
The anomaly is better for calculating trends because it cleans up the end points making the slope insensitive to the start and stop point of the annual cycle.
The up trend for the anomaly in sea ice from 1978 to end 2006 is 804Km^2 per year. Which in our timeframe the preferred bootstrap algorithm says the earth ADDED 22,000 Km^2 of ice area!!
Here are the anomalies rescaled to actual by adding the mean of the original data back in.
Obviously people cannot make the claim that sea ice is being lost. It isn’t. The data shows that our trend is basically flat during this time of unprecedented temperatures. It’s clear that there has been no significant change in sea ice area.
This is almost enough to make me turn in my Skeptic union card, but increased CO2 warming the earth makes some sense to me, the magnitude is in question. The fact that polar sea ice not melting is not an insignificant point. It is also important to realize that the changes are too small to fit with IPCC statements about the trend. Unlike trees, ice does make a good thermometer. I can’t say this strongly enough— This is a strong indication of substantial errors in the computer models and temperature data which needs to be addressed before we throw what’s left of our global economy to the wind. How would Earth’s total sea ice ignore such substantial warming? It’s a good question which deserves an answer.
I will update this when new data becomes available and will also attempt to demonstrate that the net slopes we see are within the margin of error for the measurement in a future post. In the meantime, lets let the world know the truth. We aren’t going to drown any time soon!
————————
I had a request for description of the difference between the bootstrap and nasateam algorithms. It is a bit complex but it seems well documented on the NSIDC here are a few links and descriptions from that site. From FAQ section.
2. What is the difference between the NASA Team algorithm and the Bootstrap algorithm?
For general analyses or creation of simple images, either algorithm will suffice. The Bootstrap sea ice concentration data set is believed to be more useful for modeling and process studies in the polar regions because it is generally free of residual errors that could not be removed by conventional techniques. A temporally more consistent time series of sea ice concentrations is provided, offering improved accuracy over the ice concentration maps created from the original Bootstrap algorithm.
More interesting to me was the table provided which shows the strenghts and weaknesses of each process. The original table is at the link above.
For more details and complete descriptions NSIDC provides two links Bootstrap and Nasateam
HERE is a link to the R code to make the above graphs.
Data sources:
ftp://sidads.colorado.edu/pub/DATASETS/seaice/polar-stereo/
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An area of ice the size of the United States melts and re-freezes each year. This is an important article. Thank you Jeff
The raw theory that increasing CO2 will “show up” at the poles makes sense: The AGW extremists know that at the poles the air is both extremely cold AND extremely dry (on average) so CO2 (at the same percentage as in warmer, more humid areas (ie, the rest of the planet!) makes up a significantly greater amount of the total greenhouse gasses present.
If CO2 increases, then (reasonably) there will be a significantly greater percentage increase in greenhouse gasses at the poles than in the rest of the plant.
Therefore, since (in their minds) CO2 is the great evil, and since there are no other GHG than Co2, the poles MUST melt first. So, every thought in their minds since Hansen’s 1988 presentation to Congress has focused on the “proving” that the poles will melt. (And then kill us all.)
[Notice how the common Mercator projection in every classroom that exaggerates Greenland’s area helps this fear: When Greenland is projected as nearly twice the size as Australia, and when Greenland is displayed as about the same size as Brazil or Africa, then (when) that “huge area” melts, obviously the earth “must get” catastrophically flooded … And the politicians play on this fear – as Gore so recently did.
——
Notice too that even ONE YEAR of “normal ice re-freezing throws out every real piece of the scare tactics: The ice that must melt in say 2010 is what was left over from 2009 into 2010. What was melted in summer 2007 (and then re-froze in winter 2008-2009) doesn’t matter at the edges of the ice pack.
True a long-term trend would matter – But from these graphs there is no long-term trend of costantly melting ice.
—
Yet the politicans, and their budget-linked members of the “science” community don’t care.
Fear sells.
Truth shows previous lies as the lies that they are.
So, even with the big melt in 2007, we still see an average increase in sea ice anomaly trend with bootstrap. In that case, if you ignore the 2007 data (just for the fun of it) I bet we would see a much greater slope upwards in the 30-year trend. 2007 looks like an anomalous year, which may be influencing the statistics too much and masking a more realistic climatic trend. Just like the 1998 El Nino temperature-anomaly spike doesn’t seem to help the calculation of its long term trend, but only to increase its statistical fluctuations.
This compares well with the global sea ice graph from
bah Cryosphere
I’m shocked – that poor fellow Pugh paddled all the way to the north pole for nothing…
Is it possible to get this work into a “Peer Reviewed” journal?
Excellent work Jeff.
It also begs the question – of why hasn’t NSIDC noticed this and published these results?
I’m puzzled, why the 15% rule for the area? Why not adding everything?
