10/31 NEWS: See updated graphs here
UPDATED: 10/22/08 The new images below are even closer
Watching arctic sea ice rebound this year has been exciting, more so since a few predictions and expeditions predicated on a record low sea ice this past summer failed miserably. I’ve spent a lot of time this month looking at the graph of sea ice extent from the IARC-JAXA website, which plots satellite derived sea-ice extent. However, there is another website that also plots the same satellite derived data, the Nansen Environmental and Remote Sensing Center of Bergen Norway, and they have an added bonus: a standard deviation shaded area. For those that don’t know what standard deviation is, here is a brief explanation from Wiki
…standard deviation remains the most common measure of statistical dispersion, measuring how widely spread the values in a data set are. If many data points are close to the mean, then the standard deviation is small; if many data points are far from the mean, then the standard deviation is large. If all data values are equal, then the standard deviation is zero.
In a nutshell, you could say that any data point that falls within the standard deviation area would be considered “within normal variances” for the data set. That said, current sea ice extent and area data endpoints (red line) are both approaching the edge of the standard deviation (gray shading) for both data sets. Here is sea ice area:
Click for a larger image
And here is sea ice extent:
Click for a larger image
Extent has a bit further to go than area, and of course it is possible that the slope will flatten and it may not reach the SD gray area. It’s also possible it may continue on the current trend line. Only nature knows for certain. A complete presentation from Nansen is on this page which is well worth bookmarking.
What I find particularly interesting is the graph comparing the 2008, 2007, and 2006 sea ice extent. It appears 2008 extent has already bested 2006 extent:
with a hat tip to commenter Patrick Henry
My two solacing pleasures during this election cycle
Me, too.
Hey, we have moose now in Wallowa County. Are polar bears far behind?
My bad. That map I reference:
http://explorenorth.com/library/maps/franzjosefland1906.htm
marks that white area as unerforschtes gebiet which, roughly translates into unknown territory. tsk tsk
RealClimate just posted up a study that says tropical temperatures are within the model’s predictions since they are still within 2 standard deviations.
Someone needs to post this at RealClimate because 2 standard deviations is ridiculous. Using this measure, no warming at all in the tropics (basically what the actual observations are) is still consistent with the models. LOL
If sea ice is within 1 standard deviation, they should be told to quit talking about a loss of sea ice since their own measure says there is no change.
Gardy LaRoche (15:42:04) :
Here’s the definition that the NSIDC uses:
PeteM : Chris Booker’s work is invariably well researched, but if you wish to challenge his journalism go to eureferendum.com where the background to his work is usualy published and open to discussion before he goes to press. I hope you will come up with something a bit more relevant than your bland posting on this otherwise erudite forum.
In a nutshell, you could say that any data point that falls within the standard deviation area would be considered “within normal variances” for the data set.
Yes, but usually anything within two standard deviations would be considered within the normal range.
From the Arctic ROOS website:
Ice Area is defined as the area covered by ice, excluding regions with 15% or lower ice concentration. Ice extent is defined as the area with a 15% or higher ice concentration.
See also their plot of extent and area from 1978 to 2007.
http://arctic-roos.org/observations/satellite-data/sea-ice/total-icearea-from-1978-2007
Compare that to the more alarming graph in the recent Dr. Meier post (16-10-2008).
Cathy: “Median” is a bit more obscure than “normal”
“median” has a precise meaning, “normal” (in this context) doesn’t.
PeteM,
You say: Green issues won’t go away no matter how much you wish we’re not living on an overcrowded planet and are currently changing the composition of the atmosphere.
The DT has done a great service by raising awareness of important issues.
I do agree that the planet is overcrowded. Like you I don’t have children. Like you I find the evironment a very important issue. Like you I mostly use my bicycle for transport and I don’t have a car. Like you I wear a warm sweater when I’m cold instead of turning the thermostat higher. Like you I can’t be blamed for hypocrisy
But unlike you I am interested in science and want to know the truth with all its inevitable nuances, for only that will bring humankind further.
There may be questions as to the validity of the historical average. Melling and Riedel (GRL 2005) did a sonar survey of the ice in the Beaufort Sea from 1991 to 2003. They no signifigant trend in area or thickness. They also state that the Beaufort Sea is “ice free for four months except for low density intrusions”. Cryroshere Today anomaly graph shows a norm of 25 to 30 percent for August.
I should add that their explanation of area versus extent is a bit confusing…
… so I found a previous WUWT comment:
“extent is the area of ocean containing 15% ice, ‘area’ is the calculated area of the ice itself”
@Pet Rock
Technically, of course, ‘median’ is more precise than ‘normal’.
I may have used ‘obscure’ awkwardly, but I meant that in switching terms at this interesting time of ice recovery they seemed to be trying to obscure the fact of the ice cap’s return to ‘normalcy’ .
John D
Search this site for “Alaska glaciers”, there’s an article about the growing glaciers in Alaska.
There were a pile of articles about glaciers in the Cascades and the Mount Rainier retreating… a couple years ago. But somewhat lacking on followthrough.
Tom in ice free Florida (15:11:40) :
“Now if we could just get the data to go back and start at 1907 it would be even more meaningful.”
