Last updated: 11.24.2005.


Sun, Climate and Their Changes in Time

Boris Komitov


            In this paper an comparison between the solar activity variations  and   climate changes has been provided.  The used solar activity reconstructions are on the base of almost all main, famous nowadays data series: a) instrumental observations  of sunspot activity during the last ~ 400 years; b) ground based and  satellite observations of  solar EUV , radio and corpuscular fluxes  , solar and interplanetary magnetic field, solar wind  and total solar irradiance for the last  few decades; c) historical records for auroras and simple eye observations of sunspots (for the last 1700 years); d) “cosmogenic” radioisothopes ( 14C and 10Be) measurements in tree rings  (for the last 10 000 years), continental  ices ( the last 1200 years) and oceanic sediments probes (the last ~400 000 years) .            

Four time-scales of the climate changes has been used in this study: “geological” - for the last ~ 800 million years; “prehistorical  “ (1 and 2)- for the last ~130 000 years and ~23000 years respectively ; and “historical” scale – for the last 1200 years.  For the last three one the   relationship  ‘Sun-climate’ has been discussed.  The climatic changes in Bulgaria during the last century and its relation to the solar activity has been to shortly described.           

It is concluded that the Sun’s variability is the main factor of the climatic changes  during the last ~ 400 000 years . The  Earth orbit’s effects, described in Milankovich theory are significant too in “prehistorical scale-1”, but most probably, they are on the second place. All significant climatic extremums during the last 10 000 years are in coincidience with corresponding solar activity extremums. The “global warming” effect in 20th century corresponded with the most higher solar activity level during the last ~ 1000 years,  and no antropogenic effect for the explanation of this climatic phenomena  is  necessary to include .           

An evidence that the main historical tendencies are modulated  by climatic changes and solar-climatic relationships is given. The last one is discussed in the light of Arnold Toynbee’s “civillization  theory”.




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