B.2 Greenhouse effect

Objective notes

10 learning objectives

—B.2.1—Conservation of energy

• Conservation of energy.

—B.2.2—Emissivity

• Emissivity compares surface radiation per unit area with a black body: ε = power/(σT^4).

—B.2.3—Albedo

• Albedo = total scattered power / total incident power.

—B.2.4—Earth’s albedo variation

• Earth’s albedo varies daily with cloud formation and latitude.

—B.2.5—Solar constant S

• Solar constant S.

—B.2.6—Mean solar intensity

• Mean incoming solar intensity is S/4 due to planetary geometry.

—B.2.7—Greenhouse gases

• Main greenhouse gases: CH4, H2O, CO2 and N2O from natural and human sources.

• Greenhouse gases have both natural and human-created origins.

—B.2.8—Infrared absorption

• Greenhouse gases absorb IR via molecular energy levels.

• Radiation is re-emitted in all directions.

—B.2.9—Greenhouse models

• Explain greenhouse effect using resonance and molecular energy-level models.

—B.2.10—Enhanced greenhouse effect

• Enhanced greenhouse effect = augmentation due to human activity.