How does rising atmospheric CO2 affect marine organisms?

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The Ice Phenology of Lake Simcoe, Southern Ontario, Canada
Futter, M.N.  2003.  Patterns and trends in Southern Ontario lake ice phenology.  Environmental Monitoring and Assessment 88: 431-444.

What was done
The author analyzed data on ice break-up dates and length of ice-free season for several lakes in Southern Ontario, Canada.  However, only one lake had ice break-up dates extending back beyond 1910 (Lake Simcoe, to 1853), and only one had ice-free season data extending back beyond 1971 (Lake Simcoe, to 1853).  Hence, Lake Simcoe is the only lake that has sufficient data to determine, in the words of the author, "whether the trends in Lake Simcoe ice phenology were due to the end of the Little Ice Age, or to more recent warming."

What was learned
Breaking the Lake Simcoe data into three comparable time intervals (1853-1899, 1900-1949, 1950-1995), Futter determined that "only the period from 1853-1899 showed a statistically significant trend indicative of warming temperatures in both the ice break up and ice free season series."  In fact, he reports that the data from 1900-1949 indicate a cooling trend, and that the data from 1950-1995 "show slight but not statistically significant evidence of warming temperatures."

What it means
As we and many others have long contended, the so-called unprecedented warming of the 20th century was likely nothing more than the natural recovery of the world from the chilly conditions of the Little Ice Age.  This claim is well supported by the Lake Simcoe ice data, which only show evidence of significant warming over the period from 1853 to 1899.  Late 20th century warming, on the other hand (when greenhouse gas effects should have been most evident), was not statistically significant, which finding pretty much speaks for itself for this particular part of the world: the Little Ice Age was a significantly cooler period than that of the present, while the most recent boost to the Modern Warm Period (which may or may not have been due to greenhouse gas emissions) has amounted to very little and is, in fact, insignificant.

Reviewed 12 November 2003