Portrait of a Meltdown: Many factors led to 2007's record low in

Arctic sea ice

http://www.sciencenews.org/view/generic/id/9236/title/Portrait_of_a_Meltdown_Man\

y_factors_led_to_2007s_record_low_in_Arctic_sea_ice

Excerpt:

"An adverse combination of factors contributed to this year's steep

decline, researchers noted last week at a meeting of the American

Geophysical Union in San Francisco.

First, a long-term trend in thinning and shrinkage of Arctic ice set

the stage for this year's meltdown, says Jinlun Zhang, an

oceanographer at the University of Washington in Seattle.

End-of-summer ice coverage has been declining by about 11.4 percent

per decade since 1979. Also, average ice thickness decreased by about

1.13 meters, or 22 percent, between 1981 and 2000.

Second, Zhang notes, unusually strong summer winds pushed much of the

ice out of the central Arctic, leaving a large area of thin ice and

open water. Third, a decrease in cloud cover in the Arctic "a trend

suspected but not confirmed earlier this year (SN: 6/16/07, p.

382) "allowed more sunlight to reach the ocean. Because open water

absorbs more of the sun's radiation than snow-covered ice, it

significantly boosts warming trends both for the ocean and for the

atmosphere above it (SN: 11/12/05, p. 312). This so-called ice/albedo

feedback accelerated this year's melting, says Zhang."

Less cloud cover = more sunlight = less ice cover. While there is a

long term trend in the Arctic 2007 was an aberration, and 2008 Arctic sea ice recovered dramatically, by more than a million sq km. 

Ocean heat content (not just SST's) has shown a slight cooling in recent years. Josh Willis of NASA who authored the ARGO studies discussed this with Roger Pielke Sr. last year.

http://climatesci.org/2008/05/29/new-information-from-josh-willis-on-upper-ocean-heat-content/

Dr. Willis talks about how cooling from melting ice and other factors probably should "add at least a few more tenths of a W/m^2 to the errorbar on this 4-year warming rate". But it's too small a factor to offset the ocean warming that should have been added by the several W/m^2 forcing of GHGs, but is not seen in the data.

In discussing the Ocean Heat Content issue Pielke Sr. commented:

"The analysis being completed by Josh Willis and colleagues is central to the issue of assessing global warming and cooling. Climate Science recommends that upper ocean heat changes in Joules become the primary assessment tool for global climate system heat changes, as the data, with the introduction of the Argo network, is now robust to this evaluation. "

And that is the point. Opinions may be swayed by articles on melting ice, however science must evaluate real data such as measured OHC to assess climate change.

Cheers

Jim

part of a debate in progress in Yahoo Group ClimateConcern