Page 121 - Science Course 1 (Book 2)

Mo9-L4a: How is Energy Transferred in the Atmosphere?

Radiation Balance Thermal Energy Transfer

The amount of radiation Earth receives from the Sun Conduction occurs when the atmosphere touches
is the same as the amount Earth radiates into the Earth.
atmosphere.
Conduction is the transfer of thermal energy by
This radiation balance maintains an overall collisions between particles of matter.
temperature on Earth.
Thermal energy always moves from an object with a
higher temperature to an object with a lower
temperature.
Incoming radiation Outgoing radiation

Wavelength (μm)

The Greenhouse Effect

Some of the gases in the atmosphere, called greenhouse gases, act like the glass of a greenhouse,
allowing sunlight to pass through but preventing some of Earth’s IR energy from escaping.

When gases in Earth’s atmosphere direct radiation back toward Earth’s surface, this warms Earth’s
atmosphere more than normal, creating a heat surplus.
CO2
Carbon
dioxide

CH4
Methane
Gas

H2O
Water
Vapor

The gases that trap IR best are water vapor, carbon dioxide,
and methane.
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