Catastrophic Superstorms of the French Mediterranean Coast

With respect to extreme weather events, Dezileau et al. (2011) write that the major question of the day is: "are they linked to global warming or are they part of natural climate variability?" And in regard to the significance of this question, they say "it is essential to place such events in a broader context of time, and trace the history of climate changes over several centuries," because "these extreme events are inherently rare and therefore difficult to observe in the period of a human life."

Working with regional historical archives, plus sediment cores they extracted from two Gulf of Aigues-Mortes lagoons in the northwestern part of the occidental Mediterranean Sea that they analyzed for bio- and geo-indicators of past storm activities there, Dezileau et al. assessed "the frequency and intensity of these events during the last 1500 years," as well as "links between past climatic conditions and storm activities."

The nine researchers (all from France, and spread among seven different institutions) report they found evidence of four "catastrophic storms of category 3 intensity or more," which occurred at approximately AD 455, 1742, 1848 and 1893. And "taking into account text description of the 1742 storm," they conclude that it was "of category more than 4 in intensity," and that all four of the storms "can be called superstorms." In addition, they make a point of noting that "the apparent increase in intense storms around 250 years ago lasts to about AD 1900," whereupon "intense meteorological activity seems to return to a quiescent interval after (i.e. during the 20th century AD)." And they add that, "interestingly, the two periods of most frequent superstorm strikes in the Aigues-Mortes Gulf (AD 455 and 1700-1900) coincide with two of the coldest periods in Europe during the late Holocene (Bond cycle 1 and the latter half of the Little Ice Age.)"

Dezileau et al. suggest that "extreme storm events are associated with a large cooling of Europe," and they calculate that the risk of such storms occurring during that cold period "was higher than today by a factor of 10," noting that "if this regime came back today, the implications would be dramatic."