Yep, looks like the ice area is shrinking. Do you have access to any records that go back further than a few years? Like 10,000 years? 1 million? I realize we weren't getting satellite shots a million years ago, I just wondered if we can put the current trend into a little broader perspective.

Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier.....[ice] consistently covered at least part of the Arctic Ocean for no less than the last 13–14 million years. .....The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.

There weren't any humans around a million years ago or coastal cities and mass agriculture trying to feed 9 billion people 10,000 years ago so it is irrelevant from a human perspective. The fact that tens of millions of years ago sea ice was less than today in no way is going to help us cope with the ice free climate we are creating for the coming decades.

Occam wrote:


That's not the reason for my question. It's not irrelevant if you are trying to determine if this reduction in ice is unusual, or if it has anything to do with the actions of humans, or indeed if it's truly a bad thing from a feed-the-humans perspective. Maybe "we" aren't creating an ice-free climate, maybe it's just happening because this is what Earth does. Maybe we can start farming on Greenland again soon. Those are relevant questions to humans IMO.

Prediction alert!


It looks like another very low extent this year, but a new record is unlikely. I think a new record low is highly unlikely next year as well; but I'd give each of the five years thereafter a 1 in 5 chance of setting a new record low ice extent, every year will have a lower extent than 2000, and am highly confident we will have at least one new record low within the next decade.

Interesting. could play havoc with my 2028 prediction

www.sciencedaily.com/releases/2011/08/110811113956.htm

There is a new paper which is critical of the ERA-40 Reanalysis. This is an important issue as this data set has been used in long-term climate studies; e.g. see which has over 2000 citations in the peer-reviewed literature according to google scholar. The new paper is
Screen, James A., Ian Simmonds, 2011: Erroneous Arctic Temperature Trends in the ERA-40 Reanalysis: A Closer Look. J. Climate, 24, 2620–2627. doi: 10.1175/2010JCLI4054.1.


The abstract reads [highlight added]

“Atmospheric reanalyses can be useful tools for examining climate variability and change; however, they must be used cautiously because of time-varying biases that can induce artificial trends. This study explicitly documents a discontinuity in the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) that leads to significantly exaggerated warming in the Arctic mid- to lower troposphere, and demonstrates that the continuing use of ERA-40 to study Arctic temperature trends is problematic. The discontinuity occurs in 1997 in response to refined processing of satellite radiances prior to their assimilation into the reanalysis model. It is clearly apparent in comparisons of ERA-40 output against satellite-derived air temperatures, in situ observations, and alternative reanalyses. Decadal or multidecadal Arctic temperature trends calculated over periods that include 1997 are highly inaccurate, particularly below 600 hPa. It is shown that ERA-40 is poorly suited to studying Arctic temperature trends and their vertical profile, and conclusions based upon them must be viewed with extreme caution. Consequently, its future use for this purpose is discouraged. In the context of the wider scientific debate on the suitability of reanalyses for trend analyses, the results show that a series of alternative reanalyses are in broad-scale agreement with observations. Thus, the authors encourage their discerning use instead of ERA-40 for examining Arctic climate change while also reaffirming the importance of verifying reanalyses with observations whenever possible.”

Text in the paper includes

“ERA-40 has been recently used to assess Arctic temperature trends and their vertical structure. Most notably, ERA-40 formed the basis of a now-controversial examination of central Arctic temperature trends by Graversen et al. (2008). The results of that study have been strongly contested, mainly because of concerns about the accuracy of trends calculated from ERA-40 temperatures (Bitz and Fu 2008; Grant et al. 2008; Thorne 2008; Screen and Simmonds 2010b). Yet, ERA-40 continues to be used for Arctic temperature trend analysis (e.g., Yang et al. 2010). In light of this, we show here—explicitly and more thoroughly than previous studies—that inhomogeneities in ERA-40 lead to a poor representation of Arctic temperature trends, particularly in the mid- to lower troposphere, and we demonstrate that its continued use for this purpose is problematic.”

Such an error not only affects the Arctic troposphere, but necessarily must effect the entire northern hemisphere jet stream. It is the poleward to equatorward layer average temperature gradient which causes this wind, as we discuss, for example, in

A paper published today in the Journal of Atmospheric and Oceanic Technology finds that temperature measurements on the Antarctic plateau "are shown to be significantly warm biased by solar radiation," resulting in temperature measurements up to 10°C (18°F) warmer than actual temperatures. The authors find that the summer Sun heats the housing for the electronic thermometers causing the warming bias during summer, which is also exacerbated by low wind conditions. Surface temperature measurements are particularly important at the poles, because satellite measurements of temperature do not include data poleward of 82.5° North and 70° South and the only available measurements in these areas are from surface temperature stations. Considering the tiny change in global temperature over the past 161 years of only 0.7°C, this newly-discovered large warming bias of up to 10°C calls into question data from areas critical to the AGW debate.

Identical Story – Different Century
www.msnbc.msn.com/id/33437613/ns/us_news-environment/


docs.lib.noaa.gov/rescue/mwr/050/mwr-050-11-0589a.pdf




Hundreds more available.