How Co 2 molecule structure is responsible for trapping the heat?

How Co2   molecule structure is responsible for trapping the heat?


1 Answers

Aman Bansal
592 Points
12 years ago

Dear  Manoj,

Molecules and atoms have the ability to absorb and emit different types of energy: 

• Energy from the excitation of electrons such as from heat

• Energy from rotational motion allowing molecules to rotate upon their centre of gravity

• Energy from vibrational motion which is lost and gained as a result of the contraction and bending of the bonds between the atoms

Each of these kinds of energy relate to different parts of the spectrum. Electrical energy is most apparent in the ultraviolet and visible parts of the spectrum and would have a typical wavelength of 1 micrometer. Vibrational energy has a typical wavelength of 3 micrometers and occurs in the infrared and near infrared parts of the spectrum. Rotational energy has a considerably longer wavelength, in the order of 100 micrometers, and is found in the far infrared and microwave parts of the spectrum.

Within a molecule, the type of atomic grouping and bonding determines the specific wavelength of absorption and emission. Consequent to which is the stretching of the carbon-hydrogen bond in CH2 and CH3 groups involving energy within the infrared spectrum with a wavelength of 3.3 to 3.4 micrometers.

The gases that we collectively term the greenhouse gases have the same infrared vibrational wavelength as the thermal radiation that is emitted from Earth into space, thus allowing for the absorption of some of that thermal radiation.

The principal greenhouse gas is water vapour, which for all intents and purposes is entirely natural. By volume it accounts for 26 times the quantity of all the other greenhouse gases. However, it has a very small global warming potential (GWP) and hence it contributes between 38% and 71% of the total greenhouse effect. Overlapping forcings prevent the attribution of a specific value.

The next four greenhouse gases in order of their contribution to global warming are carbon dioxide, methane, nitrous oxide and dichlorodiflouromethane or CFC22. All the other greenhouse gases contribute less than 1% to global warming. They are numerous and include the synthetic suites of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydroflurrocarbons (HFCs). The most potent of the greenhouse gases in terms of GWP is sodium hexaflouride, just one unit of this causes a much warming over a 100 year period as 35,000 units of CO2 would.

In terms of the natural carbon cycle, the decomposition of vegetable matter together with CO2 from the soil releases 88 billion tons of CO2 per year. At the same time, soil and biomass sequester 90 billion tons and thus there is a net reduction of 2 billion tons of atmospheric CO2 (the oceans also act as a carbon sink and remove an additional 1 billion tons of CO2 per year).

Decomposition also results in the release of methane gas through the process od biomethanation or methanogenesis. This is accounted for within the figures for CO2 but in the coming years there could be a huge increase in the amount of CH4 released. Some 70 billion tons are trapped within the peat layers beneath the Siberian permafrost, already a million square kilometres of permafrost has melted and if this continues, as all indicators suggest, then we would see substantial quantities of CH4 being released. This has a GWP of 23 so is potentially more of a problem than the CO2 we emit.


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Aman Bansal

Askiitian Expert

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