The amount of CO2 has increased
due to the increase of many kinds of burning activities such as fuel burning, industrial activities or daily human activities (burning forest for their accommodation or livestock). Burning forest can release the CO2 into the air and it goes in very quickly (for the reason that the characteristic of plants is to fix the CO2 not going into the atmosphere). When the number of plant area decreases, the CO2 can increasingly go into the air much more, finally, it can accumulate the heat from the UV radiant in the atmosphere and within the earth.