The Greenhouse Effect | Physics for GCSE/IGCSE - Year 11 PDF Download

The Greenhouse Effect

• Without an atmosphere, Earth's surface temperature would plummet to around -180°C during nighttime, akin to the Moon's surface.
  • This cooling occurs because Earth's surface would radiate all absorbed sunlight back into space.
• The temperature of Earth is influenced by factors governing the equilibrium between incoming and outgoing radiation.
• Predominantly, Earth receives its warmth from solar thermal radiation.
  • Simultaneously, Earth emits its own thermal radiation, albeit at a longer wavelength than that received from the Sun, given Earth's lower surface temperature.
• Certain atmospheric gases, like water vapor, methane, and carbon dioxide (known as greenhouse gases), trap and redirect longer-wavelength infrared radiation from Earth, hindering its escape into space.
• These gases absorb infrared radiation and subsequently re-emit it back toward the Earth's surface.
• This mechanism elevates Earth's temperature beyond what it would be without these gases in its atmosphere.

• The Earth's temperature is influenced by various factors, including how quickly sunlight and infrared radiation from the Sun are:
  • Reflected away from the Earth into space.
  • Absorbed by either the Earth's atmosphere or its surface.
  • Emitted from both the Earth's surface and its atmosphere back into space.
• The Greenhouse Effect is driven by the absorption and emission of radiation on Earth.
  • It's a natural process that enhances the Earth's surface temperature using sunlight.
• Sunlight's thermal radiation enters the Earth's atmosphere, where:
  • Part of it is reflected back into space.
  • Unreflected radiation is absorbed and re-emitted by greenhouse gases.
• The absorbed radiation subsequently heats both the atmosphere and the Earth's surface.
  • This phenomenon resembles the process occurring in a greenhouse, maintaining a warm, humid environment conducive for plant growth.