Oceanographer Wieslaw Maslowski of the Naval Post-Graduate School made a boding prediction recently that we may have hit the Global Warming tipping point which will result in a complete loss of multi-year ice in the Arctic sometime between 2010 and 2016. He states that recent measurements of ice extents in the Arctic show an accelerated loss of ice volume driven by global warming.
There are several important issues that need to be considered regarding short term observations before we run off with poorly substantiated predictions. They are:
1) Maslowski’s predictions are considered to be worst case by many of his peers. As such, his commentary should be viewed as noteworthy but not necessarily predictive.
2) The NSIDC announced publically that their ice extent measurements were off, indicating approximately 500,000 sq. km. less ice for the past several months due to sensor drift, ultimately sensor failure, and data drop-outs. That the NSIDC made this announcement openly and immediately on discovery, in my opinion, testifies favorably to their integrity.
Real-time data products such as those offered by the NSIDC are, well, real time and subject to sensor and data errors. They require correlation and verification with other references - a time consuming process that can take up to a year. Anyone who makes predictions based on any short term data does so at their own professional risk. Maslowski doesn’t comment on his source data or validation methods so it is hard to know if NSIDC data errors have any bearing on his conclusions. Given the timing of his prediction and the emphasis on recent measurements, I suspect they do.
3) Over the past 250 years of ground based measurements, there have been four distinct periods where the ice extents rapidly receded then subsequently recovered. These lower ice extent periods last one or more decades and are attributed to natural climate fluctuations. In the recent past, the western Arctic Ocean was much warmer than it is today (3-7 deg warmer).
4) Climatologists are citing relatively recent discovery of the Pacific Decadal Oscillation and accompanying wind pattern changes as being responsible for the lower ice extent being observed. Current Arctic climate observations do not support amplified warming in Polar Regions predicted by GCMs [General Circulation Models]. Specifically, wind patterns have been blowing normal seasonally broken up ice packs out of the basin to warmer open waters, resulting in lower ice volume measurements. The effects of this ice flow pattern were mentioned by Maslowski in a recent highly publicized interview. However, the cyclical history of the pattern seems to have been conveniently omitted by Maslowski.
The bottom line is while some like Maslowski suggest that we crossed the tipping point (or are on the verge), there is no body of evidence to substantiate the claim or even give it reasonable plausibility.