How does rising atmospheric CO2 affect marine organisms?

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Temperature Histories of Remote Mountain Lakes in Europe
Battarbee, R.W., Grytnes, J.-A., Thompson, R., Appleby, P.G., Catalan, J., Korhola, A., Birks, H.J.B., Heegaard, E. and Lami, A.  2002.  Comparing palaeolimnological and instrumental evidence of climate change for remote mountain lakes over the last 200 years.  Journal of Paleolimnology 28: 161-179.

What was done
The authors report the results of a number of individual studies that employed a variety of palaeolimnological techniques for reconstructing the temperature histories of seven remote mountain lakes in Europe over the last 200 years.  The lakes studied were Ovre Neadalsvatn (Norway), Saanajarvi (Finland), Gossenkollesee (Austria), Hagelseewli (Switzerland), Jezero v Ledvici (Slovenia), Estany Redo (Spain, Pyrenees), and Nizne Terianske Pleso (Slovakia), which were chosen so as to be "as free from disturbance by human activity as possible."  Specifically, they were all above the local timber line, their catchments were free from obvious recreational or other human use, and most were far from atmospherically transported pollutants.

What was learned
During the nineteenth century, the seven sites experienced either general cooling or no trend in temperature.  During the twentieth century, on the other hand, the authors report that "all sites show a warming trend during the first few decades of the century," which peaks between 1930 and 1950.  Thereafter, all of the sites again depict cooling, as well as a steep warming over the last ten to twenty years of the record.  However, for only two of the seven sites does the final warming lead to warmer temperatures than those of the 1930s and 40s.  Of the remaining five sites, three of them end up being cooler than they were prior to mid-century, while two of them end up exhibiting about the same temperature.

What it means
Much like the U.S. Historical Climatology Network database (see our Temperature Record of the Week feature), these temperature reconstructions derived from limnological data from pristine mountain lakes in Europe support the tenet of our Editorial of 1 July 2000, i.e., that "there has been no global warming for the past 70 years," in that it is no warmer now in these locations than it was in the 1930s and 40s.

Reviewed 29 January 2003