We have news from the National Snow and Ice Data Center (NSIDC). They say: The melt is over. And we’ve added 9.4% ice coverage from this time last year. Though it appears NSIDC is attempting to downplay this in their web page announcement today, one can safely say that despite irrational predictions seen earlier this year, we didn’t reach an “ice free north pole” nor a new record low for sea ice extent.
Here is the current sea ice extent graph from NSIDC as of today, notice the upturn, which has been adding ice now for 5 days:
Here is what they have to say about it:
The Arctic sea ice cover appears to have reached its minimum extent for the year, the second-lowest extent recorded since the dawn of the satellite era. While above the record minimum set on September 16, 2007, this year further reinforces the strong negative trend in summertime ice extent observed over the past thirty years. With the minimum behind us, we will continue to analyze ice conditions as we head into the crucial period of the ice growth season during the months to come.
Despite overall cooler summer temperatures, the 2008 minimum extent is only 390,000 square kilometers (150,000 square miles), or 9.4%, more than the record-setting 2007 minimum. The 2008 minimum extent is 15.0% less than the next-lowest minimum extent set in 2005 and 33.1% less than the average minimum extent from 1979 to 2000.
Overlay of 2007 and 2008 at September minimum
The spatial pattern of the 2008 minimum extent was different than that of 2007. This year did not have the substantial ice loss in the central Arctic, north of the Chukchi and East Siberian Seas. However, 2008 showed greater loss in the Beaufort, Laptev, and Greenland Seas.
Unlike last year, this year saw the opening of the Northern Sea Route, the passage through the Arctic Ocean along the coast of Siberia. However, while the shallow Amundsen’s Northwest Passage opened in both years, the deeper Parry’s Channel of the Northwest Passage did not quite open in 2008.
A word of caution on calling the minimum
Determining with certainty when the minimum has occurred is difficult until the melt season has decisively ended. For example, in 2005, the time series began to level out in early September, prompting speculation that we had reached the minimum. However, the sea ice contracted later in the season, again reducing sea ice extent and causing a further drop in the absolute minimum.
We mention this now because the natural variability of the climate system has frequently been known to trick human efforts at forecasting the future. It is still possible that ice extent could fall again, slightly, because of either further melting or a contraction in the area of the pack due to the motion of the ice. However, we have now seen five days of gains in extent. Because of the variability of sea ice at this time of year, the National Snow and Ice Data Center determines the minimum using a five-day running mean value.
Ongoing analysis continues
We will continue to post analysis of sea ice conditions throughout the year, with frequency determined by sea ice conditions. Near-real-time images at upper right will continue to be updated every day.
In addition, NSIDC will issue a formal press release at the beginning of October with full analysis of the possible causes behind this year’s low ice conditions, particularly interesting aspects of the melt season, the set-up going into the important winter growth season ahead, and graphics comparing this year to the long-term record. At that time, we will also know what the monthly average September sea ice extent was in 2008—the measure scientists most often rely on for accurate analysis and comparison over the long-term.
It will be interesting to see what they offer in the October press release. Plus we’ll be watching how much ice we add this winter, and what next year’s melt season will look like. Hopefully we won’t have a new crop of idiots like Lewis Gordon Pugh trying to reach the “ice free north pole” next year.
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Oops, typo in list line. Percent is wrong, ampersand is right.
The table is formatted with <code> commands and with spaces replaced with . (And will this sentence format right?)
Anne: “1) Your tone in your wording was highly confrontational, boarding on insulting and quite unnecessary… Treat people as you wish them to treat you.”
Thanks for this ruling, Anne. I have seen too many blogs go sour when posters begin laying into each other. Mind you, I don’t think Mary is at particular fault in this regard, and it’s a moot point whether her postings are any more confrontational than others. But you are the moderator, so it’s your call. And the golden rule is a valuable guide to the way posters should behave.
That said, your ruling raises a more general issue about poster behaviour, which I will illustrate with some examples below.
“It’s propaganda, political, partisan, partial…the audacity, the arrogance, the narcissism…deception…hysteria…slippery, double-dealing group…idiotic vacuous pronouncements…have lost their minds…corrupt…about as impartial as an alcoholic bartender…biggest global fraud…lunatic cries…discussing their next scam…”
If said to other posters, these comments would probably, and rightly, be snipped. But they are comments about third parties, and there appears to be a more relaxed standard for these sorts of comments.
