The Earth emits infrared (IR) radiation as part of its energy balance with the Sun. Here’s how it happens step by step:
1. Absorption of Solar Energy
- The Sun’s energy reaches Earth mainly as visible light and some ultraviolet (UV) radiation.
- The land, oceans, and atmosphere absorb much of this energy, warming the planet’s surface.
2. Re-radiation as Infrared
- Warm objects emit electromagnetic radiation, with the wavelength depending on their temperature.
- Earth’s average surface temperature (~15 °C or 288 K) means it radiates mainly in the mid-infrared range (about 4–100 μm, peaking near 10 μm).
3. Role in the Greenhouse Effect
- Some of the emitted IR escapes directly to space.
- Greenhouse gases (CO₂, CH₄, water vapor) absorb certain IR wavelengths, then re-emit the energy in all directions — including back toward Earth — trapping heat and keeping the planet warmer.
4. Continuous Process
- This emission happens day and night, everywhere on Earth.
- The balance between incoming solar radiation and outgoing infrared radiation determines whether the planet warms, cools, or stays stable.