Question

The sun continuously radiates energy into space in all directions. Some of the sun's energy is intercepted by the Earth. The average temperature of the surface of the Earth remains a little above 300 k. Why doesn't the Earth's temperature rise as it intercepts the sun's energy?

A. The Earth reflects the sun's light.

B. The Earth radiates an amount of energy into space equal to the amount it receives.

C. The energy only raises the temperature of the upper atmosphere and never reaches the surface.

D. The thermal conductivity of the Earth is low.

E. The heat is carried away from the Earth by convection currents.

Answer 1

B. The Earth radiates an amount of energy into space equal to the amount it receives.

Part of the solar energy is reflected by the Earth into space, this is known as albedo. The other part of the energy radiated by the Earth in the form of infrared radiation, is absorbed by the greenhouse gases, which cause most of this infrared radiation to be emitted into space. Therefore, the net flow of energy is zero.