If there was no CO2 in the earth's atmosphere, the temperature of earth's surface would be:

Explanation

Carbon dioxide is a greenhouse gas with a warming effect of 60%. Greenhouse gases are essential for keeping the earth warm and hospitable. They prevent a substantial part of longwave radiations emitted by the earth to escape into space and radiate a part of this energy back to the earth. The phenomenon is called greenhouse flux. Because of greenhouse flux, the mean annual temperature of the earth is 15°C. Recently the concentration of greenhouse gases has started rising that is resulting in increasing the mean global temperature. It is called global warming. Deforestation has reduced carbon dioxide assimilation. The excess remains in the air. Excessive use of fossil fuel is adding more CO 2 to the atmosphere. This causes the greenhouse effect.