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Solar Activity Signals in Chilean Tree Growth Data
Rigozo, N.R., Nordemann, D.J.R., Silva, H.E., Souza Echer, M.P. and Echer, E. 2007. Solar and climate signal records in tree ring width from Chile (AD 1587-1994). Planetary and Space Science 55: 158-164.

What was done
The authors performed a complex Morlet wavelet analysis of tree-ring width data for the period AD 1587-1994, which were obtained by Rigozo et al. (2006) from native Chilean Pilgerodendrum cupressoide trees ranging from 300 to 450 years of age that grew in the Glacier Pio XI area of Chile (49°12'S, 74°55'W), which they compared via cross-wavelet analyses with solar activity (1610-1994), as represented by the Group Sunspot Number, and the El Niņo-Southern Oscillation phenomenon (1876-1994), as represented by the Southern Oscillation Index.

What was learned
Rigozo et al. discovered short-term periodicity on the order of 2-7 years in the tree-ring width data that they felt was "likely associated with ENSO effects." In addition, they report that "the 11-year solar cycle was present during the whole period," and that there were significant periods of 52 and 80-100 years that were "coincident with the fourth harmonic (52 years) of the Suess cycle (208 years) and Gleissberg (~80-100 years) solar cycles."

What it means
The five Brazilian scientists concluded that "the Group Sunspot Number signal near 11 and 80 years has a great influence [our italics] on tree ring index," that solar variability "was one of the main factors [our italics] influencing tree growth," and that the observed solar-induced growth impacts were likely driven by "solar modulation of local/regional climate." Hence, their work suggests that small but common and recurring variations in solar activity possess the ability to significantly alter earth's climate - its "rainfall and temperature," as they say - on a local/regional basis; and since variations in solar activity are experienced over the entire earth, the net result of all of the solar-induced local and regional impacts would likely be a modulation of the global climate, which further suggests that the ascending phase of an ever-so-subtle millennial-scale cycle of solar activity may well be sufficient to produce an increase in temperature comparable to what occurred during earth's transition from the depth of the Little Ice Age to the pinnacle of modern warmth.

Rigozo, N.R., Nordemann, D.J.R., Souza Echer, M.P., Echer, E., Silva, H.E. and Prestes, A. 2006. Solar and climate imprints in tree ring width time series from Chile (1587-1994 A.D.). Trend Appl. Sci. Res. 1: 73-78.

Reviewed 11 July 2007