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Talk:Atmospheric methane

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Section sizes Section size for Atmospheric methane (11 sections) Section name Byte count Section total (Top) 8,161 8,161 Role in climate change 8,536 8,536 Sources 1,392 1,392 Measurement techniques 1,666 1,666 Global monitoring 12,174 12,174 Natural sinks or removal of atmospheric methane 8,128 14,146 Mean lifespan 3,182 3,182 Methanotrophs in soils and sediments 2,836 2,836 Removal technologies 1,440 1,440 Methane concentrations in the geologic past 9,181 9,181 References 127 127 Total 56,823 56,823

About the section 'Mean lifespan': I was surprised to see the numbers given here for the atmospheric lifetime of methane and I believe they are somewhat confused, in particular 'By 2013, methane's mean lifetime in the atmosphere was estimated to be twelve years.' Source [69] is the Guardian with no scientific source given. Source [29] is a report from 2013 - not 2023, when it was accessed - that is based on scientific literature, which cites the IPCC 2007 report. The IPCC 2007 gives a perturbation time of 12 years and an atmospheric lifetime of 8.7 years.

The turnover time of a gas is its atmospheric abundance divided by the total loss rate. The perturbation time includes feedback mechanisms and thus better describes how long emissions actually remain in the atmosphere (=lifespan?). Usually, the atmospheric lifetime is given as a turnover time.

Newer studies including the IPCC 2013 report typically use the numbers by Prather et al. 2012 [doi:10.1029/2012GL051440] given with 9.1 years, e.g. source [68] (also mentioned in this section) that analyzes factors that change the atmospheric lifetime.

Unfortunately, no source is given for 'As of 2001, the mean lifespan of methane in the atmosphere was estimated at 9.6 years.'

Given that number is correct, the first paragraph is then somewhat misleading if the lifetime actually drops from 9.6 to 9.1. The variation in the estimated OH sink (difficult to quantify), probably plays a significant role.

In total, I think some work is required here to put this paragraph in line with the scientific findings. Pelicanelson (talk) 13:15, 5 January 2024 (UTC)[reply]

Could CCAP be CCAC (abbreviation for Climate & Clean Air Coalition) instead? Thanks for your kind attention. ThomasYehYeh (talk) 06:04, 3 February 2024 (UTC)[reply]

"The direct radiative greenhouse gas forcing effect of methane relative to 1750 has been estimated at 0.5 W/m2 (watts per meter²) in the 2007 IPCC "Climate Change Synthesis Report 2007".: 38 " What the purpose for "0.5 W/m2" here, is it an increase from 1750's level? ThomasYehYeh (talk) 06:08, 3 February 2024 (UTC)[reply]