As early as in the 19th century scientists discovered that carbon dioxide retains the heat from the sun in the atmosphere, affecting the Earth's surface temperature. With the beginning of the industrial revolution and scientific and technological progress the world consumption of various fuels grew, raising respectively the atmospheric carbon dioxide level.

Nevertheless for many years scientists didn't take this problem into consideration because it was common knowledge that excessive atmospheric CO2 sinks into the world's oceans. In 1957-1958, during the International Geophysical Year, scientists decided to check that assumption through a number of investigations on the peak of the Hawaii volcano Mauna Loa. The data from Mauna Loa show that the concentration of carbon dioxide rises evenly. [Source: Matthew Paterson, Global Warming and Global Politics, London and New York, 1996.]

In connection with the political instability in the world during the Cold War, up to the middle of the eighties, international cooperation in the reduction of greenhouse gas emissions was unfeasible. Measures for nature protection policy of most countries did not extend beyond the frameworks of the national level. However attitudes of states started changing due to huge efforts of scientists from many countries with regard to the ozone crisis when in 1987 in Montreal a Protocol on Restrictions was signed and finally follows with a ban on emissions from CFC production. The success of the Montreal Protocol has contributed to the prospects for international cooperation relating to other problems of global nature protection.

When one of outstanding climatologists of the United State James Hansen from NASA declared to the Congress in 1988 that with a high degree of reliability warming (increase in the mean global temperature by around 0.5 °C in this century) can be connected with the anthropogenic greenhouse effect, he stirred up a storm of critics. "It is time to stop waffling so much and say the evidence is pretty strong that the greenhouse effect is here." - he said in his interview to a journalist from New York Times. Thus, the statement of Hansen had an unusual political effect and drew many scientists and politicians of the world to this problem.

At that time many climatologists did not agree with Hansen and considered that recent hot years were normal deviation from mean temperatures. However data confirming the opinion of Hansen are being accumulated. And in 1989 A. Strong from the National Oceanic and Atmospheric Administration reported that the measurements of the ocean surface temperatures conducted from a satellite during 1982-1988… showed that the world's oceans gradually but noticeably grew warmer by about 0.1 °C a year. Later on, some scientists agreed with Hansen that physical manifestations of the anthropogenic greenhouse effect are already definite. Richard Houghton and George Woodwell stated that the heat and drought that affected North America and other regions of the Earth in recent years concurred with the predictions of possible global warming. There were also other signs of increasing warming. These included information on decreasing size of the area of permafrost in Alaska and Canadian Arctic, on rising mean temperatures in Canadian lakes, on decreased maximum yearly extension of ice cover in Antarctica and Arctic, as well as on the diminishing number of icebergs in Europe and other regions. Unusual climatic phenomena in recent years - the Hugo Hurricane, floods in Africa and South-Eastern Asia, storms in Europe, - have given rise to the warming that it is "a signal" of the growing greenhouse effect. According to ex-director of the US National Center of Atmospheric Research Dr. Walter Roberts [Source: Robert, Walter Orr, "It is Time to Prepare for Global Climate Changes". Conservation Foundation Letter, April 1983.],"the dust bowl in the USA in the middle of 1930s was the greatest climate disaster in the history of our country… However it could seem a childish game in comparison with the dust bowl of the 2040s. As a result of warming… natural precipitation can decrease by 40 %, summers will get hotter, evaporation from the earth's surface will increase, soils will dry out, and winds will raise soils to the sky…"

In December 1988, having revised the strategy for the policy of climate change, the UN General Assembly approved the establishment of the Intergovernmental Panel on Climate Change. And in 1989 at an annual meeting the heads of seven large democratic states recognized the necessity of adopting a world convention on global climate change aimed at mitigation of anthropogenic greenhouse gas emissions.

For millenniums one natural human desire was to change the environment. At present we all of a sudden find ourselves on the verge of huge climate change resulting from human activities. Unfortunately these climate changes are unplanned and often uncontrolled and can entail catastrophic effects.

Climate on the Earth is determined by intricate interactions between the atmosphere, world oceans, ice caps, animals, vegetation and sedimentary rocks. When speaking of "a climate system" scientists mean all natural factors which form the climate in interaction. This system includes at least four main components: atmosphere, hydrosphere, lithosphere and biosphere. When a climatic system is in equilibrium - as it had been before the technological revolution - the solar radiation absorbed is balanced by the surface radiation of the Earth and atmosphere. The anthropogenic factors that produce an accumulation of solar energy impact the thermal balance, changing the climate. The factors which actively influence the solar energy balance include technological gases called greenhouse gases.

