6. Conclusion

[65]  The analysis carried out shows that the neglecting of orbital theory history resulted in significant delay of its further development. This conclusion is supported by paper by Crucifix et al. [2006]: "The climate response to the astronomical forcing''. The summary of the paper says: "Links between climate and Earth's orbit have been proposed for about 160 years. Two decisive advances towards an astronomical theory of palaeoclimates were Milankovitch's theory of insolation (1941) and independent findings, in 1976, of a double precession frequency peak in marine sediment data and from celestial mecanics calculations. It is recognized today that climatic interections at the global scale were involved in the processes of glacial inception and deglaciation''.

[66]  The extract above has some important inaccuracies. Firstly, the significant role of J. Croll in orbital theory development is not mentioned among the "decisive advances''. However, the quotation given verifies the fact that Croll's discovery of feedbacks is an outstanding achievement of theoretical paleoclimatology far ahead its time. From this extract is evident that the influence of feedbacks between different components of climatic system and orbitally-caused insolation variations that Croll stated more than 130 years ago has been only "recognized today''. Perhaps that is the reason why Croll's name isn't mentioned in paper [Crucifix et al., 2006]? After all, if we do not consider feedbacks, it would turn out that after Croll and Milankovitch there were few outstanding achievements in theoretical paleoclimatology. In this paper [Crucifix et al., 2006] Milankovitch theory is referred to not as theory of climate oscillations like Milankovitch termed it and not as paleoclimate theory like it is often spoken of, but as "insolation theory''. I guess it may suggest the authors' [Crucifix et al., 2006] public acceptance of drawbacks of the paleoclimatic part of Milankovitch theory.

[67]  One can not also agree with the statement that one of the "decisive advances towards an astronomical theory'' is the detection of double precession peak. Certainly, Hays et al., [1976] study turned to be the strongest argument for the orbital hypothesis. However, its main result is not the detection of double precession peak (that by the way contributes the least to climatic oscillations), but the detection of 1) all the three orbital periods in paleoclimatic records and 2) phase compliance between variations of orbital elements and attributed components of paleoclimatic record. It worth mentioning that precession period in sedimentation records have been found earlier (see, for example, [Bradley, 1929]). However it didn't become the decisive evidence of orbital hypothesis. Furthermore, the Milankovitch theory was rejected by majority of scientists in the mid-20th century [Imbrie and Imbrie, 1986; Schwarzbach, 1950].

[68]  The concluding section of paper [Crucifix et al., 2006] titled "The Future of Palaeoclimate Modelling'' mentions again the need for the account of global climatic interactions in development of paleoclimate astronomical models. Of course, this is a correct conclusion. I would only add that the work will be done in vain if the input signal in development of such models is again monthly or diurnal insolation at single latitude.

[69]  The history development of the paleoclimate orbital theory and contemporary empirical data analysis made it possible to suggest a qualitative pattern for global climatic changes characterized by orbital periodicities for the entire Phanerozoic. Our views are based on a single system of ideas and are no contradictive. The construction of mathematically strict paleoclimatic model corresponding to these views is a very hard task. However, such a way to study the global climatic oscillations mechanisms of the past seems to be the only logic and successive. The main conclusions of our research are the following:

[70]  1. The insolational forcing expressed by the variations of monthly insolation at a single latitude shouldn't be used for paleoclimate modeling and interpretation as such input signal (i.e. June or July insolation at 65oN) doesn't fully account for the solar radiation change actually forcing the Earth's climate. Since the input signal is not valid there is not possibility to correctly define the mechanism of insolation variations transformations into the global climatic changes even if the output signal (indirect paleoclimatic records) is reliable.

[71]  2. The construction of paleoclimatic model should be accounted for continuous in time (full annual) and space (for the entire Earth) insolation variations generated by change of all the three orbital elements. The solution of the problem should also be accounted for different Earth feedbacks.

[72]  3. The main problem of orbital theory development is the elaboration of individual feedback mechanisms, enhancing the effect of every orbital element insolation signals. The forcing of feedback mechanisms on orbital signals depends on global paleoclimatic state of the Earth, i.e. can change within the geological time scales.

[73]  4. The search of individual feedbacks should be based on thorough study of diverse paleoclimatic records.


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