The Garnaut Review states (page 13):
If the Greenland ice sheet were to melt, it would add about seven metres to the world’s ocean, and the west Antarctic ice sheet up to six metres, over a long period.
However, the Garnaut Review does not specify the time scale meant by “over a long period”.
Satellite data indicate sea level rise of 3.3 mm/yr during 1993-2006. Since 1990 the observed mean global sea levels have been rising faster than projected by IPCC models.
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Over the last 20 years the rate is 25 percent faster than the rate in any twenty years period in the preceding 115 years (Rahmstorf et al., Science Express, 2007, Potsdam Institute of Climate Impact Research, 2007).
Leading climate scientists, including Professor James Hansen (NASA’s chief climate scientist) and Professor Steffen Rahmstorf (Potsdam Institute of Climate Impact Research), project sea level rise on the scale of metres through the 21st century. Paleo-climate studies by Glikson and Brook (submitted to Geosphere) indicate sea level rise rates of well over 5 metres per 1 degree C, consistent with these projections.
Sea level rises reflect melting of the Greenland ice sheet, where melting since measurements began in 1979 increased by 30 percent (S. Konrad, University of Colorado, AGU, 2008), and of the west Antarctica ice sheet which is losing ice at rates 60 percent faster than 10 years ago (British Antarctic Survey, Nature Geoscience, 2008).
Given the consequences of sea level rise around the world in terms of inundation of cultivated delta, coastal and lower river regions, where hundreds of millions of people live, and the flooding of port cities, including major Australian coastal cities, the warnings presented in the Garnaut Review would appear to underestimate of the global effects of sea level rise, should the levels of greenhouse gases in the atmosphere and associated carbon cycle feedbacks continue to rise.