A Comment On A 1999 Paper “Global Warming And Northern Hemisphere Sea Ice Extent By Vinnikov Et Al

Ten years ago, the following paper was published.

Vinnikov et al., 1999: Global warming and northern hemisphere sea ice extent. Science. 286, 1934-1937.

In this paper, there is a presentation of the model predictions of sea ice extent along with observations up to 1998.  This weblog introduces the subject of how well have the model predictions done.

Their abstract includes the statement (referring to the GFDL and Hadley global climate models)

“Both models used here project continued decreases in sea ice thickness and extent throughout the next century.”

In the conclusion to their paper, they write

“Both climate models realistically reproduce the observed annual trends in NH sea ice extent. This suggests that these models can be used with some confidence to predict future changes in sea ice extent in response to increasing greenhouse gases in the atmosphere. Both models predict continued substantial sea ice extent and thickness decreases in the next century.”

In their paper (in Table 1) they have model predictions (in units of linear trend in 106 square kilometers per decade) listed for the GFDL climate model from 1978-1998 of -0.34 (and -0.19 using a “smoothed model output“) and for the Hadley Centre climate model -0.18 (and -0.16 using a “smoothed model output“).

A value of -0.18 is the loss of sea ice area of 180000 square kilometers per decade, for example.

The first figure below is from the Vinnikov et al 1999 paper  with respect to the model predictions, while the second and third figures are the sea ice areal anomaly and the sea ice areal converage for the Northern Hemisphere up to the present from The Cryosphere Today.



From: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.jpg

Until later in 2007, the sea ice areal extent continued to decrease in a manner which, at least visually, is consistent with the Vinnikov et al 1999 predictions (although the actual values of areal coverage differ substantially between the observations and the predictions, perhaps as a result of their formulation to compute areal coverage).

However, since 2006, the reduction has stopped and even reversed. Perhaps this is a short term event and the reduction of sea ice extent will resume. Nonetheless, the reason for the turn around, even if short term, needs an explanation.  Moreover, this data provides a valuable climate metric to assess whether the multi-decadal global models do have predictive skill as concluded in the Vinnikov et al 2009 paper.

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