Planetary Engineering 1

1. Planetary Engineering 1 Climate Modeling Class Exercise

2. Zero-Dimensional GEBM Global energy balance: Radiative equilibrium (in = out)

3. Goal: Planets’ Temperatures Important Fact: Sun heats less the farther it is. Important Factor: How does S change with orbit?

4. Recall from Topic 1: Change in solar flux: sun  earth At photosphere surface, solar flux ~ 6.2.107 W-m-2 At Earth’s orbit, solar flux ~ 1360 W-m-2

5. Two Spheres Surrounding Sun Total energy flux the same through each sphere R2 = 2 x R1 R2 R1 The same area at R2 intercepts only 1/4 of energy it intercepts at R1  Flux decreases as R-2

6. For Earth Global energy balance: Radiative equilibrium (in = out) Thus, TRAD= 255 K

7. What about other planets? How does Trad change with orbit?

8. What about other planets? How does Trad change with orbit? Planet Distance Albedo Outgoing IR Trad from sun [A.U.] [W-m2] [K] Mercury 0.39 0.06 Venus 0.72 0.76 Earth 1.00 0.30 238 255 Mars 1.52 0.16 Jupiter 5.20 0.51 Saturn 9.54 0.50 Uranus 19.18 0.66 Neptune 30.06 0.62

9. For Mars Tsurface ≈ Trad. How warm can we make its surface?

10. For Mercury Tsurface ≈ Trad. How cool can we make its surface?

11. Venus? Why can’t we adjust Venus the same way?

12. End Planetary Engineering 1