Evaluation # 8

Hello Professor,

This blog will focus on the second part of the Climate lab. The reason being, is that in the lab, the concept was still a little fuzzy and by studying and depicting it here, I am hoping to fully understand the two dimensional climate model explained in Richars Wolfson's "Energy, Environment, and climate". 

The purpose of the two dimensional climate model is to illustrate in a simplified way how the earth's energy balance works and how the energy exchange between the surface and the atmosphere functions. As we know from previous chapters, the energy balance of the earth entails that the same amount of energy enters from the sun as it is reflected back to space. 

Due to the emissivity(the effectiveness of molecules in absorbing and radiating energy) of the molecules in the atmosphere, the manner in which the energy leaves the earth is not as uniform as when it enters. Almost 100% of the earth's energy is derived from the sun. Even though, the earth receives 235 W/m^2 of solar energy, not all of it reaches the surface. A large amount of the solar energy is directly reflected back to space by the greenhouse gases. This is attributed to their high emissivity rate, which is not constant and depends on the atmosphere's temperature and molecular concentration of greenhouse gases. 

The remainder of the solar energy that is not directly radiated back to space, reaches the earth's surface. Although the radiation of the surface depends on the surface's temperature, in total its emissivity is close to one. This means that the earth's surface absorbs and emits energy very well.  As a result, the energy that reaches the earth is reflected back to space. This is how the earth's energy balance occurs.

However, before earth's surface energy is reflected back to space, it is absorbed by the atmospheric gases of the lower atmosphere due to the difference in temperature between the earth's surface and the atmosphere. This difference in temperature, absorption of energy, and retention of energy is what we refer too as the greenhouse effect. One can go as far as to deduce that life is possible on earth due to the presence of greenhouse gases. Otherwise the earth's average temperature would be 254 Kelvin or -19. 15 Celsius, which would be way beyond water's freezing point.