Question

If there is no $CO_2$ in the atmosphere, what would happen to the earth’s temperature?
A. It would be less than the present.
B. It would be the same as present.
C. It would be higher than present.
D. It depends on the $O_2$ content of air.

Answer 1

$CO_2$ absorbs less heat per molecule than the greenhouse gases methane or nitrous oxide, but it's more abundant and it is present in the environment much longer. Carbon dioxide is an important greenhouse gas that helps to trap heat in our atmosphere.

Complete answer:
To answer this question, first, we need to know about the effect of carbon dioxide in our environment. Carbon dioxide atmosphere absorbs and stores the energy near the earth's surface when incoming solar radiation is bounced back to space. If there was no carbon dioxide then there would be no absorption of solar energy and hence the temperature of earth's surface would be less than the present level.
Now, let us find the solution from the option.
When carbon dioxide and various other air contaminants are present in the environment they soak sunlight that has reflected from the surface of the Earth. This results in a rise in the earth's optimum surface temperature and is known as global warming. When there is no carbon dioxide in the air, the temperature of the Earth's surface will be less than the present temperature.

Thus, the correct option is A. i.e. It would be less than the present.

Note: The carbon dioxide that gathers in the air covers the surface of the Earth. That is similar with a hot cover that captures the heat. This power raises the Earth’s surface optimum heats, temperature of oceans and melts down polar ice. As a consequence, sea level rises and weather changes.