As the air over the earth surface gets warmed due to the solar radiation coming from the sun which directly heats the upper atmosphere of the earth and thus the air gets heated up and rest light or energy is absorbed by the ground and reflected into the atmosphere.
Similarly, the altitude has a major role to play in this process as the place near the tropics and equator air is less dense and hence higher absorption as compared to the higher latitudes the air becomes denser and hence lear absorption takes place.
Also with regards to the atmospheric cloud patterns the earth temperatures changes as these bring winds and rainfall and these cool the temperature over the hotter places like air moves from high pressure to low pressure and visa Versa.
Mountains isolated many groups that migrated to the region. Dense forest served as a barrier to migration across the region. Vast plains facilitated the migration of people across the region.
