Wilhelm, B., Arnaud, F., Sabatier, P., Crouzet, C., Brisset, E., Chaumillon, E., Disnar, J.-R., Guiter, F., Malet, E., Reyss, J.-L., Tachikawa, K., Bard, E. and Delannoy, J.-J. 2012. 1400 years of extreme precipitation patterns over the Mediterranean French Alps and possible forcing mechanisms. Quaternary Research 78: 1-12.
The authors write that "mountain-river floods triggered by extreme precipitation events can cause substantial human and economic losses (Gaume et al., 2009)," and they say that "global warming is expected to lead to an increase in the frequency and/or intensity of such events," citing the IPCC (2007), "especially in the Mediterranean region (Giorgi and Lionello, 2008)."
What was done
Working at Lake Allos (44°14'N, 6°42'35" E) - a 1-km-long by 700-m-wide high-altitude lake in the French Alps - Wilhelm et al. carried out a coupled bathymetric and seismic survey of the lake's sediment infill, analyzing three sediment cores for grain size, geochemical composition, total organic carbon content, and pollen content and identity; while small-size vegetal macro-remains (pine needles, buds, twigs and leaves) were sampled at the base of the flood deposits and used for AMS 14C analysis, which was conducted at France's LMC14 carbon-dating laboratory. And although acknowledging the complicating fact that "changes in vegetation and/or land-use can modify soil stability/erodibility," they report that "the size of the coarsest sediment fraction still reflects stream flow velocity," citing Beierle et al. (2002) and Francus et al. (2002).
What was learned
The thirteen French scientists report that some 160 graded layers of sedimentary deposits over the last 1400 years were compared with records of historic floods; and they indicate that these comparisons "support the interpretation of flood deposits and suggest that most recorded flood events are the result of intense meso-scale precipitation events." And they make a point of noting that the temporal history of these deposits reveals "a low flood frequency during the Medieval Warm Period and more frequent and more intense events during the Little Ice Age."
What it means
Once again, we have another example of climate-alarmist (IPCC) contentions widely missing the mark when it comes to predicting which temperature extreme - hot or cold - produces both more frequent and more intense precipitation events, as well as the flooding that accompanies them.
Beierle, B.D., Lamoureux, S.F., Cockburn, J.M.H. and Spooner, I. 2002. A new method for visualizing sediment particle size distributions. Journal of Paleolimnology 27: 279-283.
Francus, P., Bradley, R.S., Abbott, M.B., Patridge, W. and Keimig, F. 2002. Paleoclimate studies of minerogenic sediments using annually resolved textural parameters. Geophysical Research Letters 29: 10.1029/2002GL015082.
Gaume, E., Bain, V., Bernardara, P., Newinger, O., Barbuc, M., Bateman, A., Blaskovicova, L., Bloschl, G., Borga, M., Dumitrescu, A., Daliakopoulos, I., Garcia, J., Irimescu, A., Kohnova, S., Koutroulis, A., Marchi, L., Matreata, S., Medina, V., Preciso, E., Sempere-Torres, D., Stancalie, G., Szolgay, J., Tsanis, I., Velasco, D. and Viglione, A. 2009. A compilation of data on European flash floods. Journal of Hydrology 367: 70-78.
Giorgi, F. and Lionello, P. 2008. Climate change projections for the Mediterranean region. Global and Planetary Change 63: 90-104.
IPCC. 2007. Climate Change 2007: The Physical Science Basis. Solomon, S., Qin, D., Manniing, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.), Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom.Reviewed 12 December 2012