How does rising atmospheric CO2 affect marine organisms?

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The Millennial-Scale Oscillation of Climate
Dokken, T., Andrews, J., Hemming, S., Stokes, C. and Jansen, E.  2003.  Researchers discuss abrupt climate change: Ice sheets and oceans in action.  EOS, Transactions, American Geophysical Union 84: 189, 193.

What was done
The authors report on discussions that took place at the first formal workshop (held in December 2002) of the Ice Sheet-Ocean Interaction working group that was recently set up within the International Marine Past Global Changes Study (IMAGES) program "to answer questions concerning Heinrich events through an active interchange of ideas and information among the fields of glaciology, glacial geology, sendimentology, geochemistry, and paleoceanography."

What was learned
A number of speculative ideas were discussed, along with potential research thrusts that could help to clarify concepts related to the subject of past climate change.  In their introduction to these more tentative concepts, however, the authors reiterate a number of well established facts that are worth repeating yet again.  First, "large temperature variations on land, in the air, and at the ocean surface, and highly variable flux of ice-rafted debris (IRD) delivered to the North Atlantic Ocean show that rapid climate fluctuations took place during the last glacial period."  Second, "these quasi-periodic, high-amplitude climate variations followed a sequence of events recognized as a rapid warming, followed by a phase of gradual cooling, and terminating with more rapid cooling and increased flux of IRD to the North Atlantic Ocean."  Third, each of these climatic oscillations, dubbed Dansgaard/Oechger (D/O) cycles "lasted 1500 years, and was followed by an almost identical sequence [where] approximately every fourth cycle culminated in a more pronounced cooling with a massive discharge of IRD into the North Atlantic Ocean [a Heinrich event that produces an ocean-bottom Heinrich layer of IRD] over an interval of 500 years."  Fourth, Heinrich events "seem to be part of an almost regular system; this suggests some external climate forcing."

What it means
If a regular, external forcing of climatic cycles of approximately 1500 years' duration existed throughout the past glacial period, one would expect it should also exist "today," meaning throughout the current interglacial or Holocene period; and it does, although in significantly subdued format [see Climate Oscillations (Millennial Variability) in our Subject Index].  Also, one would expect that such a regular, external forcing of climate would likely be solar-induced; and it appears that it is [see Solar Effects (Millennial-Scale Cycles) in our Subject Index].  Hence, it would appear that the Modern Warm Period -- which it can now be said we have entered upon -- is but the natural "next step" in the solar-induced sequence of millennial-scale climate change that has brought us the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age.

Reviewed 6 August 2003