Increase in the amount of CO2 in air results in:
Green House Effect
Increase in amount of CO2 in air results in global warming and enhanced greenhouse effect.
Earth is heated by a part of reflected radiation (from the surface) and this heat is trapped by the atmosphere. Certain gases like CO2 increase the amount of heat energy trapped leading to what is termed as enhanced greenhouse effect. This phenomenon has led to global warming which is climate change driven by a steady increase in average temperature of earth's atmosphere in the last many decades.