the Earth's temperature

• • if the rate of absorption of a body is greater than the rate of emission, the temperature increases
  • if the rate of absorption of a body is less than the rate of emission, the temperature decreases
• the Earth's temperature depends on:

  • concentration of greenhouse gases
  • rate at which light and infrared are absorbed and emitted by Earth's surface and atmosphere
• • visible light and high frequency infrared radiation absorbed by surface of Earth
  • so, internal energy of Earth increases and surface gets hotter
  • some energy transferred to atmosphere by conduction and convection
• • Earth radiates lower frequency infrared radiation
  • some infrared radiation transmitted through atmosphere into space
  • some is absorbed by greenhouse gases in atmosphere
  • greenhouse gases emit infrared radiation into space and back to Earth
  • Earth reabsorbs radiation, so internal energy increases, so surface gets hotter
• • intensity is power per unit area
  • as temperature of object increases, intensity of emitted wavelength increases
• • intensity increases more quickly for shorter than longer wavelengths
  • this can cause peak wavelength to decrease
  • peak wavelength is wavelength with the highest intensity
• • during the day, lots of radation transferred to Earth from Sun is absorbed so, local temperature increases
  • during the night, less radiation absorbed than emitted, so local temperature decreases
• • human activites release carbon dioxide
  • this causes more infrared radiation to be trapped in atmosphere and reabsorbed by Earth's surface
  • so, global temperature increases