How does rising atmospheric CO2 affect marine organisms?

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The Medieval Warm Period and Little Ice Age in New Zealand
Williams, P.W., King, D.N.T., Zhao, J.-X. and Collerson, K.D. 2004. Speleothem master chronologies: combined Holocene 18O and 13C records from the North Island of New Zealand and their palaeoenvironmental interpretation. The Holocene 14: 194-208.

What was done
The authors say their paper "revises and builds on results presented ? by Williams et al. (1999) on stable isotope stratigraphy from caves at Waitomo," which is located at 38.3S latitude about 35 km from the west coast of the central North Island of New Zealand. Specifically, they enhanced three existing speleothem records "by adding another chronology, increasing the subsample resolution of existing records, and by much improving the temporal control of all chronologies by basing it entirely on uranium series TIMS dating."

What was learned
Williams et al.'s speleothem master chronologies reveal a warmer-than-present "late-Holocene warm peak" between 0.9 and 0.6 ka BP that they equate with the Medieval Warm Period in Europe. In New Zealand, they note that this period "coincided with a period of Polynesian settlement (McGlone and Wilmshurst, 1999)." Thereafter, they report that temperatures "cooled rapidly to a trough about 325 years ago," which they say "was the culmination of the 'Little Ice Age' in Europe."

What it means
In clear contradiction of the claims of climate alarmists, these findings are but another example of the unending stream of studies from all around the world that continue to document the global presence of a warmer-than-present Medieval Warm Period. We continue to highlight these facts, which are becoming ever more difficult to deny, because they demonstrate that the Medieval Warm Period was warmer than the Modern Warm Period, even though the air's CO2 concentration of that earlier period was 100 ppm less than it is currently. This being the case, there is absolutely no reason to attribute our current warmth to our current elevated atmospheric CO2 content, as there is an historical precedent for even higher temperatures than those of the present with much lower-than-current atmospheric CO2 concentrations.

McGlone, M.S. and Wilmshurst, J.M. 1999. Dating initial Maori environmental impact in New Zealand. Quaternary International 59: 5-16.

Williams, P.W., Marshall, A., Ford, D.C. and Jenkinson, A.N. 1999. Palaeoclimatic interpretation of stable isotope data from Holocene speleothems of the Waitomo district, North Island, New Zealand. The Holocene 9: 649-657.

Reviewed 5 May 2004