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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Eric, they said themselves, “As noted in earlier entries, persistent high pressure over the central Arctic Ocean led to fairly clear skies for the most of the summer, promoting melt.”
Is there any evidence that persistent high pressure over the central Arctic Ocean is unique, or new in some way? They use the word “extreme” a lot, but I doubt they have significant historical data over the last few millennia to substantiate such a claim.
Eric,
Now that’s serious cherry pickin. If the summer ice is downward trending in the arctic, other ice must be compensating for it right, or the net would be downward????
Don’t pay attention to the man behind the curtain.
Rhys Jaggar,
I concede that volume is a more direct measurement, the belief that volume is independent of extent is a major stretch, especially when you consider larger magnitude changes. Also consider the current AGW science regularly presents this data (arctic only) as evidence of coming doom.
This really was an eye opener for me who has tried to remain skeptical but undecided. I fully expected a very boring series of posts showing the magnitude of the downtrend. In my experience physics has a way of taking your strongest held beliefs and turning them right on their head.
“The summer ice area is the thing to look at, and it is decreasing in the Arctic and more and more ice is one year ice. ”
More correctly, it “was” decreasing, and more and more ice “was” one year ice. The pesky summer of 2008 didn’t go as planned, and thus there is now more 2+ year ice this winter than last winter. When we see 2009 ice increase from 2008, then that will mean there is more 2+ year ice than in the previous couple years.
Just like the cooling trend in place at the moment that gets dismissed as a short-term aberration, I wonder how many years if increasing levels on the summer trough will have to now occur before AGW proponents will move on to the next argument and ignore the trend reversal.
And yes, despite the one data point, I do believe we’ve seen a reversal. The temps in the Arctic have declined now for a few years and it had warmed enough that it makes perfect sense that we would see a lag in the reformation of ice.
Well one thing we can conclude definitely: Global Warming is actually Anthropocentric. It’s our narrow view of time and space which forces us to see shallow pulses in the ziljoen year timespan as monumental pulses in our lifespan. AGW does exist, but thankfully only in our heads.
Jeff ID
I’m also a open-minded skeptic, but that’s why I’m asking whether the measurements have been done.
I have no axe to grind, but my view is that sudden drops in ice extent are more explainable if a large area at the edges thins over several years, thus allowing a big chunk of melting. I have no data to support that, but it seems intuitively reasonable.
Otherwise, you’d expect a uniform increase or decrease in ice extent over multi-decadal cycles.
Wouldn’t you?
Any links you can pass me to which examine this issue?
In some western Alaska villages, heating oil is going up to $11 per gallon this winter.
Why?
When thick ice clogged the slough into Napaskiak, forcing the barge carrying a winter’s worth of heating oil to turn back in October, people panicked.
“The houses were running cold and the businesses were closing their doors,” said Phillip Nicholai, general manager of the village corporation. “It was kind of a disaster.”
…
BLOCKED BARGES
On the day the fuel barge was supposed to arrive in Emmonak, around Oct. 20, Agathluk was flying home to the village from Hooper Bay.
“I could see the Bering coast was frozen from Scammon Bay all the way past the Yukon river,” he said.
The freezeup came earlier than usual …
Yes, I know one winter doth not a trend make, but this sort of story makes it increasingly difficult to lay awake nights worrying about Arctic ice melting.
Graeme Rodaughan (19:55:36) :
“I’m shocked – that poor fellow Pugh paddled all the way to the north pole for nothing…”
Ahem. Fridjof Nansen the Norwegian explorer got 4 degrees further north than Pugh ever did, and that was back in 1893 in a much larger boat, the Fram.
Expedition route here: http://www.fram.museum.no/en/default.asp?page=142
Design of the Fram here: http://en.wikipedia.org/wiki/Fram
Didn’t Pugh turn back at around 80.5 degrees Latitude? Nine and a half degrees of latitude short of target? That’s not even close.
Re: Mark (05:52:35),
Opps, I meant CFC’s. That’s what I get for reading this great site first thing in the morning…
Jeff Id said,
“Eric,
Now that’s serious cherry pickin. If the summer ice is downward trending in the arctic, other ice must be compensating for it right, or the net would be downward????
Don’t pay attention to the man behind the curtain.”
The problem with your graph is that you are adding summer ice in the Arctic to winter ice in the Antarctic in your graphs. As I mentioned the winter ice in the Antarctic can increase as much as it wants without affecting the earth’s albedo.
It seems obvious that this is why scientists look at the two regions separately.
The right way to do this is to offset the Antarctic and Arctic statistics by 6 months if you want to look at winter versus summer trends on one graph by year.
Expressing contempt is not a scientific argument even though it plays well on this web site.
Can you provide data about ice volume versus area? As sea ice thins, it can get pushed out by the mass of land ice, so you end up with ice over a larger area even though there’s less of it.
Eric,
Where does the Antarctic winter ice go in the summer, and how fast?
Eric,
Sorry. That was for Jeff Id.
Jeff Id,
Do you know what the trend for thaw and re-freeze of summer ice is?
Eric
“As I mentioned the winter ice in the Antarctic can increase as much as it wants without affecting the earth’s albedo.”
That must be one of the absurd arguments i’ve ever read. This would be true only if the ice never reached north of the arctic circle and froze/melted instantly upon the appearance/disappearance of the sun. Actually the winter ice reaches maximum about the autumn equniox, when sunlight reaches the South Pole, and the sea ice nowhere extends south of 78 degrees (because there is no sea there).
Actually the argument makes more sense applied to the arctic sea ice – both in winter and summer, since it is at a much higher average latitude and therefore affects albedo much less.
Eric (10:42:39) :
“The problem with your graph is that you are adding summer ice in the Arctic to winter ice in the Antarctic in your graphs. As I mentioned the winter ice in the Antarctic can increase as much as it wants without affecting the earth’s albedo.”