Here.
http://arctic.atmos.uiuc.edu/SEAICE/timeseries.1870-2008
Look at this precipitation prediction for Baffin Bay, the Inlet and Hudson Bay area (west of Greenland): http://wxmaps.org/pix/prec2.html
(thanks to the poster who provided the link today)
It’s been colder than a well diggers rear in the Arctic, and “problem” areas such as the Beufort/Laptev Seas area, the Barents/Kara Seas area and the Baffin Bay area have all seen fast ice growth in the last few days. No conditions are foreseen that would slow this progress to date, rather the signs point to continued growth if not acceleration. In the next few days to a week we are likely to see extent rising close to or exceeding the average. Hang on to your hats, this could get interesting.
MartinGAtkins (19:05:51) :
Tom in ice free Florida (15:11:40) :
“Now if we could just get the data to go back and start at 1907 it would be even more meaningful.”
Here.”
http://arctic.atmos.uiuc.edu/SEAICE/timeseries.1870-2008
Wow. Sea ice to 5 decimal points all the way back to 1870. I wonder where they keep their Tardis.
The data for sea ice all the way back to 1870 is almost too ridiculous. Are we so stupid that we will allow this rewriting of history? Who is responsible for THIS fiction? At what point will ALL data be suspect? I think we may have already reached that point.
Is science too far gone to be saved?
Mark Bryant -“The data for sea ice all the way back to 1870 is almost too ridiculous. ”
Is anyone really pretending to use this rubbish? Surely not? This has got to be some ratbag making a joke! Isn’t it?
Seems to be some difference between the above “extent” and AMSR from JAXA:
http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png
This shows “extent” a little under 8 million, which is different from both the Nansen “area” or “extent”, by roughly half a million either way. Nansen “area” is closer to AMSR “extent” than Nansen “extent”. Different algorithms perhaps.
Showing only plus and minus one standard deviation is not commonplace in error analysis. That range covers only about two-thirds of the outcomes in a Gaussian normal distribution. A better choice would have been the 95% confidence interval or about plus or minus 1.96 standard deviations. Had you done that the broader range might have included all of the 2008 figures and perhaps even some of the 2007 figures.
REPLY: The graphs are not mine, but are from Nansen Research Center. I have no control over the analysis, I was simply pointing them out. – Anthony
Around the southside
So cold that we cried
Were we ever colder on that day
A million miles away
It seemed from all of eternity
Graph from same site. Ice 1900-2007. The graph seems different after 1952; the International Geophysical Year wasn’t until 1957, so it’s not an IGY effect.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg
From: http://www.cgd.ucar.edu/cas/guide/Data/walsh.html
The above link appears to describe the sources of data for the sea ice in the Northern Hemisphere at http://arctic.atmos.uiuc.edu/SEAICE/timeseries.1870-2008 linked to above. Some selected quotes:
“Please note that large portions of the pre-1953, and almost all of the pre-1900 data is either climatology (?) or interpolated data and the user is cautioned to use this data with care (see “Expert user guidance”…”
“Temporal extension of Kelly ice extent analyses…Sea ice extent data is provided by Kelly, et. al. 1988. The ice extent data is compiled for the months April-August for the majority of the period 1901-1956.”
“We add a marginal sea ice zone to the Kelly ice extent data by computing average ice concentration drop-off rates for the period during which there are satellite observations.”
“Regional sea ice anomalies have been shown to persist (LTP?) for many months and even seasons (Chapman and Walsh, 1991). We attempt to capitalize on this persistence by extending the ice anomaly data from (1) forward and backward in time to fill in the months September-March for each year in the 1901-1956 period. … We have attempted to stretch the useful information included in the Kelly ice extent data to extract as much information as possible from the data. …”
“1972-1998: Satellite period – hemispheric coverage, state-of-the-art data accuracy
1953-1971: Hemispheric observations – complete coverage from a variety of sources. The observational reliability varies with each source, but is generally accurate.
1870-1952: Climatology (???) with increasing amounts of observed data throughout the period.”
“Because most of the direct observations of sea ice (1870-1971 period) are from ships at sea, they are generally the most complete near the ice edge. The conditions north of the ice edge are often assumed to be 100% covered during this period. The satellite era has shown otherwise…”
Question marks and emphasis added.
In my opinion, the authors of this database should be commended for their frank description of this dataset, although it is fair to question whether this dataset should have been constructed at all. There needs to be some definition of when in climate science it is appropriate to say that there isn’t enough data.
From: http://arctic.atmos.uiuc.edu/SEAICE/arctic.historical.seaice.doc.txt
The description of data sources for sea ice in the Northern Hemisphere is very similar to that in my post above. However, here are some additional quotes from language NOT included in my post above:
“..ice areas derived from pre-1978 data may be significantly higher than those calculated from the satellite period.”
“We urge you to pay special attention to the data sources and their limitations when using this data.”
One has to wonder if the very important caveat in my last quote above in bold ever has been or would ever be pointed out to policy makers as a matter of course concerning the issue of arctic ice.
‘REPLY: Nobody said a thing (except you) about it being “unprecedented”. I’m simply pointing out what a great recovery arctic sea ice is having. It’s funny that some people who have commented here don’t seem to like what is happening. – Anthony’
Well if no one said it, that is good, because what value is there in saying something that someone else has already said.
Just to be clear, I was pointing out that the recovery the ice is having is to a value that is comparable to what we had a few months ago.
I don’t have children
Sorry to be harsh, but the only thing that you will likely accomplish by this is to die alone and forgotten, and have missed out on the primary purpose for human existence.
On average, Muslim families have six children. Maybe they will build a Mosque where your house used to be.