6 September 2011

2011 Arctic Ice Reaches Second Lowest on Record- One or two weeks of melting left.

Posted by Dan Satterfield

The NSIDC updated the Arctic ice numbers today and announced that the ice melt has now reached the second lowest on the satellite record.


Overview of conditions
Average ice extent for August 2011 was 5.52 million square kilometers (2.13 million square miles). This is 160,000 square kilometers (61,800 square miles) above the previous record low for the month, set in August 2007, and 2.15 million square kilometers (830,000 square miles), or 28% below the average for 1979 to 2000. Sea ice coverage remained below normal everywhere except the East Greenland Sea. In addition, several large areas of open water (polynyas) have opened within the ice pack.

On August 31, 2011 Arctic sea ice extent was 4.63 million square kilometers (1.79 million square miles). This is 100,000 square kilometers (38,600 square miles) higher than the previous record low for the same day of the year, set in 2007. As of September 5, ice extent had fallen below the minimum ice extents in September 2010 and 2008 (previously the third- and second-lowest minima in the satellite record). If ice stopped declining in extent today it would be the second-lowest minimum extent in the satellite record.

Higher-resolution Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) data processed by the University of Bremen showed ice extent on September 5 as falling below the same date in 2007.

UAH lower troposphere satellite temp. estimates from J. Christy and R. Spencer at UA Huntsville.

UAH Satellite Record

Climate expert Dr. Ben Santer at Lawr. Livermore Nat. Labs pointed out in email today that “even the UAH TLT (lower troposphere temp) data now show a signal-to-noise ratio of nearly 4 for global-scale changes in lower tropospheric temperature over the satellite era. In other words, UAH’s lower tropospheric warming is four times larger than our current best estimates of climate noise on the 32-year timescale.”

If this is confusing, think of this way: the signal to noise ratio is comparing the natural fluctuations you would expect to see in the lower atmosphere (over a 32 year period) with the actual data from the satellites. We know that weather happens, and this kind of analysis is a way of making sure that the warming seen is not a natural fluctuation.

Ben Santer explains it this way much better: “We are looking at the “signal” (the observed lower troposphere temperature change) and the “noise” (the unforced (no greenhouse effect variability estimated from model runs with no changes in external forcings) on the same timescale. So we are comparing the observed 32-year increase in Temperatures in the lower troposphere with model estimates of natural fluctuations on the 32-year timescale.”

I try to write this blog for those who have no science background so if your response is well duh!- please understand. The short version is that the myth that the satellites do not show as much warming globally as the surface temperature record is long gone. There are still some inconsistencies, but they are most likely mainly from the difference in methods used to gather the data of both sets. Dr. Santer has a new paper out that dispels another claim recently made in testimony to Congress.

More on that soon.

Note I revised my explanation (oversimplified) and added Dr. Santer’s additional comments from the initial post.