The global climate change (the global warming) is the most serious ecological threat of the 21st century.

The wastes caused by human activities, are altering the chemical composition of the atmosphere through the buildup of green house gases.

The greenhouse gases serve as a screen in the atmosphere, that traps heat. The most considerable greenhousegases are water vapour, carbon dioxide, methane, and chlorofluorocarbons (CFCs).

Higher concentrations of these gases increase the greenhouse effect which results in the heating of the Earth's surface.

According to the climatologists' estimates, the increase of green house gases in the atmosphere resulted in the global climate warming: the average air temperature rose by 0.5-0.6 degrees C (in comparison with the pre-industrial period). By the beginning of 2000, this rise will be 1.2 degrees C and by 2025 it may reach 2.2-2.5 degrees C.

For the Earth's biosphere such climate change may have both positive and negative consequences:

-a change of adaptability of the natural association, for instance, the forests aptitude for the migration;
-a rise of the World ocean level (modern rate of the water rise is approximately 25 cm per 100 years) due to melting of the Greenland and Antarctic icy shields ;
-migration of hundreds of millions people because of the floods in the low coastal zones, in the deltas of the rivers and on the islands;
-an increase of the intensity of photosynthesis which can favourably influence the agricultural yields and forestry.

The emission of greenhouse gases can be reduced by decreasing fossil fuel consumption and stopping forest destruction.

Reference:
Global warming. The report of Green Peace. Pub.MGU, 1993.