Girardin, M-P., Tardif, J., Flannigan, M.D. and Bergeron, Y. 2004. Multicentury reconstruction of the Canadian Drought Code from eastern Canada and its relationship with paleoclimatic indices of atmospheric circulation. Climate Dynamics 23: 99-115.
What was done
The authors developed a 380-year reconstruction of the July monthly average of the Canadian Drought Code (CDC, a daily numerical rating of the average moisture content of deep soil organic layers in boreal conifer stands that is used to monitor forest fire danger) from 16 well replicated tree-ring chronologies from the Abitibi Plains of eastern Canada just below James Bay.
What was learned
Among other things, Girardin et al. report that "cross-continuous wavelet transformation analyses indicated coherency in the 8-16 and 17-32-year per cycle oscillation bands between the CDC reconstruction and the Pacific Decadal Oscillation prior to 1850," while "following 1850, the coherency shifted toward the North Atlantic Oscillation."
What it means
The authors say their results lead them to suggest that "the end of [the] 'Little Ice Age' over the Abitibi Plains sector corresponded to a decrease in the North Pacific decadal forcing around the 1850s," and that "this event could have been followed by an inhibition of the Arctic air outflow and an incursion of more humid air masses from the subtropical Atlantic climate sector." In this regard, they note that several paleo-climatoogical and paleo-ecological studies have suggested that "climate in eastern Canada started to change with the end of the 'Little Ice Age' (~1850)," citing the works of Tardif and Bergeron (1997, 1999), Bergeron (1998, 2000) and Bergeron et al. (2001), while further noting that Bergeron and Archambault (1993) and Hofgaard et al. (1999) have "speculated that the poleward retreat of the Arctic air mass starting at the end of the 'Little Ice Age' contributed to the incursion of moister air masses in eastern Canada."
This substantial group of reports clearly places the "beginning of the end" of the Little Ice Age in the Abitibi Plains of Canada fully half a century before what is suggested by the Mann et al. (1998, 1999) reconstruction of Northern Hemispheric temperature over the past millennium. Hence, it represents yet another set of studies that testifies against the validity of that faulty representation of earth's temperature history.
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Reviewed 24 November 2004