My question is: are third parties fair game for comment, or are there limits to what can be said about them?
Reply: While Anthony has the final say on this, my take is that ‘Them thar be fightin’ words’ have no place here. The same standards should apply to all parties, present or otherwise, with the following exceptions as noted below –
There should be some leeway for the ocissional gaff from an otherwise good party. Habitual offenders get warned much faster.
There is also a difference between an attack on an opinion held and an attack on the person holding the opinion. The former gets more leeway and latter is never acceptable.
Finally, the US rules for libel and slander apply as well, public figures, because they chose to be public, they also choose to suffer the slings and arrows of outrageous fortune. So it might be OK to call Hansen a liar or a kook in regard to a public action he has taken, but it would not be OK to call you a kook for agreeing with him.
The debate over AGW is hotly contested and should be decided not by a battle of strength of personalities, but on the merits of the data. If we remember to keep principles over personalities, we will get along just fine while we debate the issue.
I hope this helps. – Anne
To respond to some points above:
Oops, I’m unfamiliar with the formatting on this site. My post is missing a bunch of cites from upthread. Hopefully regulars can make sense of it. Apologies.
If you do Individuals control charts with the above data, control limits for each column come out as:
May ice 12.5 to 14.4
Sep Ice 5.2 to 8.1
Melt 5.0 to 8.5
Freeze 4.7 to 8.7
For May: flags are raised for 2004-2006 data as being outside two standard deviations from the mean.
For Sep 2002-2006 data demonstrates a low trend and 2007-2008 are outside of the control limits.
For Melt: 2007 and 2008 are outside the upper control limit.
For Freeze: 2007 is outside the upper control limit.
So, the May / Sep data show a statistical downward trend since approximately 2000. You could draw a decent regression line with a negative slope (-0.037/year, R2(adj=51.4%) back to the start of the data. Melt rates were within statistical control (varying within their apparent natural range) until 2007. Freeze data has also been within statistical control, with the exception of 2007, which demonstrated a higher than expected value.
The amount of ice in May doesn’t show a correlation with Sep, Melt, or Freeze. Sep shows a negative correlation with Melt and Freeze. (Lower Sep higher Melt – makes sense. But also lower Sep higher Freeze.) Melt and Freeze have a positive correlation. (higher Melts, higher Freezes)
Mike86
What’s the reasoning behind selecting May stats? Maxima usually occur in March. There is a fair bit of variability during the melt/growth seasons, particularly the melt, so I imagine you could find idiosyncratic trends depending on which month you trended, and playing around with different periods.
I think using the whole series is simplest and sticking with maxima and minima. WMO puts a statistically significant climate period at 30 years (though some climate scientists reckon 20 and even 15 years is can be a valid period). I assume NSIDC ran a trend for the whole satellite period, showing an increased melt rate 1979 – 2007 to 1979 – 2008. In any case, I was replying to the intuitive notion that a less of a melt in the final year (2008) should produce a decreased trend. You clearly know more about statistical analysis than I do. I bet you could come up with a clearer, more succinct explanation of why trends don’t jibe with intuition WRT this specific example. I’d appreciate it if you would. I don’t think my attempt was clear enough.
Previous post by Ric said this was as far back as the NSIDC ice data went, therefore it’s what I used for the analysis. 25-30 points isn’t bad for establishing control limits with an Individual’s control chart.
The control limits just give an idea of the possible data range based on the observed variability. This assumes the data is normal, which this set is. You can watch how the data moves over time to determine if the data are not behaving randomly (eg there’s a trend or something’s changed). There are some basic tests / checks for this that are easily Googled.
Based on this data, the historic melt rate doesn’t really have a trend. It randomly fluctuates around a mean. The 2007 and 2008 melt data are outside of the control limts, meaning they appear to be outside the anticipated data range. With two years in a row reporting outside of the upper control limit, the conclusion would be that something controling this parameter changed.
Don’t ask me what changed, but, based on the above data alone, the effect happended to the melt rate in 2007.
Re. Ric Werme (20:04:05) :
Pamela Gray (18:58:29) :
The ice recovery this past winter was huge. A record setter since satellite records began.
