Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere, even then carbon dioxide is considered to be responsible for green house effect. Explain why?
Carbon dioxide gas is confined to troposphere only. Normally it forms about 0.03 per cent by volume of the atmosphere. With the increased use of fossil fuels, a large amount of carbon dioxide gets released into the atmosphere. Excess of $$CO_2$$ in the air is removed by green plants and this maintains an appropriate level of $$CO_2$$ in the atmosphere.
Green plants require $$CO_2$$ for photosynthesis and they, in turn, emit oxygen, thus maintaining the delicate balance. As you know, deforestation and burning of fossil fuel increases the $$CO_2$$ level and disturb the balance in the atmosphere. The increased amount of $$CO_2$$ in the air is mainly responsible for global warming.