The Greebhouse Emission Effect

	Sunlight brings energy into the climate system; most of it is absorbed by the oceans and land.
The Natural Greenhouse Effect: It is the warming effect on the Earth due to solar radiations that are trapped within the Earth's atmosphere. Trapping being carried by the gases called the greenhouse gases (GHG). GHG defined by the Kyoto Protocol are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), HFCs, PFCs, and SF₆. The insulating property of these GHG gases is similar to that of the glass in a greenhouse: they allow solar heat entering into the system, but discourage its escape.
	Heat (infrared energy) radiates outward from the warmed surface of the Earth.
	Some of the infrared energy is absorbed by greenhouse gases in the atmosphere, which re-emit the energy in all directions.
	Some of the infrared energy further warms the Earth.
	Some of the infrared energy is emitted into space.

Amplified Greenhouse Effect (man-induced):
	Higher concentrations of CO₂ and other "greenhouse" gases trap more infrared energy in the atmosphere than occurs naturally. The additional heat further warms the atmosphere and Earth’s surface.
	(Pic: Greenhouse Effect: Koshland-science-museum.org )

The Sun radiates thermal energy in all directions. Before reaching the Earth, 1/3 of the solar radiations is reflected back into space. Most of this reflection is carried out by the clouds and the aerosols. The rest is carried out by the brighter features of the Earth: the snow, icebergs and deserts. On reaching the Earth, the balance of 2/3 radiations is mostly absorbed by the Earth's surface.

Whatever is the amount of thermal radiations absorbed by the Earth, it has to be radiated back to the space, otherwise the Earth would be too warm for dwelling.

The Earth radiates thermal energy of lesser energy (longer wavelengths) than the thermal energy it receives from the Sun which is much hotter. For the Earth to reflect back thermal radiations of these wavelengths, its surface would have to be mathematically be at a temperature of - 19^oC.

But the actual temperature of the Earth is much warmer, 14^o C, as we feel it now. This is due to the natural blanketing effect of the greenhouse gases which keeps the Earth about 33^oC (14^oC+19^oC) warmer. Without these greenhouse gases in the atmosphere, the Earth would be too cold for living dwelling.

Man-Induced Greenhouse Effects
Unfortunately due to changes and new quality demands in our way of life, more energy is needed (for example increased cooling and heating systems in buildings, advanced infrastructure and transport system operating at bulleting speed, increased population with rapid economic growth in China, India and Brazil.) The related human activities have undesirably resulted in higher rate of greenhouse gas emission.

The increased emission of the greenhouse gases, prominently, carbon dioxide, increases the blanketing effect. This means more radiations are trapped within the atmosphere, causing more warming. Snow and ice begin to melt. Since they also reflect the solar radiations, their disappearance means more solar radiations stay trapped in the Earth's atmosphere. The melting consequently exposes the darker lands and water surfaces beneath. Being darker, they absorb more radiations, causing more warming. This warming in turn causes more melting. This cascading effect is called the 'ice-albedo feedback'. It amplifies greenhouse effect and contributes to global warming.

As a result of this greenhouse warming, higher rate of vaporization occurs at the oceans, producing more water vapor which is also a greenhouse gas. They reflect the solar radiations back to the Earth causing warming and generating more water vapor.

The growing concern is the resultant excessive global warming; which has been shown to have altered, and will continue to alter global climate significantly.

Reference and Related News:

Climate Change 2007 : The Physical Science Basis - AR4 - IPCC
Greenhouse Effect: Koshland-science-museum.org
97% of climatologists say global warming is occurring and caused by humans (Jan 22.2009)
Global Warming Frequently Asked Questions - NOAA
Why Global Warming May Be Fueling Australia's Fires Feb 10, 2009
Australian bushfires pump out millions of tonnes of carbon Feb 13, 2009

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