Written by Nils-Axel Mörner
With very great pleasure did I consume the paper by Faezeh et al. (2013) just printed in Nature (May 9). After a careful study of four major marine-terminating outlet glaciers,collectively draining 22% of the Greenland Ice Sheet, they were able to estimate the annualdynamic losses at volumes corresponding to a mean global sea level rise of 0.01–0.06 mm peryear. In 100 years this would only give a sea level rise on 1-6 mm, which is insignificant. Byapplying a hypothetical future warming or 2.8 oC they increase this value to 19–30 mm rise by year 2200 (or about 9-15 mm by year 2100). Even this value is so low that it poses nothreat what so ever to humanity.
What was it I said, I may say referring to numerous previous papers of mine, but especially the paper on “Setting the frames of expected future sea level changes” (Mörner, 2011), where the problem of the contribution of glacial melting is specially addressed (Fig. 1).
During the Holocene Climatic Optimum with a temperature 2.5 oC higher than today, theGreenland ice cap seems to have been of roughly the same dimensions as today. The Little IceAges of the last 600 years with significantly larger glaciers had small to insignificant effectson mean global sea level. A sea level rise of today would never stay a chance to exceed that ofthe main melting phase at the end of the Last Ice Age which amounted to about 10 mm year-1 (i.e. 1.0 m in 100 years); on the contrary, it would have to be well within these frames.
Now, we can see that the present day melting of the Greenland Ice Cap provides sea leveleffects that are minute to negligible and fall well within the values of about 1 mm year-1 (Fig.1) recorded during the last 300 years (Mörner, 2004).
Faezeh, M.N., Vieli, A., Andersen, M.L., Joughin, I., Payne, A., Edwards, T.L., Pattyn, F. & van de Wal, R.S.W., 2013. Future sea-level rise from Greenland’s main outlet glaciers in a warming climate. Nature, 497, 235-238.Mörner, N.-A., 2004. Estimating future sea level changes. Global Planetary Change, 40, 49-54.
Mörner, N.-A., 2011. Setting the frames of expected future sea level changes. In:Evidence-based Climate Science, D.J. Easterbrook, Ed., Chapter 6, 197-209, Elsevier.
Fig. 1. Introduction of the new values on the Greenland ice melting contribution to global sealevel by Fraezeh et al. (2013) into the figure by Mörner (2011) on rates and amplitudes ofexpected future changes in sea level with the frame of physically possible changes set at 10 ±1 mm year-1 or 1.0 ±0.1 m in a century, and with the observed rate of changes in the last 300years of 1 mm year-1 or 10 cm in a century.