How does rising atmospheric CO2 affect marine organisms?

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Floods of the European Alps
Glur, L., Wirth, S.B., Buntgen, U., Gilli, A., Haug, G.H., Schar, C., Beer, J. and Anselmetti, F.S. 2013. Frequent floods in the European Alps coincide with cooler periods of the past 2500 years. Scientific Reports 3: 10.1038,srep02770.

The authors write that "severe floods triggered by intense precipitation are among the most destructive natural hazards in Alpine environments, frequently causing large financial and social damage," and they say that "potential enhanced flood occurrence due to global climate change would thus increase threats to settlements, infrastructure, and human lives in the affected regions." However, they note that, currently, "projections of intense precipitation exhibit major uncertainties" and that "robust reconstructions of Alpine floods are limited to the instrumental and historical period," giving one reason to question whether global warming would lead to such a consequence.

What was done
In a study designed to reduce these uncertainties and extend reconstructions back in time beyond the instrumental period, Glur et al. developed "a multi-archive Alpine flood reconstruction based on ten lacustrine sediment records, covering the past 2500 years." More specifically, they studied ten lakes situated north of the Central Alpine arc along a montane-to-Alpine transect, spanning an elevation gradient from 447 to 2068 m asl," which allowed "the extraction of a synoptic, rather than a merely local rainfall signal revealed by a single-lake study." And to verify their approach to the subject, they compared the last 500 years of their Central Alpine flood reconstruction with an independently established flood record for that period that was based on historical documents, as developed and described by Schmocker-Fackel and Naef (2010).

What was learned
"Regarding the best-characterized climatic periods during the past 2500 years," the eight researchers report that "flood activity was generally enhanced during the Little Ice Age (1430-1850 C.E.; LIA) compared to the Medieval Climate Anomaly (950-1250 C.E.; MCA)." And they say that "this result is confirmed by other studies documenting an increased (decreased) flood activity during the LIA (MCA) in the Alps," citing the studies of Schmocker-Fackel and Naef (2010), Czymzik et al. (2010), Wilhelm et al. (2012) and Swierczynski et al. (2012).

What it means
For the European Alps, there would appear to be good reason to believe that any further warming of the globe would not lead to flood-induced "increased threats to settlements, infrastructure, and human lives," for real-world data suggest that it is cooling that leads to such consequences in that part of the world.

Czymzik, M., Dulski, P., Plessen, B., von Grafinstein, U., Naumenn, R. and Brauer, A. 2010. A 450 year record of spring-summer flood layers in annually laminated sediments from Lake Ammersee (southern Germany). Water Resources Research 46: 10.1029/2009WR008360.

Schmocker-Fackel, P. and Naef, F. 2010. Changes in flood frequencies in Switzerland since 1500. Hydrology and Earth System Sciences 14: 1581-1594.

Swierczynski, T., Brauer, A., Lauterbach, S., Martin-Puertas, C., Dulski, P., von Grafenstein, U. and Rohr, C. 2012. A 1600 yr seasonally resolved record of decadal-scale flood variability from the Austrian Pre-Alps. Geology 40: 1047-1050.

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.

Reviewed 5 March 2014