“It didn’t even make it back to the ‘79-2000 average, not much of a record” setter.
“My spreadsheet says the average freeze was 6.68 M mi^2 and that the 07/08 freeze was 8.89. What is your data? (Caveat – my data comes from May and Sep data, I don’t know where values for Annual max and min are. Pointer welcome.)”
2007 ice area minimum 2.92 Mm^2
2008 ice area maximum 13.9 Mm^2 (average max. ~14.3 Mm^2)
2008 ice area minimum 3.004 Mm^2 (average min. ~5.0 Mm^2)
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.365.jpg
“9.4% isn’t “a couple” in my book. What is your data?”
3.004/2.92 = 1.027
For a graphical representation see here:
http://arctic.atmos.uiuc.edu/cryosphere/ice.area.at.minimum.new.png
Anne: “The same standards should apply to all parties, present or otherwise, with the following exceptions as noted below…”
Thanks for taking the time to offer your views, Anne. I think you have presented some valuable guidelines, especially the distinction between attacking views and attacking persons. That said, may I seek further clarification? Below is a list of statements that I think summarise this situation and your views.
1. Watts Up With That subscribes to a ‘civility principle’.
2. Your comments relate to your role as moderator on this forum, but are not necessarily forum policy.
3. Attack the opinion, not the person.
4. Poster-to-poster personal insults are unacceptable.
5. Occasional gaffes are forgiveable.
6. Insults about the publicly expressed views of third-party public figures are OK.
If this list fairly summarises your views, I’m fine with that. However, I would like to clarify the status of another class of comments: those that are directed towards third-party categories/groups of people rather than specific individuals.
For example, if I were to claim that ‘AGW sceptics are nut-jobs’, that would not be a direct insult against any particular poster, yet some individuals might take umbrage because they consider themselves to be part of the category of AGW sceptics.
What would your ruling be on this class of comments? Is it OK to make insulting comments about categories/groups of persons, or do you think they should also be subject to the civility principle?
Reply: I think that each moderator should rely on their own judgment in this sort of situation upon receipt of a complaint from a member of the ‘offended’ group, taking into account the context of the comment within the discussion, as well as the past behavior of the poster and the complainer. Remember, this is Anthony’s blog and he gets the final say. – Anne
[FURTHER REPLY – Aye, aye! Arrr. ~ E]
barry (09:31:46) :
No good reason, just several bad ones. Mainly I saw a graph started in June, so I picked May. I didn’t even compare adjacent months. Lazy and late. I’ll take another
look tonight, I’m still at work (EDT, pizza night, so I’ve had dinner).
Was that directed toward me? I’m a software engineer, not a statistician! I was thinking about figuring out how to do a linear regression in my spreadsheet, and that requires little more than knowing how to spell it!
Getting matlib and scipy running is high on my list of things I don’t have time to do. that will let me make pretty graphs and pretty graphs bring an air of authority. Don’t they?
Oh, ice area. We were talking about ice extent. Maybe I’ll look at area tonight too.
Hi Ric.
I was talking to Mike86. I hadn’t read to the bottom of the thread when I first posted, and then replied to posts that came after mine. I’ve seen your post now – appreciate the stats. Would you mind posting the link to them?
I’m no statistician either. I just know the right buttons to press in Excel. I learned some basic stuff to discuss global temperature trends elsewhere.
I ran a simple regression for September minima from 1979 – 2007, and then another from 1979 – 2008. Sure enough, the trend at peak melt seems to have ‘accelerated’ when you include this year’s data point. The opposite is true using the May figures.
I suppose another way of doing it would be to take the Jan – Dec average rather than picking months, but the minima seems like the most vital because of potential tipping points.
[…] Anthony Watts has the story: Arctic Sea Ice Melt Season Officially Over; ice up over 9% from last year […]
I guess saying “nutjobs” is ok since it wasn’t snipped.
Reply: It was a vague reference with no defined target at a specific person or entity. – Anne
There’s always the option of holding oneself to a higher standard than the bottom line.
On the forum I’ve been managing I spell out some posting guidelines and a few hard rules. Some contributors are always asking how low they are permitted to go and find inventive ways of pillorying each other while staying within the letter of the ‘law’. I’m a fair-minded person, so rather than clamp down on artful language that perpetuates acrimony and beggars a progressive discussion without precisely breaking the rules, I’ve decided to hand the forum over to somebody else. I figure if I want to preside over that kind of squabble I’ll have kids or become Speaker of the House in Australian Parliament.
