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the breathing of living animals.
These natural emissions are in equilibrium with the absorption from forests plants and, even more, from marine algae of plankton and also from the fixation in the shells of many species of mollusks.
CO2 amount in the atmosphere is increasing of 0.45% every year.

CH4
This gas is present in the atmosphere with 1.75 ppm, or 0.000175%, but in the same 1860, it was only 0.848 ppm.

CH4 is imortant because it's reported as much more effective as a greenhouse gas than CO2, from 20 to 30 times, by the different scientific sources.
Its permanence in the atmosphere is less than CO2, only 12 years, because it can be oxidized by the photochemical reactions of our atmosphere.
Methane has increased its concentration, but the most recent researches, mentioned in the Italian version of the site www.lenntech.com, (a Dutch company working on air and water purification technologies) from which I take part of the data, affirm that CH4 increase will cease and become stable or inferior to the actual concentration, but not all scientific sources agree with this esteem for the future.

The main human sources are oil industry, as a waste in all its processes (20%); immediately after, there are the emissions of excrements fermentation and decomposition in animal breeding farms (18%), paddy fields (17%) and rubbish discharges (10%) and so on.

The natural sources of methane are the oceans, natural anaerobic fermentations in swamps and in the soil.
The Lenntech site reports a yearly increase of 0.60%, while Wikipedia reports and average yearly increase of 1.1-1.4% .

N2O
This gas is today present for 0.312 ppm (285 in 1860), but it's reported on Wikipedia as 200 times more effective as greenhouse gas than CO2, with a long persistance of 120 years.The human sources are the excessive use of nitrogenated fertilizers in agriculture, already containing nitrates (NO3-) and nitrites (NO2-) or ammonium (NH4+) that are oxidized by the nitrifying bacteria of the soil, in addition to the nitrogen naturally present in the soils, as part of its natural cycle between soil and atmosphere.
Also many industrial chemical processes are important N2O sources, like Al and solvents industries.
The overall human emissions are reported by the Lenntech site as 8 millions tons/year, mainly absorbed by oceans.

Other gases that can give a contribution even much higher, at equal concentration, than CO2, like CFC (chlorofluorocarbides), HCFCs (hydrogen chlorofluorocarbides) and HFC (hydrogen fluorocarbides) for their high persistence in the atmosphere, that don't exist in nature but has been massively produced in the last century as very useful refrigerating gases.
Today, most of the Countries have banned their production, but their persistence (up to 265 years, in the average, for HFC) makes sensible their contribution to global warming, despite their concentration is below 1 ppb (part per billion).
Every CFC molecule is effective as about 10,000 CO2 molecules, only to give an example.

Learn more about this author, Aldo Bonincontro.
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