How does rising atmospheric CO2 affect marine organisms?

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Miocene Climate and CO2
Pagani, M., Authur, M.A. and Freeman, K.H. 1999. Miocene evolution of atmospheric carbon dioxide. Paleoceanography 14: 273-292.

What was done
Working with sediment cores from three deep sea drilling sites, the authors reconstructed a history of atmospheric CO2 concentration over the period stretching from 9 to 25 million years ago.

What was learned
During the early to late Miocene (25 to 9 million years ago), atmospheric CO2 concentration was similar to levels characteristic of Pleistocene glacial/interglacial intervals, i.e., 180 to 290 ppm.

What it means
At the height of the Miocene climatic optimum some 17 million years ago, deep water and high-latitude surface water temperatures were as much as 6C warmer than they are today, and it has long been generally believed that elevated atmospheric CO2 was responsible for the great warmth of that period. The authors' finding that the atmospheric CO2 concentration was "uniformly low" throughout the Miocene, however, leads them to state that what they found "appears in conflict with greenhouse theories of climate change." They also state that "there is no evidence for a sharp decline in [atmospheric] CO2 associated with EAIS [East Antarctic Ice Sheet] expansion" during the Miocene. In fact, they note that "atmospheric carbon dioxide rises [our italics] following the expansion of EAIS," which is also in conflict with greenhouse theories of climate change. And when theories conflict with reality ... do we really need to say that reality always wins?

Reviewed 15 June 1999