A commenter on another site pointed to this Hudson GRL 2011, which attempted to answer this very question with better science by including changes in cloud cover and the seasonal variation of solar radiation.
He concludes that the increase in forcing due to Arctic sea ice over the period 1979-2007 is about 0.1 W/m2. (My estimate was 0.12 W/m2, which was closer than it deserved to be.)
By comparison, manmade CO2 forcing is now about 1.8 W/m2, and the forcing from all manmade GHGs is about 2.8 W/m2.
(Incidentally, that means, if you lump all GHGs into a CO2-only picture, the effective atmospheric CO2 level is about 470 ppm, as of 2010.)
Hudson finds
"...a complete removal of Arctic sea ice results in a forcing of about 0.7 W m−2, while a more realistic ice-free-summer scenario (no ice for one month, decreased ice at all other times of the year) results in a forcing of about 0.3 W m−2, similar to present-day anthropogenic forcing caused by halocarbons. The potential for changes in cloud cover as a result of the changes in sea ice makes the evaluation of the actual forcing that may be realized quite uncertain, since such changes could overwhelm the forcing caused by the sea-ice loss itself, if the cloudiness increases in the summertime.Marc Morano and Steve Goddard are desperately trying to distract attention by highlighting the gain in Antarctic sea ice. The problem, of course, is that the Arctic is melting much faster than the Antarctic is gaining ice: -54 Kkm2/yr compared to +14 Kkm2/yr, since the beginning of satellite records.
Added: Then there is the fact that Arctic sea ice tends to be thicker than Antarctic sea ice: about 2-3 meters versus 1-2 meters, says the NSIDC. So a loss of a square meter of Arctic sea ice is a larger volume loss than is the volume gain of an Antarctic square meter of sea ice.
10 comments:
When you consider the uncertainty in sea ice measurement of +/-20%, there has been no change in global sea ice since satellite measurements began in 1979/80. The Antarctic change (+ve) is not large enough to compensate completely for the Arctic drop, but, when you consider the uncertainty in measures, it is.
Sincerely,
Tom Harris
Executive Director
International Climate Science
http://www.climatescienceinternational.org
Who says the uncertainty is 20%?
The trend of global sea ice since the satellite era is -40 +/- 3 Kkm2/yr (1-sigma statistical uncertainty)
Tom, that's a crazy assertion. Methodologies for assessing satellite data are standardised, so any uncertainties are known and consistent from year to year.
The trend is down with certainty.
The IPCC's AR5 Working Group 1 has found the global rate of ice sheet melting to be roughly 300 Giga-tonnes per year. That sounds like a really scary number until you ask a simple question.
What is the global ice sheet volume? The answer is >30 million Giga-tonnes. At the current rate of melting it will take 100,000 years to melt it all.
The glaciers in the Rocky mountains are receding but they still exist in places that were ice free 5,000 years ago. I wonder what caused "Global warming" back then?
Get used to it, ice comes and ice goes. No big deal.
Only dolts and halfwits fall for the...erm..."arguments" in bahamamama's comments.
Smarter industry sockpuppets please. They used to be of much better quality. Now they are more like Internet Performance Art parody characters.
Best,
D
Dano,
Please read this:
http://davidappell.com/AR5/ZODS/WG1AR5_ZOD_Ch04_All_Final_cryosphere.pdf
Your response may help me determine what kind of ostrich you are.
Your response may help me determine what kind of ostrich you are.
The industry sockpuppets used to hide their mendacity much better than this current crop. Maybe it is the decade+ of using the same arguments over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and v over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over and over.
We report, you decide.
Best,
D
Dano,
Thanks for that.
You are now officially a "Juvenile" ostrich.
In another six or seven years you may be mature enough to have a lucid discussion with grown ups.
We talk about how the industry sockpuppets haven't brought anything new in years, and the disinformation firms can't seem to find talent these days.
Best,
D
If we accept, for the sake of argument, as Tom Harris suggests, sea ice measurements are really that inaccurate, then the 2012 minimum might have been grossly overestimated, meaning that we are closer to an ice free Arctic than anyone thinks.
But I doubt that was the point he was trying to make...
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