So the Antarctic never gets a summer?
DaveE.
Eric,
I see we aren’t going to agree on this, there are several points in your post I have issues with.
“As I mentioned the winter ice in the Antarctic can increase as much as it wants without affecting the earth’s albedo. ”
The ice still has to melt requiring energy input, during that time the albedo in the area changes. So I don’t believe you can make this statement.
Energy in is energy in and percent reflection from a largely Lambertian diffuser (snow and ice) doesn’t change much with angle. The total energy required to melt the ice from winter to summer with either ice albedo or seawater albedo should be relatively independent of season.
“The right way to do this is ….”
I wanted to look at the overall trend not winter vs summer.
“It seems obvious that this is why scientists look at the two regions separately.”
I can think of another reason that arctic summer ice is the talking point for AGW. I bet most of the people on this blog can think of another reason too.
Whether summer ice is an example of political expedience or it is scientifically valid, the politics of AGW do exist and do pollute the science – see previous Gore post. We cannot simply pretend it doesn’t exist. This means that every claim needs to be scrutinized and assumptions need to be confirmed.
I understand the concept of summer to winter variation being a global warming response but the net change should be negative – and its not! So I would ask, does that mean the summer/winter trend you want to discuss is not a result of global warming?
Eric says:
Well, it really depends on what you are trying to understand. If you are trying to understand the total amount of ice on the planet and whether or not it is static, increasing or decreasing, I would suggest to you that you need to add them together for the same time period.
If you are trying to understand the annual albedo contribution of the ice then you might do a season-based comparison.
How much albedo do the poles contribute anyway, compared to other factors? I suspect a red herring.
Your entire analysis is invalid. You should have read the documentation more closely.
There’s a discontinuity in area data in 1987 because there’s a “hole” in the observed area which is smaller for the SSM/I satellite than for SMMR, hence area data after the switch from one satellite to another are larger — not because ice area was greater, but simply because the area which is “not counted” is smaller:
This is better explained in the documentation given for monthly averages:
Hence there’s an artificial “jump” in sea ice area data of about 0.88 million km^2. Without compensating for that discontinuity, any trend analysis of the data (including this one) has no validity.
If you correct for the discontinuity in the way area is measured, it’s undeniable that global sea ice has trended down over the time span monitored by satellites.
It seems to me that the lag in atmospheric temperature min/max with respect to winter/summer solstices indicates that the oceans’ overall surface temperature is a predominate factor in determining seasonal average air temperatures. Has someone modeled the thermal characteristics of the oceans + solar heat input and would that help explain recent trends in global temperatures?
Oh Drudge Report, how I love thee. Let me count the ways….no, wait…let me count the factual errors in this one news story on My Way News from AP writers Seth Borenstein and Dina Capiello.
http://apnews.myway.com/article/20081214/D952LKP00.html
Phil (22:54:04) :
RE: David Ball (19:11:49):
Anthony: How come we don’t drown via sea level rise each Arctic summer (assuming Antarctica doesn’t freeze as much ice as melts in the Arctic)? Is it because most of the ice that melts in the Arctic is floating ice?
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.
Archimedes approves. The volume of ice is greater (less dense) than the same mass of liquid water.
@chris Wright (04:57:21) :
@Mister Jones (10:19:44) :
I was jesting, I’m well aware of Pughs self promoting folly.
It was the contrast b/w the “notion of an ice free artic that would allow for someone to Kayak all the way there” and “Jeff’s illumination of increasing global sea-ice” that I was driving at – all be it – from an abtuse angle.
For the AGW Warmers – a relatively short time ago – loss of sea ice extent was all the rage as an indicator of Catastrophic Global Warming… The artic was the proverbial Canary in the Global Warming Coal mine that was twittering warnings of the demise of the world.
Why has the argument moved from “ice extent” to “ice mass” – is the extent proxy no longer able to help support AGW – as it is no longer reducing and the artic is not playing ball.
And you accuse sceptics of “cherry picking” data.
I suggest that you look up “Cognitive Dissonance” on Wikipedia. Your little religion of global apocalypse is clouding your minds.
Amen Robert A Cook PE, fear really does sell.
“I can think of another reason that arctic summer ice is the talking point for AGW. I bet most of the people on this blog can think of another reason too. ”
Ohhh, ohhhh, Mr Kotter, Mr Kotter…..
Because the Antarctic ice is not cooperating with their “models.”
sven (23:44:02) :
What’s this? Has the arctic ice been melting?! In december?!
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
Yup. I saw that as well. But no one seems fussed about it. I’m surprised that Anthony hasn’t picked it up….
Jeff Id, a point that may suggest further analysis.
While much is made of summer sea ice melt, it’s irrelevant to the claimed increased greenhouse effect. The best, and arguably only, measure of global warming is winter maximum sea ice extent/area.
This is because the winter maximum excludes any intra-annual effects, which cannot possibly be due to the cumulative effects of greenhouse gas warming over periods greater than a year.
Note that while GHG warming may have intra-annual effects, these effects are of no relevance to climate change/global warming defined as changes over periods greater than a year.
Also note that the GHG effect operates by decreasing cooling. An effect that should be at it’s maximum at night, which in the polar regions is synonomous with winter.
In fact the GHG effect also decreases solar warming at the surface by blocking incoming solar radiation. So an increased GHG effect should manifest in the polar regions in a decrease in winter sea ice extent and a smaller increase in summer sea ice extent relative to the winter maximum extent (ie a smaller annual range in sea ice extent).
I think you will find the exact opposite in all 3 sea ice metrics; winter maximum, summer minimum and annual range, at both poles. Compelling evidence that changes in sea ice extent/area have nothing to do with an increasing GHG effect.