[3] The simulation of climate and its changes is based on the INM atmosphere-ocean general circulation model [Diansky and Volodin, 2002; Volodin and Diansky, 2003; Volodin and Diansky, 2006]. The model resolution is 5 x 4 degrees by longitude and latitude, respectively, with 21 vertical levels from the Earth's surface up to a height of 30 km for the atmosphere, and 2.5 x 2 degrees by longitude and latitude, respectively, with 33 levels by depth for the ocean. The model describes all principal processes of a climate impact. Using the model, numerical experiments were performed with given timing for all main influences of climate impact in the XX-XXII centuries: the concentration of greenhouse gases (carbon dioxide, methane, and nitrous oxide) as well as volcanic and sulfate aerosols, and the solar constant. The external influences are given by observation data for the time period before 2000 and by scenarios A2, A1B, and B1 for the time period after 2000.
[4] The numerical experiments include:
[5] (1) Simulation of climate changes between 1871 and 2000 based on the observed change in all external influences.
[6] (2) Simulation of climate changes in the XX-XXII centuries for scenarios A2, A1B, and B1 of the variation in the concentrations of greenhouse and other gases in the XXI century. The solar constant and concentration of volcanic aerosols in these experiments were fixed at the level of the year 2000. For the XXII century, all external influences were assumed to be fixed at the level of the year 2100.
[7] (3) Simulation of the XXI century climate, where all gas concentrations and the remaining influences were assumed to be equal to the values observed in 2000 (experiment 2000).
[8] (4) Control experiment, where all external influences correspond to 1871 data. This experiment is needed to estimate the inner variability of the climate system.
[9] The concentration of carbon dioxide (which is the key greenhouse gas) was 289 ppm in 1871, 370 ppm in 2000, and can reach 550, 690, and 830 ppm for scenarios B1, A1B, and A2, respectively, in 2100. The XX century was characterized by increased concentrations of the remaining greenhouse gases and sulfate aerosol. The solar constant also has a tendency of growth; however, its contribution to the temperature increase in the XX century constitutes merely 10 to 15% of the contribution of greenhouse gases. The maxima of volcanic aerosol concentrations correspond to powerful volcanic eruptions with dust particles falling into the upper layers of the atmosphere and being able to remain there from a few months to a few years.
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