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…
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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…
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
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

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