I don’t bother long with blogs and such that have the same sort of action. I want to learn stuff and have people genuinely test my ideas, but the pace is always slow on that where broadsides accompany reason.
“Ignorance can be cured by curiosity. I don’t know if there is a cure for a lack of curiosity.”
OK Brendan it’s a case by case basis… Thanks Anne
Reply: Pretty much. As I suspect that the Mayan-calendar subscribing members of the Internet don’t frequent WUWT, the comment stands. – Anne
Ric Werme (16:39:02) :
Oh, ice area. We were talking about ice extent. Maybe I’ll look at area tonight too.
How can you talk about ‘melt’ and ‘freeze’ when you’re referring to ‘extent’, you’re observing ‘melting and dispersion’ and ‘freezing and compaction’? Most of this year’s increase in extent over last year is due to dispersion.
Found monthly data sets for the satellite series at NSIDC (Arctic sea ice), with figures for area and extent side by side.
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/
Maximum (March) is here.
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Mar/N_03_area.txt
Minimum is here.
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/N_09_area.txt
Listed under ‘area’ (top file each month listing). September 2008 hasn’t been included yet. As I’m a rube with the formatting here, I’ll leave it to others to post tables. Hope this is useful.
I ran a linear regression for maxima over the series and the declining trend has decelerated as a result of maximum last March, emphasising in a different way the remarkable melt season this year.
Ric Werme,
When you’re plugging all of this into your spreadsheet, could you do a sorted list of ‘delta ice’ (area or extent)? From the year-over-year growth standpoint?
Because there aren’t a lot of increases in the most recent years – the current increase may be particularly poignant.
Phil. (13:25:38) :
Sorry, it took me a bit longer to stick data together than it might have. Barry reported the same data source as I found, and indeed I should’ve used March data for starting extent. Their September file doesn’t have September 2008 data yet, so I used yours. Their 9/2007 ice area data point is only 2.77, whereas yours is 2.92, all M Km^2, Millions of square Km, or Tm^2, trillions of square meters.
3.00 / 2.77 = 1.083, or 8.3% more ice area.
Here’s a table of Year, Melt and Freeze areas, and March and September areas. Hope I get the magic HTML right.
Year Melt Freeze Mar Sep
1979 8.60 8.39 13.13 4.53
1980 8.09 7.79 12.92 4.83
1981 8.24 8.61 12.62 4.38
1982 8.61 8.46 12.99 4.38
1983 8.20 7.84 12.84 4.64
1984 8.43 8.61 12.48 4.05
1985 8.49 8.48 12.66 4.17
1986 7.99 8.09 12.65 4.66
1987 7.15 8.24 12.75 5.60
1988 8.53 7.83 13.84 5.31
1989 8.33 8.63 13.14 4.81
1990 8.94 8.85 13.44 4.50
1991 8.89 8.95 13.35 4.46
1992 8.04 8.34 13.41 5.37
1993 9.19 8.95 13.71 4.52
1994 8.39 8.19 13.47 5.08
1995 8.89 8.45 13.27 4.38
1996 7.25 7.66 12.83 5.58
1997 8.40 8.66 13.24 4.84
1998 9.26 9.23 13.50 4.24
1999 9.25 8.88 13.47 4.22
2000 8.79 9.26 13.10 4.31
2001 9.02 8.81 13.57 4.55
2002 9.38 9.38 13.36 3.98
2003 9.35 8.92 13.36 4.01
2004 8.58 8.32 12.93 4.35
2005 8.64 8.41 12.67 4.03
2006 8.48 8.53 12.44 3.96
2007 9.72 10.39 12.49 2.77
2008 10.16 13.16 3.00
Here’s the extent data much like the area data. I didn’t see the “waiting for moderation” message, so it may be spam. It may also be misformatted, in which case this will be also.
