GG101 Lecture Notes - Lecture 13: Infrared, Shortwave Radiation, Contrail
LESSON 13 Climate Change
- The greenhouse effect
o atmosphere is relatively translucent to solar radiation (incoming shortwave
radiation)
o but is largely opaque to terrestrial longwave radiation (thermal infrared
radiation)
o Shortwave radiation (insolation) passes through the atmosphere where only
some is absorbed
o Most solar radiation is transmitted to the surface where some is reflected back
and the balance is absorbed by the surface
o absorbed solar energy at the surface and in the atmosphere is converted to
other forms of energy including longwave radiation
o radiation is emitted by the surface and atmosphere
o greenhouse gases in the atmosphere absorb much of the longwave radiation
emitted from the surface, and the greenhouse gases emit longwave radiation,
much of which is redirected back to surface
o Cycling of longwave energy between the surface and the atmosphere is the
greenhouse effect
o The greenhouse effect is important in sustaining habitable conditions on Earth o If the
concentration of greenhouse gases increases, the process of absorbing
longwave radiation in the lower atmosphere and emitting longwave radiation
back to surface would be made more efficient. As a result, the lower atmosphere
would warm
- Primary greenhouse gases are
o Water vapour – most important
Human activities influence the distribution of water vapour and cloud
development – cirrus clouds arise from condensation trails from planes o Carbon dioxide
• Fossil fuel combustion, industrial processes, and deforestation
• 8 billion metric tonnes per year
