Background
Understanding natural climate variability is of great importance for many reasons, especially when one considers the powerful influence climate can exert on the social, cultural and economic landscape over short and long timescales.  It is also of critical importance in the search for evidence of anthropogenic-induced 20th-century climate change.  If it can be shown, for example, that climate characteristics of the past few decades fall within the range of natural variability experienced over prior centuries, there is no compelling reason to ascribe any portion of 20th-century climate change to the effects of anthropogenic CO2 emissions.

What was done
Based on analyses of tree-ring width data and their connection to large-scale atmospheric circulation, Touchan et al. developed summer (May-August) precipitation reconstructions for several parts of the eastern Mediterranean region (Turkey, Syria, Lebanon, Cyprus and Greece) that extend back in time anywhere from 115 to 600 years.

What was learned
Over the past six centuries, May-August precipitation varied on multiannual and decadal timescales, but on the whole there were no long-term trends.  The longest dry period occurred in the late 16th century (1591-1595), while there were two extreme wet periods: 1601-1605 and 1751-1755.  In addition, both extreme wet and dry precipitation events were found to be more variable over the intervals 1520-1590, 1650-1670 and 1850-1930.

What it means
The results of this study demonstrate there was nothing unusual or unprecedented about 20th-century precipitation events in the eastern Mediterranean that would suggest a CO2-induced influence.  If anything, as the eastern Mediterranean warmed while it transited from the Little Ice Age to the Current Warm Period, May-August precipitation actually become less variable, in contrast to the climate-alarmist claim that weather phenomena become more variable in the face of rising temperatures.