Key Words radiation budget electromagnetic spectrum albedo Understand the concept of radiation and heat exchange Outline factors that control incoming and outgoing radiation in Earth’s atmosphere understand the concept of albedo

Sun releases different forms of energy called electromagnetic radiation. Earth absorbs and returns some of this energy slowly, keeping an average surface temperature of 15 degrees.

Energy is transferred by these methods: 1.Radiation - hands warming over a fire. Energy transferred through space – no medium. All energy from the sun reaches us by radiation. 2. Conduction - a hot pot handle on the stove. Energy transferred through the collision of particles. Occurs quickly with rocks, metals, sand, water. 3. Convection - boiling water. Energy carried by the movement of fluid particles. Water and air.

Energy radiates at the speed of light – 300, 000,000 m/s. Radiating energy from the Sun travels like a wave. Waves go up and down quickly (short wavelengths), or slowly (long wavelengths). Short wavelengths carry more energy.

Types of Electromagnetic Radiation

X-rays and gamma rays: Short wavelength - high energy. Dangerous. Reflected safely away by upper-atmosphere. Ultraviolet waves: Causes cancer. Most rays absorbed by ozone layer. Visible light: Electromagnetic energy we can see. Energy that reflects off Earth and objects on Earth. Infrared: Electromagnetic energy we feel as heat. Type of energy that all objects absorb and release into the atmosphere as they cool. Radio and microwaves have long wavelength, low energy.

30% reflected 70% radiated back

51% absorbed directly by ground and oceans. All absorbed energy is transformed into infrared energy that eventually radiates away to space. Small amount transferred to air by convection and conduction. Helps earth maintain steady living conditions.

Some of the absorbed energy radiating off Earth bounces back off of clouds and molecules in the atmosphere. Greenhouse gases are natural or polluting gases that trap heat energy and prevent it from being radiated back into space. Carbon dioxide (CO 2 ) and methane (CH 4 ) are biggest contributors to the “Greenhouse effect” and Global Warming.

Albedo is the ratio of solar energy reflected by an object compared to the solar energy absorbed by the object. More reflective a surface - the higher the albedo. The lighter colour the surface– the higher the albedo. LOW ALBEDO: Dry land absorbs energy and radiates the energy captured to surroundings – hot areas. HIGH ALBEDO: Snow reflects most of the Sun’s energy back to space. It absorbs and radiates NO heat - colder areas. 30% is reflected directly the Earth – visible light, UV, X-rays

100 ◦C Energy absorbed 30 ◦C 100 ◦C Water has a high specific heat capacity- the amount of heat needed to raise the temperature.

Summer – Oceans absorb energy keeping land nearby cooler. Winter – Oceans radiate stored energy keeping land nearby warmer. Water acts to limit extreme temperature changes. Water is a heat sink – it absorbs a lot of energy to get hot and radiates heat captured slowly. Land is a poor heat sink – it absorbs very little energy to get hot and radiates the heat quickly.