Arctic sea ice coverage now at 6th-lowest extent in millennia
Part 1 of 2 reports on this webpage
by Dana Nuccitelli
Average July through September Arctic sea ice extent 1870–2008
As a result of anthropogenic climate warming, the extent of the Arctic's characteristic sea ice collapsed from 1979 to 2012, several decades ahead of the predictions of climate models, as documented here. Arctic sea ice now (Autumn 2013) appears to have reached its annual minimum extent, at approximately 5.1 million square kilometres. This is the 6th-lowest extent since the satellite record began in 1979.
Scientists have also reconstructed Arctic sea ice extent data much further into the past. Walsh & Chapman from the University of Illinois have estimated sea ice extent as far back as the year 1870 using a vast array of data (e.g. records kept by the Danish Meteorological Institute & Norwegian Polar Institute, plus reports from ocean vessels, as shown in the following figure).
Going back even further in time, a study published in the journal Nature in 2011 used a combination of Arctic ice core, tree ring, and lake sediment data to reconstruct Arctic conditions going back 1,450 years. A study published in 2010 by 18 leading Arctic experts examined Arctic records throughout geologic history, concluding:
"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."
Thus the scientific data and literature indicate that this year's minimum Arctic sea ice extent is not just the 6th-lowest in the past 34 years, but most likely the 6th-lowest in at least the past few thousand years.
The current Arctic sea ice decline is remarkably rapid, and often referred to as a "death spiral." The body of scientific research clearly shows that this rapid decline is due to human influences on the climate.
◊ Dana Nuccitelli is an environmental scientist & risk assessor who contributes to SkepticalScience.com Publ. here 20.9.2013
CryoSat satellite reveals ongoing
decline in Arctic sea ice volume
Part 2 of 2 reports on this webpage
by Joe Romm
The CryoSat satellite allows very accurate measures of ice thickness, which can be combined with ice area to give volume. Measurements taken between October 2010 and April 2013 reveal that “the volume of seasonal winter and summer sea ice has declined year on year during this period.” University of Leeds Prof. Andrew Shepherd explains:
“CryoSat continues to provide clear evidence of diminishing Arctic sea ice. There has been a decrease in the volume of winter and summer ice over the past three years…The volume of the sea ice at the end of last winter was lower than any other year going into summer and indicates less winter growth than usual.”
With respect to the Arctic sea ice, then, we are not discussing a (literal = aviation type) "death spiral". We are applying the following “idiomatic” definition of this term with respect to Arctic sea ice decline:
The situation or course of action of one who is on a path toward some sort of inevitable catastrophic failure.
◊ Joe Romm is the leading scientific blogger on climate. Publ. here 19.9.2013