Hello benllinliu,
I have some remarks concerning the “hydrosphere spending hypothesis”, specially about the supposed mechanism of decomposition of methane in the exosphere and the escape of the resulting hydrogen atoms into outer space. In the link you provided[1], which covers the hypothesis in some detail, an alternative to this mechanism is described and dismissed as “not validated strictly”:
Bates et al in 1950 proposed that the methane would be oxidized gradually by hydroxyl[10]. However, the hydroxyl oxidizing process was not validated strictly, and academic cycle often considered that whereabouts of the methane in the atmosphere is still a misty with necessary of further research[11], though the explanation of the methane oxidized gradually by hydroxyl is popular in the world now
Please note, the conclusion, that more research is needed, is based on an article from 1980. When we compare the quoted paragraph with the following survey from 2001 [2], which sums up the current knowledge about the methane cycle - including a table (4.2) detailing the methane budget based on three relatively recent studies (1991, 1997,1998) - we find that methane loss in the atmosphere is mainly caused by its reaction with OH in the troposphere, expressed by:
OH + CH4 -> CH3 + H2O
Minor losses are reported for the stratosphere by reactions with OH, Cl, and O(
1D). Losses in the exosphere are not mentioned.
Any comments?
-Bernd
References
[1]
The Science Forum[2]
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