How does rising atmospheric CO2 affect marine organisms?

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A Holocene Sediment Record from Northeast Greenland
Wagner, B., Bennike, O., Bos, J.A.A., Cremer, H., Lotter, A.F. and Melles, M. 2008. A multidisciplinary study of Holocene sediment records from Hjort So on Store Koldewey, Northeast Greenland. Journal of Paleolimnology 39: 381-398.

What was done
Working on a floating platform in the middle of a small lake (Hjort So) on an 80-km-long by 10.5-km-wide island (Store Koldewey) just off the coast of Northeast Greenland at 7555' to 7645'N and 1827' to 1910'W, the authors recovered two sediment cores of 70 and 252 cm length, the incremental portions of which they analyzed for grain-size distribution, macrofossils, pollen, diatoms, total carbon, total organic carbon, and several other parameters, the sequences of which were dated by accelerator mass spectrometry, with radiocarbon ages translated into calendar years before present.

What was learned
Wagner et al. report that their data reveal an "increase of the productivity-indicating proxies around 1,500-1,000 cal year BP, corresponding with the medieval warming," but that "after the medieval warming, renewed cooling is reflected in decreasing amounts of total organic carbon, total diatom abundance, and other organisms, and a higher abundance of oligotrophic to meso-oligotrophic diatom taxa." As they describe it, "this period, the Little Ice Age, was the culmination of cool conditions during the Holocene [our italics] and is documented in many other records from East and Northeast Greenland, before the onset of the recent warming [that] started ca. 150 years ago."

What it means
In addition to the obvious importance of their finding evidence for the Medieval Warm Period -- the existence of which climate alarmists are reluctant to acknowledge -- the six researchers' statement that the Little Ice Age was the culmination, or most extreme sub-set, of cool conditions during the Holocene, suggests that it would not be at all unusual for such a descent into extreme coolness to be followed by some extreme warming, which further suggests there is nothing unusual about the degree of subsequent warming experienced over the 20th century, especially in light of the fact that the ever-growing repository of data contained in our Medieval Warm Period Project indicates that the earth has not yet achieved the degree of warmth that held sway over most of the planet throughout large portions of that prior high-temperature period.

Reviewed 4 June 2008