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Last Glacial Maximum and Little Ice Age Atmospheric Circulation Characteristics Over the Mediterranean Sea
Reference
Kuhlemann, J., Rohling, E.J., Krumrei, I., Kubik, P., Ivy-Ochs, S. and Kucera, M. 2008. Regional synthesis of Mediterranean atmospheric circulation during the Last Glacial Maximum. Science 321: 1338-1340.

What was done
The authors developed a synthesis of vertical temperature gradients in the lower atmosphere of the Mediterranean region during the Last Glacial Maximum (LGM, about 19 to 23 thousand years ago), based on equilibrium line altitudes of the area's glaciers, which can be reconstructed by in situ dating of glacial advances and retreats, augmented by information provided by sea surface temperature proxies, after which they compared their results with what has been learned about the region's atmospheric circulation during the Little Ice Age, from which the world was rescued by 20th-century global warming.

What was learned
Kuhlemann et al. say their synthesis "reveals evidence for frequent cold polar air incursions, topographically channeled into the northwestern Mediterranean," and that "anomalously steep vertical temperature gradients in the central Mediterranean imply local convective precipitation," noting that "a similar configuration is thought to have been common during the late Little Ice Age, notably the Maunder Minimum," when there was "enhanced meridional winter circulation." On another note, they also report that their findings "do not support a straightforward zonal LGM atmospheric circulation, as inferred from climate models."

What it means
The results of this study have two important implications. First, they suggest that current climate models are not up to the task required of them (i.e., providing climate simulations that are good enough to drive energy policy development), as they fail to properly portray the past. Second, they suggest that the Little Ice Age was likely the coldest period of the current interglacial, which further suggests it should not be surprising that the earth has warmed as much as it has in response to the increase in solar activity that followed the demise of the Maunder Minimum, starting (as the past century's warming did) from such a uniquely-cold base-level temperature.

Reviewed 17 December 2008