Heating of the Atmosphere

1. Heating of the Atmosphere

2. What could cause such a spectacular, swirling funnel of air? • For many people, this sight is unfamiliar. It is a tornado. • Tornadoes happen when heat is rapidly transferred between layers in the atmosphere.

3. How Heat Moves • Changes in weather involve air movements, formation of clouds and precipitation. • Energy is needed to make all these things happen. That energy comes from the sun. • Heat energy enters and moves through the atmosphere in three different ways: • Radiation • Conduction • Convection

4. Radiation • Hot bodies such as the sun radiate their energy mainly in the form of short waves. • These short waves are seen as visible light. • Cooler bodies such as the Earth radiate their energy in longer waves. These waves are called infrared waves.

5. Conduction • An object receives heat when it comes into direct contact with a hotter object. • A pan on a hot stove is heated mainly by conduction. The air touching a hot radiator is heated mainly by conduction. • So is the air that touches warm ground or a warm ocean.

6. Convection • Convection is the most effective form of heat transfer in liquids and gases. • A kettle of water on a hot stove is an example of heating by convection. The bottom of the kettle is heated by conduction. • The water near the bottom then heats also by conduction. Heating makes the water expand and become less dense. • The denser cold water above it sinks, forcing up the warm water. • A steady flow called a convection current forms. In time, all the water in the kettle is heated.

7. Convection is very important in moving heat through the atmosphere. • It transfers heat from one place to another. • For example, convection removes heat from hot beaches. Winds from the tropics carry heat away and into middle latitude. • The transfer of warm or cold air by horizontal winds is called advection.

8. Earth’s Heat Budget • Ideally just as much energy enters Earth as leaves. When this is true, Earth’s heat budget is in balance. • If Earth’s heat budget was out of balance, Earth would gradually heat up or cool down. • The only way energy can enter or leave Earth is by radiation. There are not enough molecules in space for conduction or convection. https://www.youtube.com/watch?v=D_Qmue54W14

9. The Greenhouse Effect • How does the atmosphere resemble a greenhouse? • To extend the growing season, many farmers use greenhouses. • A greenhouse traps heat so that days that might be too cool for a growing plant can be made to be just right. • Similar to a greenhouse, greenhouse gases in the atmosphere keep Earth warm.

10. The exception to Earth’s temperature being in balance is caused by greenhouse gases. • But first the role of greenhouse gases in the atmosphere must be explained… • Greenhouse gases warm the atmosphere by trapping heat. • Some of the heat that radiates out from the ground is trapped by greenhouse gases in the troposphere. • Like a blanket on a sleeping person, greenhouse gases act as insulation for the planet.

11. The warming of the atmosphere because of insulationby greenhouse gases is called the greenhouse effect. • Greenhouse gases are the component of the atmosphere that moderate Earth’s temperatures.

12. Greenhouse Gases • Greenhouse gases include CO 2 , H 2 O, methane, O 3 , nitrous oxides (NO and NO 2 ), and chlorofluorocarbons (CFCs). All are a normal part of the atmosphere except CFCs. • This table shows how each greenhouse gas naturally enters the atmosphere.

13. Different greenhouse gases have different abilities to trap heat. • For example, one methane molecule traps 23 times as much heat as one CO 2 molecule. One CFC-12 molecule (a type of CFC) traps 10,600 times as much heat as one CO 2 . • Still, CO 2 is a very important greenhouse gas because it is much more abundant in the atmosphere. https://www.youtube.com/watch?v=Hi3ERes0h84

14. Avery…the world is in your capable hands! Human Activity and Greenhouse Gas Levels • Human activity has significantly raised the levels of many of the greenhouse gases in the atmosphere. • Methane levels are about 2 1/2 times higher as a result of human activity. Carbon dioxide has increased more than 35%. CFCs have only recently existed. • What do you think happens as atmospheric greenhouse gas levels increase? • More greenhouse gases trap more heat and warm the atmosphere. • The increase or decrease of greenhouse gases in the atmosphere affect climate and weather the world over.

15. In Summary… • Radiation is the transfer of energy between two objects by electromagnetic waves. • In conduction, substances must be in direct contact as heat moves from areas of more heat to areas of less heat. • In convection, materials move depending on their heat relative to nearby materials. • The equator receives more solar energy than other latitudes. • Greenhouse gases include CO 2 , H 2 O, methane, O 3 , nitrous oxides (NO and NO 2 ), and chlorofluorocarbons (CFCs). • Tropospheric greenhouse gases trap heat in the atmosphere; greenhouse gases vary in their heat-trapping abilities. • Levels of greenhouse gases in the atmosphere are increasing due to human activities. https://www.youtube.com/watch?v=R_pb1G2wIoA