In computing extent I understand the need for a cut-off like this, but even then an indication should be added with the size of the regions with let’s say 15% +- errors from instrument sensitivity. I’d like to have an idea of the biases that come from simple truncation.
I hope this analysis is right…
An interesting check to my results is at this link.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg
The university of Illinois is using a slightly different dataset. I wrote for the data but haven’t received a reply. You can see from the graph that the shape of the curves I calculated is accurate. UIUC data has a ‘slightly’ stronger negative slope for some reason.
A really inconvenient truth — it seems that total polar sea ice is essentially stable, notwithstanding Mr. Gore’s panic attack prediction.
The truth is full of (strike(good news) bad news.
I see a 3-4 year downward trend (2003-2007) also it appears we are starting into an upward trend. the agw crowd will cherry pick this as “proof” of ice loss. I see the beginnings of a cold trend as the Antarctic remains frozen and the arctic begins to freeze up more. less food can grow in the cold. longer winters. more clouds.
what would be interesting would be to subtract the two variations ( bottom two grafts) and see the error ( noise ). because that is what they (agw promoters use) to twist the data around.
Good job Jeff
RE: David Ball (19:11:49):
REPLY: Yes, try the ice cubes in a glass filled to nearly the top with water experiment. They float, they melt, but the glass does not overflow.
Greenland ice is an entirely different issue, since it is land bound. – Anthony
Yes.
Jeff Id,
May I ask some questions concerning the difference of the two methods.
The nasateam data extend closer to present day than the bootstrap data. Does nasateam use a running mean taken over previous data, while bootstrap uses a mean including forward data as well?
When looking at the two anomaly curves, they show a similar peak structure. But subtracting the two curves will not generate white noise?
Maybe, when you put in a certain time shift between the two curves?
I love how you say cherry prick, you take only sat photos, completely ignore all other data such actual physical investigations of the caps.
Studies which have physicly found that the Perma-ice has lower denisity and is now honeycombed with airpockets.
If you can provide me with data that shows that hundred of thousands of years old ice which used to be known as completely solid but which has now lost a good majority of its internal volume is normal.. or the data is all made up.
I might actually believe our planet isnt as screwed up as they say.
What’s this? Has the arctic ice been melting?! In december?!
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
The northern hemisphere has more people, more CO2 emissions, and more water to moderate the effects of AGW. The Antarctic and the southern hemisphere was predicted to lag behind the northern hemisphere in its response to AGW:
http://www.realclimate.org/index.php/archives/2008/02/antarctica-is-cold/langswitch_lang/sw#more-529
The shape of the 30 year average sea ice area is also very interesting. Assuming that the Day of Year axis represents a normal western calender, the areal extent of sea ice seems to fall to a minimum during the Antarctic summer, with a much smaller dip during the Arctic summer. That suggests that there is a lot more sea ice around the perimeter of Antarctica than in the Arctic region, contrary to my expectations.
Area does not equal mass. Very deceptive data mining.
Lamont: SST for the Southern Ocean stopped its rise more than 20 years ago and has been on a sharp decline for more than 10 years.
http://i35.tinypic.com/s3djds.jpg
With respect to your realclimate link, they searched and found a few reports that discussed very specific climate models of the Antarctic and the Southern Ocean to illustrate that “A cold Antarctica and Southern Ocean do not contradict our models of global warming. For a long time the models have predicted just that.”
But what do other models say? Look at the two graphics of GISS equilibrium runs used by realclimate in another discussion, the first two figures in the following.
http://www.realclimate.org/index.php/archives/2007/12/tropical-troposphere-trends
There is NO cooling in the lower troposphere of the Antarctic in either illustration. While the high latitudes in the Southern Hemisphere do not warm as greatly as they do in the North, they still show warming,
Climate models contradict one another, so some will be consistent with reality while others will not. What value do they have then?
@phoynix
“Studies which have physicly found that the Perma-ice has lower denisity and is now honeycombed with airpockets.”
Can you give us a reference to any of these?
“If you can provide me with data that shows that hundred of thousands of years old ice which used to be known as completely solid but which has now lost a good majority of its internal volume is normal.. or the data is all made up.”
Not sure what this means, but if you are looking for data on ice mass then I know that there are gravity-based estimates of ice mass, which would automatically correct for cavities in the ice.
“I might actually believe our planet isnt as screwed up as they say…”
I don’t think ANY planet can be a screwed up as ‘they’ say…..
Lamont: You wrote, “The northern hemisphere has more people, more CO2 emissions, and more water to moderate the effects of AGW.”
First, CO2 is a “well-mixed greenhouse gas”, so that part of your statement has little substance. Second, oceans cover approximately 60% of the Northern Hemisphere, and for the Southern, they cover about 80%, so that part of your statement is wrong.