On the Solar Shape and Some Consequences or Towards “Helioclimatology”

Solar radiation varies at different time scales, as a consequence of solar activity. The energy received from the Sun on our atmosphere is one of the natural drivers. Since this energy is not constant, it has been postulated that our climate may response to any irradiance variations. Although differences in the amplitude of centennial temperature variability have been widely discussed in the literature, the picture with relatively small variability is arguably best known by a wider audience. But how subtle variations of solar radiation are produced? Despite all the efforts, climate and weather still remains an unsolved puzzle. To try to go further, an element that has been investigated is the similarity of periodicities between several solar activity indices and different meteorological/climatic parameters. The literature contains a long history of “pseudo” correlations (positive or negative) between weather and climate parameters like temperature, rainfall, droughts, etc. and, solar activity cycles like the 27-day one, those of 11-years, 22-years, 80–90 years or even longer. An indisputable physical mechanism, is through the so-called “asphericity-luminosity parameter w”, which might act to produce these relationships. In this review paper we will first show how the solar shape may influence the irradiance (an attempt to answer to the above-mentioned question), and then, we will progress on the way the different cycles can be analyzed in the scope of determining solar influences on terrestrial climate. We denote these causal relationships by the term “helioclimatology ” and we will conclude by emphazing the need of new dedicated satellites such as SDO or DynaMICS