Investigations of variations of solar and climatic processes, and also researches of the evolution of the atmosphere, biosphere, and lithosphere raise problems of seeking the sources of cyclical processes. The problems of cyclicity exist in all space-time scales available to science - from the micro-world to the Universe, from minimal parts of second to tens of billions of years (Berry, 1992).

Internal and External Points of View

Two opposed approaches are being pursued in parallel. The main range of problems here is linked with interaction of internal (endogenous) and external (exogenous) components of the observed processes. In accordance with exogenous viewpoint, the causes of the Earth’s and the Sun’s cyclicity are associated with external sources located outside terrestrial and solar bodies. From the endogenous point of view cyclical and other processes are a direct consequence of the actual development of the Earth or the Sun which have their own auto-oscillatory and intrinsic frequencies. The endogenous models of the solar and terrestrial processes are being predominantly investigated by scientists and are backed by a well-developed theories.

For example, mainly internal global physico-chemical climate models help to understand the depth of the problem of the climate prediction. They are becoming more and more intricate and costly in term of human and computer resources (Moor III, 1996), but their prognostic value is increasing only gradually (Huebert, 1999). The internal models of the solar processes explain 11-year cyclicity by generation and regeneration of magnetic fields with specific movement of solar substance (Babcock, 1961, Leighton, 1969). These solar models have a limited forecast value likewise internal climate models, due to the limitation of measurable data and the absence of links with external sources of stable oscillations. The solar and terrestrial internal models are very useful for investigating physico-chemical processes and relationships among principal components of complicated bodily processes.

Main external models of the climate are related with solar-terrestrial physics. The effects of solar variability on the surface environment were recently referred by Reid (1999), Lean and Rind (1999). The total irradiance is known to vary at the level of 0.1% on the time scales up to that of the 11-year solar activity cycle (White et al.,1997, Pap and Frohlich, 1999). Variations in the range of 0.5-1,0% on 100-year time scales would be sufficient to explain the whole global climate variability of the last several centuries (Eddy, 1976, Bottomley et al., 1990, Reid, 1997). The second category of solar variability involves variations in spectral irradiance. The albedos of clouds, the ocean and land surfaces are wavelength dependent, but little is known about spectral irradiance variability. The third aspect of solar variability is that of the solar wind, which modulates both the flux of galactic cosmic rays to the Earth atmosphere and the strength of the global electric field. There is supposedly a relationship between cloud cover over certain areas of the Earth and variations of cosmic ray and electric field for a period of about one and a half 11-year cycles. The major advance in recent years has been the acceptance of solar variability as at least a potential cause of change in our environment (Reid, 1999).

The external barycentric model of the solar processes is based on calculated functions of the Sun’s movement about the centre of the gravity of the solar system (barycenter), such functions as changes in the orbital angular momentum, as changes in the acceleration components. The power spectra of these functions have periods which are, with the exception of 11, 22 and 89-year periods, very close to that of double and triple conjunctions of planets and Wolf number’s variations (Khlystov at al. 1992). This model or similar ones would be a very good base for climate predictions if the spectral characteristics of the Sun and the Earth were known, but it is not clear now how external periodic actions are transformed in solar and terrestrial processes. That is why solar and climate periods, since they have not coincided exactly with the spectra of the barycenter movement, should be directly investigated for the creation of the long-term forecast of the changes in the solar activity and climate.

It should be noted that the division of our interrelated world into internal and external fields has its own merits and drawbacks. In the search for the causes of the regular variations of heliogeophysical processes the shortcomings of such division are beginning to predominate. The Earth and the Sun are open systems, included in the resonant solar system, in which forced, intrinsic and auto-oscillatory processes are synchronized and have a complex genesis.

For example, we have had a very bright illustration of the influence of the auto-oscillatory process with the periods about 100 ka on the climate system in the Pleistocene - Holocene Epochs. The turning point of forming the oscillatory cell happened when the Arctic ocean was covered by pack ice (0.7Ma BP) and the heat of the Gulf Stream was isolated from arctic air. After that time, the long glacier (~90 ka), with ice sheets (60-75 Mkm³) on all northern continents, and short interglacial (~10ka) periods, which coincide with orbital cycles of the Earth, have determined changes in permafrost, geomorphology, tectonics and geodynamics (Berry, B.L., 1998a,b).

Variations and Prediction Models.

Natural climate variations of natural processes are the sum of systematic (periodic/aperiodic) and random components.

Systematic components may be represented either with the aid of physical-chemical sub-models (simple numerical, global circulation, and other models), if the mechanisms of their origin have been identified, or with the aid of physical-empirical models, if the mechanisms have not been conclusively established. Physical-empirical models use series of proxy and instrumental climate indicators and their approximations by different functions, for example, harmonic ones. The main causes for the appearance of harmonic climate components (oscillations) are the tidal (I_t ) and momentum (M_rev ) interactions of the celestial bodies in the solar system, which revolve on approximately circular orbits around the Sun. Only the planets of Mars and Pluto don’t really participate in forming cycles of solar system because they have small parameters I_t and M_rev simultaneously (Table).

Table. Relative planetary data, tidal interactions (It) of planets and the Sun, and their moments of revolving momentum (Mrev):

Random components (fluctuations) are the difference between a natural process and the sum of its systematic parts. The principal reason for the presence of random anomalies relates to short-term interactions of the bodies of the solar system with the comets and stars of the jet galactic streams and also to the natural random fluctuations in solar and terrestrial processes (Berry, 1992, 1998b).

The prognostic climate models for the time intervals from one year to several millions years should include all main processes of the Sun system, the Sun, and the Earth in corresponding time scales. For the time intervals of more than one million years it is necessary to take into account the processes connected with solar system movement around the central disk of our Galaxy (Berry, 1992).

Reliable predictions of future changes require the creation of physico-empirical climate models, which have the physical sense and could be provided with empirical data, and which will prove effective in simulating long-term past changes that can be reconstructed using different proxy climate indicators such as, for example, tree ring widths. The models can incorporate internal and external physico-chemical sub-models of different parts of the processes involved.

Acknowledgments

I thank A. V. Brouchkov, D. Sc., the Editor of Journal of Geocryology, for his suggestion to create the ADP&P and his excellent support.

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