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Contributions of solar variability and geophysical events in the climate of South America: study of the sun-climate relationships in growth rings of trees

Abstract

To better understand the relationship between the phenomena involved and extend the forecasts for a bigger time scale in the future, it is necessary to push back even further the timescale of analysis of the past. It is therefore necessary to study natural records that represent indicators of the variations in environmental, meteorological and climatic parameters, for example. Several natural phenomena contributed to the accumulation through time of isotopes, elements or compounds deposited in marine or lake sediments and in the ice of the polar icecaps and glaciers. The concentrations of material deposited represent natural records of the phenomena involved in their rate of formation and/or accumulation. The physical growth of trees also represents an indicator of various environmental parameters, such as air temperatures, pluviometry, presence of nutrients, etc. The trees thus present natural records of the variations in the environmental parameters most involved in their growth. When the trees show growth rings in the interior of their trunks and branches, the simple counting of these annual rings represents in a direct way the scale of time. The variation in the thickness of the growth rings of trees deserves to be investigated as a regional and/or global indicator of the climatic variability on the continents to the scale of one year to thousands of years. The following stage of this research is the search for the influence of solar variability, of volcanic activity and phenomena such as El Niño events, for the identification of characteristic periodicities and other correlations. In addition to this identification of characteristic periodicities, an analysis will be undertaken of the variations of respective amplitudes of these signals by the wavelet method. Thus we will be able to reconstitute the history of variations (activity and emission of energy) of the Sun in the past covered by the duration of the chronologies of the trees studied, that is, typically for the past, moving from the present to 2 thousand years back in time. (AU)

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