Greenhouse Effect

Solar radiation, infrared absorption, and global temperature

The Sun emits primarily visible light, which passes through Earth's atmosphere and warms the surface. The warm surface radiates infrared (IR) radiation back toward space. Greenhouse gases (CO₂, CH₄, H₂O, N₂O) absorb and re-emit IR in all directions, trapping energy in the lower atmosphere. This natural greenhouse effect raises Earth's average temperature from ~255 K to ~288 K (about +33°C). Increasing CO₂ from pre-industrial 280 ppm to today's 420+ ppm has enhanced this effect, causing ~1.1°C of warming. The relationship is roughly logarithmic: each doubling of CO₂ adds about 3°C (climate sensitivity). Methane is ~80× more potent per molecule but exists in much smaller quantities.