Greenhouse gases create a screen in the atmosphere that retains the infrared radiation resulting in the heating of the Earth is surface and lower layers of the atmosphere. Traces of these gases were present in the atmosphere almost through the whole history of the Earth. The most significant natural greenhouse gas is water vapor. The next in this row of greenhouse gases - carbon dioxide (CO2) - has either natural or anthropogenic origin. Through the entire history of the Earth it entered the atmosphere from volcanic activities, and its balance was kept on by the biota due to natural circulation. Without CO2 the temperature of the Earth surface would have been by around 33 °C lower than at present creating extremely unfavorable living conditions for animals and vegetation.

Scholars know how the chemical composition of the atmosphere has been changing during the last 160 thousand years. These data were obtained from the analysis of air bubbles in the ice cores pulled from a depth of 2 km at the "Vostok" station in Antarctica and in Greenland. The data indicate that in warm periods concentrations of CO2 and CH4 were some 1.5 times higher than in cold drift periods. These findings support the assumption expressed in 1861 by John Tyndall that the history of Earth's climate changes can be explained by changes in the atmospheric concentrations of carbon dioxide.

Carbon dioxide increases in the atmosphere not only in this natural way, but also due to human activities, mainly from combustion of fossil fuels and forest destruction. Therefore it is necessary to differentiate between the natural greenhouse effect and anthropogenic, enhanced greenhouse effect (or global warming).

The natural greenhouse effect keeps the thermal balance of Earth's atmosphere favorable for animals and vegetation. The biota is also a natural temperature regulator because it can emit or absorb CO2 due to a complex feedback mechanism formed and "adjusted" over millions of years.

The anthropogenic greenhouse effect, on the contrary, disturbs the established thermal balance in the atmosphere-hydrosphere-lithosphere system and therefore can produce a catastrophic rise in the temperature of the Earth. The anthropogenic greenhouse effect is caused by increases in the atmospheric carbon dioxide . This will entail climate warming and hence increased melting of glaciers and rise in sea levels as well as drastic weather changes throughout the world.

Greenhouse effect. A car or a greenhouse are heated under the sun, because light energy sinking inside through the glass is absorbed and converted into the thermal energy that cannot pass through the glass (Fig. 2). When the heat is trapped in this way, temperature rises. The Earth's atmosphere is heated likewise: light goes through the atmosphere while greenhouse gases, that act as "a blanket" holding heat, absorb infrared radiation. For instance, the temperature and climate we are used to are ensured by carbon dioxide concentration in the atmosphere at the level of 0.03 %. By raising this concentration, we increase the tendency for climate warming. Thus, the higher the greenhouse gas concentration, the stronger the greenhouse effect.

Greenhouse gases make up around 0.1 % of the atmosphere, which is mainly comprised of nitrogen - 78 % and oxygen - 21 %. The main greenhouse gases enhancing anthropogenic changes in the atmosphere are carbon dioxide (CO2) methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs)

Forests on the Earth occupying around 28 of the land and the world's oceans occupying 70% of the total surface of the Earth can influence the global carbon cycle, the level of atmospheric CO2 and the climate. While growing, forests absorb carbon dioxide from the atmosphere and accumulate it in phytomass and forest humus. According to assessments of the World Wildlife Fund, forests account for 80 % of carbon contained in vegetation and 40 percent of the total soil carbon. Scientists estimated that every year 1.6±1.0 billion tons of carbon are emitted into the atmosphere due to destruction of forests and land use change.

Carbon dioxide concentration in the world's oceans is several times higher in the deep than at the surface. This is because the level of inorganic carbon dissolved in water in the form of bicarbonate ions in equilibrium with CO2 is almost two orders more than in the atmosphere. If life in the ocean ceases, concentration of inorganic carbon in the depth and at the surface will become equal, leading to manifold increase in the atmospheric CO2 concentration. Therefore, the ocean biota regulates atmospheric CO2 concentration and through this maintains the surface temperature within the limits optimal to the life. A number of climatologists suggest that the world's oceans have a great potential to absorb CO2, and when water temperature rises, the capability of the ocean to absorb carbon increases. Thus, we can infer that the world ocean will probably play a stabilizing role in the carbon dioxide balance in global warming.