Wednesday
Mar242010
by 
Bishop Hill
Bishop Hill Global sea ice normal
Mar 24, 2010 Climate: HSI 
Global sea ice levels are pretty much in line with their long-term average. (Source: Cryosphere Today)
Mar 24, 2010 Climate: HSI
Reader Comments (61)
'....The Antarctic (for example) doesn't really do sea ice. It's a different environment....- Cedric
The Cryosphere Sea Ice Area charts suggest that the SH (1979-2000 mean) annual maximum is about 15 million sq klms.
SH - 15 million sq klms - seems to be rather good at doing something it 'doesn't really do'.
This is brazen misinformation. If you want to actually know what is going on (I suspect you don't, buy anyway), you need to go to the World Glacier Monitoring Service, based in Switzerland. Here's the latest figures, which clearly show glacier's of all kinds, not just sea ice are in retreat, as would be expected from higher levels of CO2 were trapping more heat in the atmosphere:
http://www.geo.unizh.ch/wgms/mbb/mbb11/preliminaryMB_2008_fig1.pdf
Don't know where those illinois students got their figures, but they're wrong. Or, of course, the WGMS could be part of the global communist conspiracy by sinister scientists and tree huggers to stop you driving your big Hummer....
TC
Firstly calm down.
Secondly, the posting is about sea ice not glaciers. You add nothing by posting a link to an article about the latter.
SH - 15 million sq klms - seems to be rather good at doing something it 'doesn't really do'.
This isn't hard to understand.
The Arctic and the Antarctic are...different.
Sea ice in the Arctic is different from sea ice in the Antarctic.
The Antarctic (for example) doesn't really do sea ice. It's a different environment....
Yep.
That's according to the science.
Why don’t I hear much about Antarctic sea ice?
NSIDC scientists do monitor sea ice in the Antarctic, and sea ice in the Antarctic is of interest to scientists worldwide. While many have published peer-reviewed journal articles on the topic, it has received less attention than the Arctic. There are several reasons for this.
Unlike Arctic sea ice, Antarctic sea ice disappears almost completely during the summer, and has since scientists have studied it. Earth’s climate system over thousands of years has been "in tune" with this annual summertime disappearance of Antarctic sea ice. However, satellite records and pre-satellite records indicate that the Arctic has not been free of summertime sea ice for at least 5,500 years and possibly for 125,000 years. So Earth’s climate system and ecosystems, as they exist today, did not develop in conjunction with an ice-free Arctic. Such an ice-free Arctic summer environment would be a change unprecedented in modern human history and could have ramifications for climate around the world.
From the National Snow and Ice Data Center.
How is sea ice extent changing?
Satellite measurements show the average annual sea ice extent in the Arctic has declined by 2.9% per decade since 1979, while summer extent has decreased by 11% per decade.
In Antarctica the changes have been much more subtle and regionally variable. The western Antarctic Peninsula region has shown a decline in sea ice extent, particularly in the Bellingshausen Sea, consistent with the recent change to more northerly winds and surface warming observed there.
In contrast, sea ice in the Ross and Weddell seas is increasing. These changes involve both changes in sea ice extent and in the length of season during which sea ice is present each year.
Taken from the Australian Antarctic Division
You don't have to rely upon a single graph and then struggle to understand it by yourself.
That's a great way to get things badly wrong.
That's how George Will did it and ended up confusing himself and others.
The scientists who made the graph are happy to explain their work and give the appropriate background and context.
Some people have even taken the time to create easy-to-understand videos to illustrate the science.
NASA has a really, really simple video on the issue. Really simple.
Still don't get it?
Ok. Here's another one.
2009 Sea Ice Update
Global sea ice is a curious critter. When the Arctic sea ice declines, the Antarctic sea ice advances, and vice versa. Go figure.
That's why Bishop Hill is right to look at global ice area, and not just one pole or the other. It's like looking at a guy pouring water from one glass to another and back again ... watching just one glass tells you nothing about the amount of water he has.
I have posted a graph of global sea ice area here. It shows global sea ice area for the period 1982-present. I have shown two different global sea ice datasets. One is the Hadley Centre's HadISST1 dataset, and the other is the Reynolds Optimal Interpolation V2 dataset. Both of them are available here.
Note that there is almost no change in the global sea ice area over the entire period. Not only is the global sea ice normal now, it has been normal for the last quarter century.
As Mark Twain said, "The rumors of my death have been greatly exaggerated" ... and the same is true of the sea ice. So please, spare us the horror stories about the Arctic. Globally, the sea ice area is basically unchanged.
Oh, couple more things. I didn't show the NSIDC ice area figures in the chart because they are virtually identical with the HadISSt1 figures. The correlations NSIDC/HadISST1 are:
Arctic: 0.995
Antarctic: 0.999
As a result, adding NSIDC figures to the chart would merely hide the HadISST1 figures. The conclusion from the NSIDC figures is exactly the same as from the other two datasets, however:
Global sea ice area has changed very little, either up or down, in the last quarter century.
Finally, the NSIDC spokesmodel quoted by Cedric Katesby above is playing a bit fast and loose with the facts when he says:
Minimum Antarctic sea ice is less than minimum Arctic sea ice, that's true. But maximum Antarctic sea ice is more than maximum Arctic sea ice.
The Arctic ice area swings from about 5 million to 14 million square km.
The Antarctic ice area swings from about 2.5 million to 16 million square km.
So the claim that Antarctic ice "disappears almost completely during the summer" is not borne out by the facts. Two and a half million square km. is the land area of the state of Alaska ... plus the area of Texas ... plus the area of California ... "disappears", indeed.
This is why I run the numbers myself, because the guardians of the climate facts often seem to be more concerned with making a point than with telling the truth.
Regarding area versus volume of sea ice, it would seem reasonable to assume that they are highly correlated. Regardless, I suggest that surface area is more important due to its relationship to albedo.
If I may speculate, CO2 warmists are invoking volume simply because area is contradicting them, and uncertainty in volume provides some shelter (however false and temporary).
Soon, there will be a new satellite to monitor and measure the thickness and extent of polar land and sea ice.
Delayed in February, because a fuel reserve problem in the launcher's second stage, the European Space Agency will attempt to launch CryoSat-2 on 8 April from the launch complex near Baikonur, Kazakstan. (Since 1993, Russia has rented the complex from Kazakstan. Sputnik and Gagarin were launched from there.) CryoSat-1 exploded soon after launch in 2005.
Using a Synthetic Aperture Interferometric Radar Altimeter (SIRAL), CryoSat's aims are to provide precise measurements on the thickness of floating sea ice and the ice sheets of Greenland and Antarctica..
http://www.esa.int/SPECIALS/Cryosat/SEMIOT9KF6G_0.html
The alarmists don't only need to demonstrate that the sea ice has reduced, they also have to demonstrate that it has reduced more than the medieval warm period or roman warm period. The glacier retreat the same, and it has to be statistically significant. The alarmists have a theory all of which has to be true to be accepted. The termperature history of the world has to be agreed without relying on a couple of trees for centuries at a time. The rather alarming correction for UHI which appears to exaggerate the effect rather than reduce it needs explaining or correcting. The failure of the well funded scientists to come up with a decent counter argument to either of these claims is frankly breathtaking. If the sea ice were the minimum for 30 years that would not be surprising when coming out of a little ice age. The fact the alarmists did not mention the Antarctic becuase the direction was wrong just demonstrates they are not as open-minded as they claim to be.
Who knows what the "natural extent" is? 30 years is too short. The September trendline has R-squared of about 0.47 - the trend is statistically meaningless.
+50