Conversations with the Earth Tom Burbine tburbine@framingham.edu 8/8/2019 Conversations with the Earth Tom Burbine tburbine@framingham.edu

06/16/10

Albedo Albedo is the reflectivity of the surface

Albedo goes from 0 to 1 High albedo – reflective Low albedo - absorbing

Planetary Energy Balance Equation Exercise 5 1) What does energy balance mean?

2) If we want to determine the energy emitted by the Earth, what do we have to assume about the Earth?

3) What is the formula for the energy flux from a blackbody?

4) What must we multiply this equation by if we want to determine the energy emitted by the whole Earth?

Area of sphere = 4R2 Area of Earth = 4Rearth2

5) What is the equation for the energy emitted by the Earth?

6) The energy absorbed by the Earth’s surface from the Sun will equal what minus what?

7) What is the Solar Flux on the Earth?

S = Solar Flux = 1366 W/m2

8) To determine energy intercepted by Earth from Sun, you need to multiply the Solar Flux by what?

Area of Earth that intercepts Sun’s rays = R2

9) What do you have to multiply the Solar flux by to determine how much energy is reflected?

Area of Earth that intercepts Sun’s rays = R2 Albedo = A

10) So the energy intercepted minus the energy reflected equals what 10) So the energy intercepted minus the energy reflected equals what? This is the energy absorbed by the Earth.

11) Equate the energy emitted by the Earth and the energy absorbed by the Earth to determine the energy balance equation

T4 =(S/4)(1-A)

12) From the Planetary Energy Balance Formula, calculate what the temperature is equal to?

T = [(S/4)(1-A)]1/4

13) Using the Planetary Enjergy Balance Equation, what should be the temperature of the Earth? S = 1366 W/m2 A = 0.30  = 5.67 x 10-8 W/(m2 K4)

14) The mean surface temperature of the Earth is 288 K, why is the calculated temperature lower than the real temperature?

http://www.hulu.com/watch/23343/scientific-american-frontiers-hot-planet-%E2%80%93-cold-comfort

Any Questions?