Topic 8.6 Greenhouse Effect Global Warming Topic 8.6 Greenhouse Effect
Remember… The absorbed solar energy is re-radiated at longer wavelengths (in the infrared region of the spectrum) Infrared 70%
Absorption by the Atmosphere Various gases in the atmosphere can absorb radiation at this longer wavelength (resonance) H O They vibrate more (become hotter) O What happens to the gases when they absorb the radiation? Vibrate more Become hotter No change A & B C H H C H H H O
Greenhouse gases These gases are known as “Greenhouse” gases. They include carbon dioxide, methane, water and N2O. O H O H H C H H C H O
Balance There exists a balance between the energy absorbed by the earth (and its atmosphere) and the energy emitted. Energy in Energy out
Balance This means that normally the earth has a fairly constant average temperature (although there have been big changes over thousands of years) Energy in Energy out
Balance Without this normal “greenhouse effect” the earth would be too cold to live on. Is the greenhouse effect good for us? Why? Yes No Energy in Energy out
Bath balance It’s a bit like trying to add water to a bath with the plug hole open.
Bath balance The water reaches a certain level but no higher because the amount of water leaving eventually equals the amount entering
Bath balance The water reaches a certain level but no higher because the amount of water leaving eventually equals the amount entering Energy entering the earth Earth’s temperature Energy leaving the earth
Greenhouse gases Most scientists believe that we are producing more of the gases that absorb the infrared radiation, thus upsetting the balance and producing a higher equilibrium earth temperature.
Bath with the plug half in! This is like trying to fill a bath, but now with the plug half covering the hole.
A new balance Eventually the water will reach a steady level again, but higher than before. New HIGHER equilibrium temperature
What might happen?
Evidence? Ice core research Weather records Remote sensing by satellites Measurement!