The physics and chemistry of the greenhouse effect
Point 4 of 7 — The Atmosphere: Layers, the Greenhouse Effect and Ozone DepletionQuestion bank: 0 questions (0 with pictures)
04 The physics and chemistry of the greenhouse effect
Short-wave solar radiation passes through the atmosphere with little absorption and heats the surface.
The warmed surface emitslong-wave infrared. Molecules that change dipole moment when they vibrate — CO₂, CH₄, H₂O, N₂O, O₃ — absorb that radiation and re-emit it in all directions, part of it back to the ground.
N₂ and O₂, being symmetric diatomics, do not absorb infrared and are not greenhouse gases — a favourite exam distinction.
Thenatural greenhouse effect keeps the Earth near 15 °C instead of −18 °C; the problem is theenhancedeffect caused by extra gases.
Sources of the main gases: CO₂ from burning fossil fuels, cement manufacture and deforestation · CH₄ from rice paddies, ruminants, landfills and gas leaks · N₂O from fertilisers and biomass burning · CFCs from old refrigerants and solvents · tropospheric O₃ from the photochemical reaction of NOx with hydrocarbons in sunlight (photochemical smog).
Feedbacks amplify the change: melting ice lowers albedo, warmer air holds more water vapour, and thawing permafrost releases methane.
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