The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) the atmosphere will radiate energy in all directions.

1. The Greenhouse Effect on Earth

2. The Greenhouse Effect on Earth
Earth’s atmosphere is slightly warmer than
what it should be due to direct solar heating
because of a mild case of greenhouse
effect…
The ground is heated by visible and (some)
infrared light from the Sun.
The heated surface emits infrared light.
The majority of Earth’s atmosphere (N2 and
O2) are not good greenhouse gas.
The small amount of greenhouse gases
(H2O, CO2) traps (absorb and re-emit)
the infrared radiation, increasing the
temperature of the atmosphere…

3. Water On Earth
The condition is just right!
The combination of three factors: Distance to the Sun, the albedo, and the
greenhouse effect, make it possible for water to stay on Earth.
N2 and O2 are not greenhouse gas.
Not much CO2 in the atmosphere.
Variable amount of H2O in the atmosphere…regulated by the temperature.
The result is a mild greenhouse
effect…not too hot, and not too
cold, just the right temperature
for most of the water to stay in
liquid phase, and some to stay
in gas phase in the atmosphere
on the surface of the Earth…

4. Greenhouse Gases
● The primary components of Earth’s atmosphere, N2 and O2 do not
have absorption in the IR wavelength range, therefore, do not have
a significant role in setting the surface temperature of the planet…
●
Greenhouse gas are efficient in absorbing IR light…
The most important greenhouse gases are:
–H2O – Water vapor.
–CO2 – Carbon Dioxide
–CH4 – methane
The most abundant greenhouse gas in Earth’s atmosphere is water vapor.
Most of the greenhouse heating of Earth’s atmosphere is due to Water
vapor absorption of IR radiation emitted by Earth, and then transferring the
energy to the surrounding air molecule

5. Source of Water
●
Mt. St Helen eruption, 2004!
The terrestrial planets were built from rock and planetesimals. No gases or water can
condense at the high temperature near the Sun. So, where did the water on Earth come
from?
The water on Earth (and other terrestrial worlds) most likely was brought over by the
comets during the period of heavy bombardment about 4 billion years ago…
These water (and other gases) were trapped in the interior, and released by volcanic
activities…by Outgassing

6. My Two Cents…
●
It looks like most of the scientists agree that the global warming observed in the
last century were caused by human activity. However, as we tried to demonstrate
here, the global climate is a very complicated system.We understand the basic
principle of the climate system, but we still don’t understand how nature
regulates Earth’s climate over the long run, nor do we have the capability to
create a realistic climate model and be able to predict with any certainty the
effects of human activities on our climate system.
●
• My advices…
•
●
Keep an open mind.
●
Read, and think for yourself!
●
Do not rush into judgment (especially after you watch the movies).
●
Please trust the scientific community to come up with an honest answer…There
are enough check and balance in the scientific community to weed out the bad
theories…

7. •
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THANK YOU