Year Melt Freeze Mar Sep
1979 9.24 8.93 16.44 7.20
1980 8.28 7.76 16.13 7.85
1981 8.36 8.90 15.61 7.25
1982 8.70 8.65 16.15 7.45
1983 8.58 8.10 16.10 7.52
1984 8.45 8.89 15.62 7.17
1985 9.13 9.15 16.06 6.93
1986 8.54 8.41 16.08 7.54
1987 8.47 8.65 15.95 7.48
1988 8.64 8.03 16.13 7.49
1989 8.48 8.84 15.52 7.04
1990 9.64 9.26 15.88 6.24
1991 8.95 8.92 15.50 6.55
1992 7.92 8.33 15.47 7.55
1993 9.38 9.08 15.88 6.50
1994 8.40 8.14 15.58 7.18
1995 9.19 8.99 15.32 6.13
1996 7.24 7.70 15.12 7.88
1997 8.84 8.92 15.58 6.74
1998 9.10 8.84 15.66 6.56
1999 9.16 9.03 15.40 6.24
2000 8.95 9.29 15.27 6.32
2001 8.86 8.69 15.61 6.75
2002 9.48 9.53 15.44 5.96
2003 9.34 8.90 15.49 6.15
2004 9.00 8.69 15.05 6.05
2005 9.17 8.86 14.74 5.57
2006 8.54 8.78 14.43 5.89
2007 10.39 10.93 14.67 4.28
2008 10.69 15.21 4.52
Alan S. Blue (10:22:14) :
When you’re plugging all of this into your spreadsheet, could you do a sorted list of ‘delta ice’ (area or extent)? From the year-over-year growth standpoint?
Because there aren’t a lot of increases in the most recent years – the current increase may be particularly poignant.
Poignant?
Here’s the extent table sorted by extent increase during the winter. I’m not sure if it’s very useful, though it does show the relationship between start and end levels. The years with the biggest freezes are the ones with the least ice to start with and the most area available to freeze. I added a column – the amount of ice in March after the winter. That way you don’t have to searching for that amount.
Year Melt Freeze Mar Sep Next
1996 7.24 7.70 15.12 7.88 15.58
1980 8.28 7.76 16.13 7.85 15.61
1988 8.64 8.03 16.13 7.49 15.52
1983 8.58 8.10 16.10 7.52 15.62
1994 8.40 8.14 15.58 7.18 15.32
1992 7.92 8.33 15.47 7.55 15.88
1986 8.54 8.41 16.08 7.54 15.95
1982 8.70 8.65 16.15 7.45 16.10
1987 8.47 8.65 15.95 7.48 16.13
2001 8.86 8.69 15.61 6.75 15.44
2004 9.00 8.69 15.05 6.05 14.74
2006 8.54 8.78 14.43 5.89 14.67
1989 8.48 8.84 15.52 7.04 15.88
1998 9.10 8.84 15.66 6.56 15.40
2005 9.17 8.86 14.74 5.57 14.43
1984 8.45 8.89 15.62 7.17 16.06
1981 8.36 8.90 15.61 7.25 16.15
2003 9.34 8.90 15.49 6.15 15.05
1991 8.95 8.92 15.50 6.55 15.47
1997 8.84 8.92 15.58 6.74 15.66
1979 9.24 8.93 16.44 7.20 16.13
1995 9.19 8.99 15.32 6.13 15.12
1999 9.16 9.03 15.40 6.24 15.27
1993 9.38 9.08 15.88 6.50 15.58
1985 9.13 9.15 16.06 6.93 16.08
1990 9.64 9.26 15.88 6.24 15.50
2000 8.95 9.29 15.27 6.32 15.61
2002 9.48 9.53 15.44 5.96 15.49
2007 10.39 10.93 14.67 4.28 15.21
2008 10.69 15.21 4.52
Nice work, Ric.
Someone said a few posts ago that a trend wasn’t discernible. I still don’t understand why. The minima extent swing year to year is within 500 000 sq kms, and the linear trend from start to finish is over 2 mil sq kms, four times the variability. If 30 years is long enough to establish a climate trend, then it seems there is one.
Including this year, it’s closer to -2.5 mil sq kms linear trend, five times the variability of minimum year to year.
If people are worried about the ice cap melting, wouldn’t there be a better perspective if the area graphics didn’t suppress the zero?
Or are we interested in “measurement noise”?
In the last hundred years there were two thirty year trends of temperatures rising. They both stopped. http://www.cru.uea.ac.uk/cru/info/warming/