1. Powering Earth’s Climate
The Sun:
Powering Earth’s Climate

2. Climate System
- the complex set of components that interact with each other to produce Earth’s climate.
Includes air, land, liquid water, ice, and living things

3. The Sun
Earth’s climate system is powered by the Sun. When the solar energy interacts with the components, they create our climate zones.
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 of the Earth is about 15 °C)

4. The Balance of Energy on Earth
Almost all the energy on Earth comes from the Sun
The Sun emits 3 types of radiation which are absorbed by the Earth’s Surface:
Ultraviolet radiation, visible light and infrared radiation
Ultraviolet Radiation: a form of invisible higher-energy radiation
Infrared Radiation: a form of invisible lower-energy radiation

5. Earth Absorbs Energy from the Sun
30% of the energy from the Sun is reflected back to space by clouds, particles in the atmosphere and the Earth’s surface.
The remaining 70% is absorbed by Earth’s surface, clouds, and certain gases in the atmosphere

6. Earth’s Surface Emits Energy
Energy can be converted from one form to another
Earth’s surface gains thermal energy and its temperature rises.
The surface then emits infrared radiation out.
The amount of energy radiated by the Earth’s system is equal to the amount of energy Earth’s system absorbs from the Sun.

7. Latitudes and Climate Zones
Lower Latitude
The climate is warmer at lower latitudes because the energy from the Sun hits the Earth’s surface directly
Radiation goes through less of the atmosphere, reducing the amount that is absorbed and reflected

8. Latitudes and Climate Zones
Higher Latitude
The climate is colder at higher latitudes because the energy from the Sun hits the surface at an angle, spreading the energy over a larger area
Radiation goes through more of the atmosphere, increasing the amount that is absorbed and reflected

9. How does Earth’s movement affect our climate?
Rotation – the earth spins completely around on its axis every 24 hours
At any given time, half of the earth is in darkness, other half illuminated by the sun – day and night
West to east rotation determines:
Direction in which the wind blows
Ocean current flow

10. How does Earth’s movement affect our climate?
Revolution – the earth makes one complete cycle around the sun ~365 days
The seasons are due to the Earth’s tilt and revolution, not distance from the Sun!
North Pole slanted towards sun for half the year = summer in northern hemisphere;
North Pole slanted away from the sun for the other half = winter in the northern hemisphere