Earth’s Energy Balance

Almost all the energy used on Earth to sustain life and cause our changing weather systems comes from the Sun.

Without this energy, (a) plants could not grow, and (b) the land, water and air would not stay warm enough for human survival.

(The average surface temperature is about 15 °C)

The earth must maintain an energy balance.

If the energy absorbed > energy radiated,the Earth heats up

If the energy absorbed < energy radiated,the Earth cools down

About 30% of the sun’s incoming energy is immediately reflected by the clouds, atmosphere and earth’s surface.

The rest is absorbed and radiated back into space more slowly.

Transfer of Energy:

Energy can be transferred from one place to another by 3 methods:

(1) Radiation

(2) Conduction

(3) Convection

Radiation:Transfer of energy by means of waves

Unlike water and sound waves, radiation does not require a medium; therefore, energy from the sun can reach us by traveling through space

Radiation can be absorbed, reflected or transmitted.

Visible light is one form of radiation that is part of the electromagnetic spectrum.

Frequency is measured in Hertz (Hz), the number ofCycles (or vibrations) every second

Conduction:Transfer of energy through the collision of particles. (in solids only)

When particles are heated, they vibrate quickly, collide with other particles, and transfer some energy to them.

If the temperature is increased, the particles vibrate more quickly, resulting in an increase in particle collisions.

Convection:Transfer of energy by the movement of particles in a fluid (a liquid or a gas)

When particles in a liquid or gas heated, they move farther apart so that part of the fluid becomes less dense. As a result, the fluid rises, and is replaced by cooler, denser fluid.

The continuous flow of fluid in this manner is known as a convection current.