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Objectives for today Describe what happens to solar energy that reaches Earth. Summarize the processes of radiation, thermal conduction, and convection. Explain the relationship between the greenhouse effect and global warming.
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How is food heated in an oven? How is food heated on a range top?
Atmospheric HeatingAtmospheric Heating
Objectives for today
• Describe what happens to solar energy that reaches Earth.
• Summarize the processes of radiation, thermal conduction, and convection.
• Explain the relationship between the greenhouse effect and global warming.
Atmospheric HeatingAtmospheric Heating All energy on Earth comes from the Sun.All energy on Earth comes from the Sun. Earth and its atmosphere are also warmed Earth and its atmosphere are also warmed
by energy from the sun.by energy from the sun. There are three types of heating: Radiation, There are three types of heating: Radiation,
Convection, and ConductionConvection, and Conduction
Radiation:Energy Transfer by WavesRadiation:Energy Transfer by Waves The Earth receives energy from the sun by The Earth receives energy from the sun by radiation. Radiation is the transfer of radiation. Radiation is the transfer of energy as electromagnetic waves.energy as electromagnetic waves.
Although the sun radiates a huge amount Although the sun radiates a huge amount of energy, Earth receives only about two-of energy, Earth receives only about two-billionths of this energy billionths of this energy
Conduction: Energy Transfer by Conduction: Energy Transfer by ContactContact Thermal conduction is the Thermal conduction is the transfer of thermal energy through a transfer of thermal energy through a material.material.
Conduction can also occur within an Conduction can also occur within an object.object.
Thermal energy is always transferred from Thermal energy is always transferred from warm to cold areas. warm to cold areas.
When air molecules come into direct When air molecules come into direct contact with the warm surface of Earth, contact with the warm surface of Earth, thermal energy is transferred to the thermal energy is transferred to the atmosphere.atmosphere.
Convection: Energy Transfer by Convection: Energy Transfer by CirculationCirculation Convection is the Convection is the transfer of thermal energy by the transfer of thermal energy by the circulation or movement of a liquid or circulation or movement of a liquid or gas.gas.
Most thermal energy in the Most thermal energy in the atmosphere is transferred by atmosphere is transferred by convection.convection.
As air is heated, it becomes less As air is heated, it becomes less dense and rises. dense and rises.
Cool air is denser, so it sinks. Cool air is denser, so it sinks.
Convection: Energy Transfer by Convection: Energy Transfer by Circulation Continued...Circulation Continued...
As the cool air sinks, it pushes the As the cool air sinks, it pushes the warm air up. warm air up.
The cool air is eventually heated by The cool air is eventually heated by the Earth's surface and begins to rise the Earth's surface and begins to rise again. again.
This cycle of warm air rising and cool This cycle of warm air rising and cool air sinking causes a circular air sinking causes a circular movement of air, called a movement of air, called a convection convection current.current.
Atmospheric Heating
Objectives for today
• Describe what happens to solar energy that reaches Earth.
• Summarize the processes of radiation, thermal conduction, and convection.
• Explain the relationship between the greenhouse effect and global warming.
Energy in the Atmosphere
• The Greenhouse Effect and Life on Earth The greenhouse effect is the process by which gases in the atmosphere absorb thermal energy and radiate it back to Earth.•This process is called the greenhouse effect because the gases function like the glass walls and roof of a greenhouse, which allow solar energy to enter but prevent thermal energy from escaping.•About 70% of the radiation that enters Earth's atmosphere is absorbed by clouds and by the Earth's surface.
This energy is converted into thermal energy This energy is converted into thermal energy that warms the planet. that warms the planet.
Short-wave visible light is absorbed and Short-wave visible light is absorbed and reradiated into the atmosphere as long-reradiated into the atmosphere as long-wave thermal energy.wave thermal energy.
The atmosphere is like a warm blanket that The atmosphere is like a warm blanket that traps enough energy to make Earth livable.traps enough energy to make Earth livable.
Atmospheric Heating
• Greenhouse Gases and Global Warming Some scientists think that an increase of greenhouse gases in the atmosphere may be the cause of global warming. • The Radiation Balance: Energy In, Energy Out The amount of energy Earth receives and the amount of energy returned to space must be approximately equal.
How do differences in air density cause How do differences in air density cause convection currents?convection currents?
What is a green house gas?What is a green house gas? Describe three ways energy is transferred in Describe three ways energy is transferred in
the atmosphere.the atmosphere. What is the difference between green house What is the difference between green house
gases and global warming?gases and global warming?
Objectives for today
• Describe what happens to solar energy that reaches Earth.
• Summarize the processes of radiation, thermal conduction, and convection.
• Explain the relationship between the greenhouse effect and global warming.
