Sunday, September 14, 2014

New paper predicts Antarctica will only contribute a tiny -.87 to +2.5 inches of sea level rise by 2100

A new paper published in Climate Dynamics models the future contribution of the Antarctic ice sheet to global mean sea level in 2100 and predicts a range from a decrease in sea level [due to ice accumulation] of -22 mm or negative 0.87 inches to a slight increase in sea levels of 63 mm or 2.5 inches. The median of this range is a tiny 1.6 inches of sea level contribution from Antarctica by the year 2100, hardly of concern.

Further, this estimate based upon conventional climate model assumptions of climate sensitivity to CO2, falsified as exaggerated at confidence levels exceeding 98%. 

The authors also conclude that "sea-level change has driven the deglaciation of the ice sheet" over the past 21,000 years since the peak of the last ice age. Global sea levels have been naturally rising for ~20,000 years and have decelerated over the past 8,000 years, decelerated over the 20th centurydecelerated 31% since 2002 and decelerated 44% since 2004 to less than 7 inches per century. There is no evidence of an acceleration of sea level rise, thus no evidence of any effect of mankind on sea levels. Since sea-level rise is not man-made, and based upon the findings of this paper, there is therefore no evidence of any effect of man on Antarctic glacier loss in the past. 

Antarctica holds over 80% of the ice on Earth, with most of the remainder in the Greenland ice sheet, which has also been demonstrated to be resistant to thaw and "insensitive" to surface melting from warming, thus further lowering sea level rise projections. Lowered sea level contributions from both Antarctica and Greenland effectively call off the alarm on future sea levels. 

A model study of the effect of climate and sea-level change on the evolution of the Antarctic Ice Sheet from the Last Glacial Maximum to 2100

M. N. A. Maris, J. M. van Wessem, W. J. van de Berg, B. de Boer, J. Oerlemans

Due to a scarcity of observations and its long memory of uncertain past climate, the Antarctic Ice Sheet remains a largely unknown factor in the prediction of global sea level change. As the history of the ice sheet plays a key role in its future evolution, in this study we model the Antarctic Ice Sheet from the Last Glacial Maximum (21 kyr ago) until the year 2100 with the ice-dynamical model ANICE. We force the model with different temperature, surface mass balance and sea-level records to investigate the importance of these different aspects for the evolution of the ice sheet. Additionally, we compare the model output from 21 kyr ago until the present with observations to assess model performance in simulating the total grounded ice volume and the evolution of different regions of the Antarctic Ice Sheet. Although there are some clear limitations of the model, we conclude that sea-level change has driven the deglaciation of the ice sheet, whereas future temperature change and the history of the ice sheet are the primary cause of changes in ice volume in the future. We estimate the change in grounded ice volume between its maximum (around 15 kyr ago) and the present-day to be between 8.4 and 12.5 m sea-level equivalent and the contribution of the Antarctic Ice Sheet to the global mean sea level in 2100, with respect to 2000, to be −22 to 63 mm.

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