1. Solar constant The solar constant is the amount of incoming solar radiation per unit area, measured on the outer surface of Earth's atmosphere, in a plane perpendicular to the rays. Solar constant for Earth, S = 1350 W/m 2

2. Albedo Albedo is the fraction of sunlight which is reflected off a planet.  When an object reflects most of the light that hits it, it looks bright and it has a high albedo.  When an object absorbs most of the light that hits it, it looks dark. Dark objects have low albedo..

3. Earth’s Albedo  The average albedo of the Earth is about 0.30.  That means that about a third of the solar energy that gets to Earth is reflected out to space and about two thirds is absorbed

4. One layer model Assumptions: No atmosphere

5. Energy Balance P in = P out P in = (1-A) S π R E 2 P out = σ T E 4 4π R E 2 (1-A) S = σ T E 4 4

6. T earth = 257 K = -16° C = 3.2°F Energy Balance of the One layer model (1-A) S 4 σT4EσT4E Earth’s infrared radiation to spaceSolar radiation Earth

7. Calculating Surface Temperature of the Earth σ T 4 = S x ( 1- A) 4 Where S - Solar constant σ – Stephan constant - 5.67 x 10 -8 W/m 2 K 4 A - Albedo