Climate of the Earth - how we can characterize it: are we witnesses of global warming or, on the contrary, is it getting cooler and our descendants will face a new glacial period?* Is warming in one hemisphere accompanied by climatic cooling in the other? Palaeoclimatologists and geophysicists, paleontologists and mathematicians are trying to find answers to these questions. It is no wonder that in the mid-2005 Nauka v Sibiri (Science in Siberia) newspaper published two materials devoted to climatic changes that took place on our planet in the past. Iosif Smulsky, Dr. Sc. (Phys.& Maths.), described attempts to estimate changes in the volume of solar heat descending on different zones of the Earth's surface using mathematical methods. He believes it is necessary to solve two problems to find the answer: first, scientists have to estimate orbital shape changes caused by interactions with other planets of the solar system; second, they have to calculate changes of the Earth's axial tilt against the plane of its orbit.

Interconnection of these astronomical characteristics with climatic changes was satisfactorily proved by Yugoslav mathematician and astronomer Milutin Milankovic. But in that time calculations of the Earth's orbit shape and its axis tilt angle were carried out using an approximate analytical method: that is why climatic models of past epochs, constructed on the basis of extrapolations were rather approximate. Using a modern supercomputer MVS-1000 of the Novosibirsk Computer Center (RAS Siberian Branch), Iosif Smulsky defined the shapes of all planets of the solar system for every year for the last 100 mn years; one should bear in mind that his calculation errors were thousands times less than that of his precursors who had tried to solve the same problem. In the long term he plans to carry out calculations for the whole history of the Earth, i.e. for a period of 5 bn years.

As for the problem of evolution of the Earth's axial tilt, its solution is far from being completed, because the results of Herculean calculations are rather poor. Having compared his own calculations with that of other scientists engaged in research works on the Earth's climate, Smulsky came to the conclusion: in the next 10 thous. years the climate of the Northern hemisphere would become cooler.

At the same time the author acknowledges: apart from the astronomical factors under study, there is a great number of other things influencing climatic changes. But all of them are of catastrophic nature (fall of an asteroid, its absorption by the Sun, influence of another planetary system, etc.) and cannot be analyzed by purely scientific methods. If it turns out that astronomic factors under study have negligibly small influence on the climate of the Earth, even in this case, Smulsky believes, there will be less uncertainty in defining reasons of climatic changes.

Article of Yuri Karogodin, Dr. Sc. (Geol. & Mineral.) is devoted to another aspect of the problem of climatic changes that had taken place in the past and their modeling in the long run. The most significant cycles (180 - 200 mn years of duration) and periodic fluctuations of the Ocean level (hundreds of meters) are interdependent, states the author. And up and down movements of the Ocean level, periods of maximum warming and cooling are mirrored in sediments. Many age-long climatic data interpreted by geologists allow to forecast future climatic changes. But the author refers to a long-term forecast only: he believes that maximum warming and maximum Ocean level will arrive in 45 - 50 mn years.

Such long-term forecasts are of scientific interest only. But we realize that the results of studies of the most significant climatic cycles have practical application. Changes of the Ocean level and of the climate result in strong changes in the organic world that are used for drawing border lines between many geological systems. And all data on geological chronology are closely related with geological explorations, mineral explorations, etc, i.e., interrelation of scientific studies and real life is not direct, but obvious.

Study of shorter cycles is targeted at solving one more problem of geology and environmental science. At the present moment countries of the whole world are exploring the reserves of gas hydrates - compounds consisting of methane and, sometimes, hydrogen sulphide and water which form snow-like masses in near-bottom areas. According to the latest estimates, reserves of methane in these masses are some ten times greater than that in traditional deposits.

Lowering of the Ocean level and climate warming shall inevitably cause melting of gas hydrates and release of natural gas into sea water and atmospheric air. Scientists can approximately estimate economic results of the depletion of natural fuel, but global changes of ecological situation due to increased concentrations of methane and hydrogen sulphide in the atmospheric air are not predictable.

So, shall we face a significant warming in future? Karogodin says that the problem is too difficult, and only combined efforts of scientists of different areas can help find the right answer and develop a program which can prevent the consequences of ecological disaster. The author believes that this problem can only be solved by the RAS jointly with other national scientific institutions.

Nauka v Sibiri, (Science in Siberia), No. 26, 2005

Prepared by Andrey BIRYUKOV

* See: Yu. Izrael, "Threat of Climatic Catastrophe?", Science in Russia, No. 4, 2004. - Ed.

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