How does rising atmospheric CO2 affect marine organisms?

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Little Ice Age Glaciation in Greenland During the Holocene
Reference
Kelly, M.A., Lowell, T.V., Hall, B.L., Schaefer, J.M., Finkel, R.C., Goehring, B.M., Alley, R.B. and Denton, G.H. 2008. A 10Be chronology of lateglacial and Holocene mountain glaciation in the Scoresby Sund region, east Greenland: implications for seasonality during lateglacial time. Quaternary Science Reviews 27: 2273-2282.

What was done
Working in Greenland's Scoresby Sund region (~70-72N, 22-28W), which is the largest embayment on Greenland's east coast, the authors conducted "a coordinated, multi-year campaign of reconnaissance field mapping, radiocarbon dating of shells in raised marine features and cosmogenic-exposure dating of glacial features."

What was learned
Kelly et al. report that 38 new cosmogenic (10Be) exposure ages indicate that prominent moraines were deposited by mountain glaciers during the Little Ice Age, and that these glaciers "were more extensive than at any other time since the Early Holocene Epoch." In addition, citing Koch and Clague (2006), they state that this finding "is similar to many Northern Hemisphere mountain glacier records which show that maximum Holocene ice extents occurred during Late Holocene time," as is also suggested by several of the studies we have reviewed and archived under the general heading of Little Ice Age in our Subject Index.

What it means
The only point we wish to make about this finding is that it is not at all surprising that -- starting from the coldest point (the Little Ice Age, from which we have been recovering over the past century or so) of the current interglacial period (the Holocene, which itself just happens to be the coldest of at least the last five interglacial periods (Petit et al., 1999) -- the earth would warm somewhat, and perhaps even a whole lot, even if the air's CO2 concentration had never risen above 300 ppm, as it never did over the prior four interglacial periods, whose peak temperatures averaged about 2C more than the peak temperature of the mid-Holocene, which was also warmer than it is today.

References
Koch, J. and Clague, J.J. 2006. Are insolation and sunspot activity the primary drivers of global Holocene glacier fluctuations? PAGES Newsletter, p. 20-21.

Petit, J.R., Jouzel, J., Raynaud, D., Barkov, N.I., Barnola, J.-M., Basile, I., Bender, M., Chappellaz, J., Davis, M., Delaygue, G., Delmotte, M., Kotlyakov, V.M., Legrand, M., Lipenkov, V.Y., Lorius, C., Pepin, L., Ritz, C., Saltzman, E., and Stievenard, M. 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.

Reviewed 22 April 2009