10. Climate 1 Overview

10. Climate 1 Overview - What regulates global temperature?...

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1 What regulates global temperature? Heat Balance: Energy in = Energy out Energy in = (Solar output)( π r 2 )(1-A)/(4 π R 2 ) Energy out = (4 π r 2 ) σ T 4 r = Earth radius R = Earth sun dist. A = Albedo T = °K Black Body Spectrum T is °K O 3 H 2 O, CO 2 , CH 4 Red shows absorption bands for greenhouse gases Total emitted = σ T 4 Calculate Expected Black Body Temperature (mainly IR) (mainly visible) Energy out = Energy in (per unit area basis) σ T 4 = (Solar output)(1-A)/(16 π R 2 ) For A = 0.30, T = 255 °K = -18°C Critical Factors: 1. Solar output 2. Earth-sun distance (R) 3. Albedo (A) 4. Greenhouse factor 5. Efficiency of heat transport from equator to poles dictates uniformity of T Note that if any of the parameters change, global temp can change. What happens on other rocky planets? Planet Black Body T* Observed T (°K) Venus 300 730 Earth 255 288 Mars 207 218 *calculated assuming A = 0.30 720 Clouds of Venus, Mariner 10 721 Mars from Viking, ice cap
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2 722 Earth from space Evidence that Earth was once colder Glacial landforms •cirque lakes •U shaped valleys •moraines
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10. Climate 1 Overview - What regulates global temperature?...

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