Consider a simple model in which Earth’s surface temperature is uniform and remains constant. In order to maintain therm

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Consider a simple model in which Earth’s surface temperature is
uniform and remains constant. In
order to maintain thermal equilibrium, Earth must radiate energy to
space just as quickly as it absorbs
radiation.
Q1) Sunlight strikes the Earth at a rate of 1.74 x 1017 W, but only
70% of that energy is absorbed by
the planet. (The rest is reflected back to space.) Given Earth’s
radius and assuming the planet has an
emissivity of 1, what should be Earth’s equilibrium surface
temperature?
A. 245 K (–28°C) C. 265 K (–8°C)
B. 255 K (–18°C) D. 275 K (+2°C)
Q2) Instead, Earth’s average surface temperature is 288 K (+15°C)
due to greenhouse gases in the
atmosphere that warm the planet by trapping radiation. What is
Earth’s effective emissivity in this
simple model?
A. 0.6 C. 0.8
B. 0.7 D. 0.9
Q3) If Earth could not radiate away the energy it absorbs from the
Sun, its temperature would
increase dramatically. Assume all of the energy absorbed by Earth
were deposited in Earth’s oceans
which contain 1.4 x 1021 kg of water. How long would it take the
average temperature of the oceans to
rise by 2°C?