Greenland Ice Mass loss estimates for 2012

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  1. hunter

     /  27/06/2013

    With all respect, and out of respect to skeptics, please admit to your error, fix it, and be transparent about it. Soon, please.

    • manicbeancounter

       /  27/06/2013

      Just posted to WUWT

      Further to earlier comment, the source of my confusion is the between this statement in Velicogna and Wahr 2006:-

      A fit to the GRACE results for all Greenland before and after April 2004 yielded ice loss trends of 104 +/- 54 km3 yr-1 during April 2002–April 2004, and 342 +/- 66 km3 yr-1 during May 2004–April 2006.

      This after having earlier read the later papers like Rignot et al 2011, which states:-

      In 2006, the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise. Notably, the acceleration in ice sheet loss over the last 18 years was 21.9 ± 1 Gt/yr2 for Greenland and 14.5 ± 2 Gt/yr2 for Antarctica, for a combined total of 36.3 ± 2 Gt/yr2.

      The earlier paper did not state acceleration, but a step change in annual rate. I saw acceleration in the graph and therefore saw acceleration in the words. Unfortunately I had not cross-checked the words in the paper with the maths. I apologise again for the confusion caused.

      However, even as a cumulative, the graph appears to show a year-on-year acceleration. From the statement above, the total change over the 4 year period is 2(-104-342) = -892. Multiply this by 10/4 and you get a cumulative decadal loss of -2230 on the graph. In mid-2006 the hand-drawn trend is around -700. The last 4 years (mid- 2008 to mid-2012) have a cumulative loss of about double that. Therefore, although I have mistaken annual for cumulative, there are still two sub-issues here I state in a longer article on my blog.
      First is about using old research, when more recent and higher quality research is available. This is particularly the case when projecting forward from actual data. Second, is about observing discontinuities in a short period, and modelling a trend. Like many other aspects of climate, changes in ice mass are hugely difficult to measure and highly variable year-on-year.

      Kevin Marshall

  1. NOAA exaggerates 2012 Greenland Ice Mass Loss by 10x | Watts Up With That?

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