The reproducing of modern climate and climate changes in 20 century by INM general circulation atmosphere and ocean model, and forecast of climate changes in 21 century using three scenarios with this model are shown. The model is capable to reproduce main features of observed climate and climate changes in 20 century. At the end of 21 century according to INM model global warming for scenarios A2, A1B, B1 equals 3.5, 2.6 and 2.0 degrees, it is not far from the average over 20 models that took part in the model comparison. The strongest warming is produced in Arctic and at the continents in midlatitudes. During global warming, the strongest decrease of sea ice is expected in Arctic at the end of summer, where sea ice can melt completely or almost completely at the end of 21 century. In winter decreasing of Arctic sea ice area can be as large as 20-30% of modern value. Sea level rise due to thermal expansion can be equal 13-20 cm in 2100 and 25-45 cm in 2200. During global warming, increasing of precipitation, increasing of river runoff and soil moisture in high and midlatitudes is expected by 10-30%. Decreasing of precipitation is expected in many subtropical regions, especially in Mediterranean and Central America. In Russia expected warming is stronger than the global averaged one. For scenario A1B, global warming is 3.3 degrees, winter warming in Russia is 4-6 degrees in the south, and 8-10 degrees in the north. In the coldest winter months warming can be stronger than that one in all winter months. In the warmest winter months warming can be smaller than that one in all winter months. Predicted summer warming in Russia equals 5-6 degrees in the south, and 3-4 degrees in the north. In the warmest summer months warming can be stronger than that one in all winter months. In the coldest summer months warming can be smaller than that one in all winter months. Over the most part of Russia increasing of precipitation by 1.1-1.5 times is expected. The exception is southern Russia, where decreasing of precipitation by 10-20% is predicted. At the end of 21 century increase of vegetation period by 20-50 days and decrease of number of frost days by 20-50 is predicted.