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Solar-Climate Links Discerned From Tree-Ring Periodicities in Brazil and Chile
Nordemann, D.J.R., Rigozo, N.R. and de Faria, H.H. 2005. Solar activity and El-Niņo signals observed in Brazil and Chile tree ring records. Advances in Space Research 35: 891-896.

What was done
Tree rings from species sensitive to fluctuations in temperature and precipitation from the southern region of Brazil and Chile were studied along with sunspot data via harmonic spectral and wavelet analysis in an effort to obtain a greater understanding of the effects of solar activity, climate and geophysical phenomena on the continent of South America, where the time interval covered by the tree-ring samples from Brazil was 200 years and that from Chile was 2500 years.

What was learned
Spectral analysis revealed periodicities in the tree rings that corresponded well with the DeVries-Suess (~200 yr), Gleissberg (~80 yr), Hale (~22 yr), and Schwabe (~11 yr) solar activity cycles; while wavelet cross spectrum analysis of sunspot number and tree-ring growth revealed a clear relation between the tree-ring and solar series.

What it means
Why have we chosen to highlight this particular study? We have done so simply because it is typical of a vast array of studies that have come to essentially the same conclusion, i.e., that cyclical solar-activity oscillations of many periodicities have always influenced earth's climate and always will. These studies are truly legion; and the veracity of their findings cannot be denied (see Solar Effects, for example, in our Subject Index). What is more, Braun et al. (2005) have demonstrated that the superposition of the DeVries-Suess and Gleissberg solar cycles could have resulted in climatic variability that repeats with a 1,470-year period, which phenomenon could well be what produced the Roman Warm Period, Dark Ages Cold Period, Medieval Warm Period, Little Ice Age and, most recently, the Modern Warm Period.

Braun, H., Christl, M., Rahmstorf, S., Ganopolski, A., Mangini, A., Kubatzki, C., Roth, K. and Kromer, B. 2005. Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model. Nature 438: 208-211.

Reviewed 12 April 2006