Heating the Atmosphere

1. Heating the Atmosphere Pgs. 10 - 13

2. Energy in the Atmosphere • Radiation is the transfer of energy as electromagnetic waves. • Earth receives energy from the sun through the process of radiation. • The Earth only receives two-billionths of the sun’s energy. • When this energy reaches a surface, it heats it. • The division of the energy the Earth receives is discussed next.

3. Sun’s Energy on Earth • The energy the Earth receives from the sun is divided up as follows: • 25% is scattered and reflected by clouds and air molecules. • 20% is absorbed by ozone, clouds, and atmospheric gases. • 50% is absorbed by the Earth’s surface. • 5% is reflected by the Earth’s surface

4. Conduction • Conduction is the transfer of thermal energy from one material to another by direct contact. • A hot frying pan is in direct contact with a flame. • The food in the frying pan is in direct contact with the pan and gets cooked. • A hot surface of the Earth is in direct contact with air molecules and heats them.

5. Convection • Convection is the transfer of thermal energy by the circulation or movement of a liquid or gas. • Most thermal energy in the atmosphere moves by convection. • Air molecules become heated and become less dense and rises. • Cool air is more dense and sinks. • The cool air is eventually heated and rises again. • The hot air is eventually cooled and sinks.

6. Greenhouse effect • 50% of the energy that reaches the Earth is absorbed by the Earth. • This energy cannot be held by the Earth and is reradiated away. • Carbon dioxide and water vapor prevent the energy from escaping the atmosphere. • The atmosphere stays warm. • This is known as the greenhouse effect. • The atmosphere acts like a greenhouse.

7. Global Warming • Gases that trap heat within the atmosphere are known as greenhouse gases. • Greenhouse gases like carbon dioxide have been increasing due to human activity. • Some scientists believe that this has caused the global temperature to rise. • A rise in the average global temperature is called global warming.

8. The Radiation Balance • To have Earth remain livable, the amount of energy coming in and the amount leaving Earth should be equal. • 30% of the energy coming in is reflected back into space. • Most of the 70% that is absorbed will eventually be reradiated out into space. • The balance between incoming and outgoing energy is known as the radiation balance. • If too much energy is kept in, the global climate would be affected and could cause major changes in plant and animal life.

9. Keeping the Earth Livable • Global warming has become a topic of conflict in recent years. • Some scientists believe the Earth has gone through warm and cold periods in the past and that global warming is a natural process. • Others believe that recent human activity has caused an increase in greenhouse gases and global warming.