Earth's Energy Budget

• Earth receives only a very small portion of the sun’s energy, yet this energy is responsible for powering the motion of the atmosphere, the oceans, and many processes at Earth’s surface.
  • About one-third of the sun’s incoming energy is reflected back out to space.
  • About one-half of the energy striking Earth is absorbed by Earth’s surface.
  • Solar radiation is made up of different types of radiation (including infrared, visible light, and ultraviolet).

Greenhouse Effect

• Incoming solar radiation is in close balance with the energy that leaves the atmosphere; otherwise Earth would heat up or cool down.
  • Excess carbon dioxide and other gases may disrupt this balance, creating a greenhouse effect.

Radiation and Convection

• Earth’s surface is heated unequally.
• When air or water is heated, the molecules move faster and farther apart, reducing their density and causing them to rise.
• Cooler air or water molecules move more slowly and are denser than warm air or water.

• Warm air or water rising coupled with cooler air or water descending forms a cyclic rising/falling pattern called convection.
  • Radiation and convection from Earth’s surface transfer thermal energy.
  • This energy powers the global circulation of the atmosphere and the oceans on our planet.

Clouds and Weather

• Clouds: As bodies of water (oceans, lakes, rivers, etc.) absorb thermal energy, the water evaporates causing the air to be warm and moist.
  • Warm, moist air is less dense than cold, dry air, so it rises relative to colder, drier air.
  • As warm, moist air rises, it gives off some thermal energy as the moisture condenses, forming clouds.
  • Clouds are not gaseous water vapor; rather they are minute, condensed water particles.
• Some thunderstorms are formed where the land is strongly heated.
• Hurricanes form over warm, tropical water and are fed by the energy of that water.