How does rising atmospheric CO2 affect marine organisms?

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A Thousand-Year History of Chesapeake Bay Climate
Brush, G.S.  2001.  Natural and anthropogenic changes in Chesapeake Bay during the last 1000 years.  Human and Ecological Risk Assessment 7: 1283-1296.

What was done
The author analyzed sediment cores obtained from tributaries, marshes and the main stem of Chesapeake Bay for paleoecological indicators of regional climate change and land use variations over the past millennium.

What was learned
In the words of the author, "the Medieval Climatic Anomaly and the Little Ice Age are recorded in Chesapeake sediments by terrestrial indicators of dry conditions for 200 years, beginning about 1000 years ago, followed by increases in wet indicators from about 800 to 400 years ago."  This Medieval Climatic Anomaly is what most people refer to as the Medieval Warm Period, which Brush says is "recognized in many parts of the world from historical and paleocological evidence."

What it means
The findings of this paper represent just one more example of the reality and uniqueness of both the Medieval Warm Period and the Little Ice Age, which are the two preeminent climatic anomalies of the past thousand years.  The significance of these observations resides in the fact that the earth cycles back and forth between warm and cool periods (of which these named intervals are typical) on a millennial timescale, which suggests there is nothing unusual about the global warming of the past century or so, as it represents but the planet's natural recovery from the global chill of the Little Ice Age and the start of its return to Medieval Warm Period-like conditions.

Reviewed 16 January 2002