The British scientists say , that global warming in the 20th century can be explained by a complex of the reasons both human and a natural origin.
In the model of a climate ,scientists have compared data of emissions of hotbed gases in an atmosphere, solar cycles, a level of ozone, sulfur and a volcanic dust.
Work was made in the center of forecasting and research of climate “Hadley†which is a part of the British governmental meteorological agency, and also in Rutherford - Appleton Laboratory. Results of work have been published in the magazine “Science”.
In the beginning of a century , the natural reasons rendered greatest influence on process of global warming, as scientists have found after the analysis of model.. Now warming is mainly caused by the human factor.
Scientists speak, that this work allows them to predict ,with greater confidence, the future contribution of the human to process of global warming.
Scientists write that more than 80 % of observable fluctuations of average temperatures, and also more than 60 % of fluctuations of temperatures of the ground for the periods from 10 - 50 years are caused by forces of an external source.
Average temperature near a surface of the Earth in last three decades increased on 0,2 degrees of Celsius each ten years.
Similar increase was observed between 1910 and 1945 , after that the temperature has stopped to raise - until the middle 1970. Until now, models of a climate with greater effort has explained warming in first half of century, as they ignored natural factors.
For the first time researches put side by side the most important reasons of human and natural character.
Authors of the science project tell, that their model considered changes in the structure of greenhouse gases in an atmosphere, including carbon dioxide and methane. The model also considered changes in the configuration of ozone in a troposphere and a stratosphere, and also changes in the structure of sulfur.
” When we have included both human, and natural factors “, - authors wrote. - ” we have concluded, that both anthropogenic, and natural factors are necessary for considering for an explanation of change of temperature on the surface of the Earth in 20th century Model successfully reproduces changes of temperature on a large proportion during 20th century “.
At the same time, scientists have noted, that the model does not explain changes of temperature of the Atlantic in the beginning of a century and fluctuation of temperature in the Northern Atlantic last thirty years. Scientists, however, consider, that they managed to reproduce the main tendencies in fluctuations of temperature during all century.
Their conclusion consists that present warming will proceed during following several tens years. By their calculations, it makes 2-3 degrees for hundred years.