How does rising atmospheric CO2 affect marine organisms?

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A Climate History of the Northwestern Mediterranean Region
Pla, S. and Catalan, J. 2005. Chrysophyte cysts from lake sediments reveal the submillennial winter/spring climate variability in the northwestern Mediterranean region throughout the Holocene. Climate Dynamics 24: 263-278.

What was done
Chrysophytes are a diverse group of primarily freshwater algae with over 1,000 known species that dominate phytoplankton assemblages of temperate and cold oligotrophic lakes. A key feature of chrysophytes is their production of resting siliceous cysts, which preserve a record of the dynamics of lake algal populations that can be further analyzed for paleoclimate signals. In the present study, the authors analyzed chrysophyte cyst data collected from 105 lakes in the Central and Eastern Pyrenees of northeast Spain to produce a history of winter/spring temperatures in this region throughout the Holocene.

What was learned
A significant oscillation was evident in the winter/spring temperature reconstruction in which the region's climate alternated between warm and cold phases over the past several thousand years. Of particular note were the Little Ice Age, Medieval Warm Period, Dark Ages Cold Period and Roman Warm Period, the warmest of which intervals was the Medieval Warm Period, which started around 900 AD and was about 0.25C warmer than it is currently. Following the Medieval Warm Period, temperatures fell to their lowest values of the entire record (about 1.0C below present), whereupon they began to warm, but remained below present-day values until the early 19th and 20th centuries, with one exception. A significant warming was observed between 1350 and 1400, when temperatures rose a full degree Celsius to a value about 0.15C warmer than the present, during what we refer to as the Little Medieval Warm Period.

Further examination of the authors' data reveals that the Modern Warm Period is not yet (and may never be) as warm as the Medieval Warm Period, for modern temperatures peaked in the 1970s-80s and declined throughout the 1990s.

What it means
In a regional contradiction of the strident claims of the world's climate alarmists, the results of this study suggest that winter and spring temperatures around the northwestern Mediterranean during the past two decades were no where near being unprecedented over the past two thousand years.

Reviewed 27 July 2005