The correct answer is: B. equilibrium temperature.
The equilibrium temperature is the temperature needed to keep the earth’s surface and the atmosphere in thermal equilibrium. This is the temperature at which the amount of energy absorbed by the earth from the sun is equal to the amount of energy radiated back into space by the earth.
The surface temperature is the temperature of the earth’s surface. This is the temperature that is measured by thermometers. The mean global surface temperature is the average of the surface temperatures of the earth’s land and ocean surfaces. Global temperature is the average temperature of the earth’s atmosphere.
The equilibrium temperature is different from the surface temperature and the mean global surface temperature because it takes into account the amount of energy that is radiated back into space by the earth. The surface temperature and the mean global surface temperature are only affected by the amount of energy that is absorbed by the earth from the sun.