Greenhouse gases in the atmosphere absorb most of the Earth's emitted _____, which heats the lower atmosphere.

The correct answer is Infrared radiation.

Key Points

• Green House Effect
  • The greenhouse effect is caused due to Infrared rays. 
  • The rest of the infrared radiation, the thick red arrow, is absorbed by the greenhouse gases and clouds in the atmosphere and then re-emitted in all directions as shown by the collection of orange arrows.
  • This ability to absorb and re-emit infrared radiation is a critical requirement for greenhouse gases.
  • The greenhouse effect is the process where infrared radiation from the Sun is absorbed by water vapor and certain gases in the atmosphere, thus increasing the temperature on the Earth.
  • If the concentration of greenhouse gases increases, then more infrared radiation will be absorbed and emitted back toward Earth's surface, creating an enhanced or amplified greenhouse effect.
  • It occurs due to the increase in greenhouse gases.
  • The major greenhouse gases are
    • Water Vapour - causes about 36% - 70% of the greenhouse effect
    • Carbon dioxide (CO₂) causes 9 - 26%
    • Methane (CH₄) causes 4 - 9% and ozone (O₃)

Additional Information

• Ultraviolet (UV) radiation
  • It is a form of non-ionizing radiation that is emitted by the sun and artificial sources, such as tanning beds. 
• Cosmic rays
  • They are atom fragments that rain down on the Earth from outside of the solar system.
• Microwaves
  • They are a portion or "band" found at the higher frequency end of the radio spectrum, but they are commonly distinguished from radio waves because of the technologies used to access them.