Global geological methane emissions: an update of top-down and bottom-up estimates
A wide body of literature suggests that geological gas emissions from Earth’s degassing are a major methane (CH4) source to the atmosphere. These emissions are from gas-oil seeps, mud volcanoes, microseepage and submarine seepage in sedimentary (petroleum-bearing) basins, and geothermal and volcanic...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
BioOne
2019-11-01
|
| Series: | Elementa: Science of the Anthropocene |
| Subjects: | |
| Online Access: | https://www.elementascience.org/articles/383 |
| _version_ | 1819049909316222976 |
|---|---|
| author | Giuseppe Etiope Stefan Schwietzke |
| author_facet | Giuseppe Etiope Stefan Schwietzke |
| author_sort | Giuseppe Etiope |
| collection | DOAJ |
| description | A wide body of literature suggests that geological gas emissions from Earth’s degassing are a major methane (CH4) source to the atmosphere. These emissions are from gas-oil seeps, mud volcanoes, microseepage and submarine seepage in sedimentary (petroleum-bearing) basins, and geothermal and volcanic manifestations. Global bottom-up emission estimates, ranging from 30 to 76 Tg CH4 yr–1, evolved in the last twenty years thanks to the increasing number of flux measurements, and improved knowledge of emission factors and area distribution (activity). Based on recent global grid maps and updated evaluations of mud volcano and microseepage emissions, the global geo-CH4 source is now (bottom-up) estimated to be 45 (27–63) Tg yr–1, i.e., ~8% of total CH4 sources. Top-down verifications, based on independent approaches (including ethane and isotopic observations) from different authors, are consistent with the range of the bottom-up estimate. However, a recent top-down study, based on radiocarbon analyses in polar ice cores, suggests that geological, fossil (14C-free) CH4 emissions about 11,600 years ago were much lower (<15 Tg yr–1, 95% CI) and that this source strength could also be valid today. Here, we show that (i) this geo-CH4 downward revision implies a fossil fuel industry CH4 upward revision of at least 24–35%. (ii) The 95% CI estimates of the recent radiocarbon analysis do not overlap with those of 5 out of 6 other bottom-up and top-down studies (no overlap for the 90% CI estimates). (iii) The contrasting lines of evidence require further discussion, and research opportunities exist to help explain this gap. |
| first_indexed | 2024-12-21T11:39:38Z |
| format | Article |
| id | doaj.art-e0652fdb09314c4abce3b0f8c17d9134 |
| institution | Directory Open Access Journal |
| issn | 2325-1026 |
| language | English |
| last_indexed | 2024-12-21T11:39:38Z |
| publishDate | 2019-11-01 |
| publisher | BioOne |
| record_format | Article |
| series | Elementa: Science of the Anthropocene |
| spelling | doaj.art-e0652fdb09314c4abce3b0f8c17d91342022-12-21T19:05:21ZengBioOneElementa: Science of the Anthropocene2325-10262019-11-017110.1525/elementa.383358Global geological methane emissions: an update of top-down and bottom-up estimatesGiuseppe Etiope0Stefan Schwietzke1Istituto Nazionale di Geofisica e Vulcanologia, RomeEnvironmental Defense Fund, LondonA wide body of literature suggests that geological gas emissions from Earth’s degassing are a major methane (CH4) source to the atmosphere. These emissions are from gas-oil seeps, mud volcanoes, microseepage and submarine seepage in sedimentary (petroleum-bearing) basins, and geothermal and volcanic manifestations. Global bottom-up emission estimates, ranging from 30 to 76 Tg CH4 yr–1, evolved in the last twenty years thanks to the increasing number of flux measurements, and improved knowledge of emission factors and area distribution (activity). Based on recent global grid maps and updated evaluations of mud volcano and microseepage emissions, the global geo-CH4 source is now (bottom-up) estimated to be 45 (27–63) Tg yr–1, i.e., ~8% of total CH4 sources. Top-down verifications, based on independent approaches (including ethane and isotopic observations) from different authors, are consistent with the range of the bottom-up estimate. However, a recent top-down study, based on radiocarbon analyses in polar ice cores, suggests that geological, fossil (14C-free) CH4 emissions about 11,600 years ago were much lower (<15 Tg yr–1, 95% CI) and that this source strength could also be valid today. Here, we show that (i) this geo-CH4 downward revision implies a fossil fuel industry CH4 upward revision of at least 24–35%. (ii) The 95% CI estimates of the recent radiocarbon analysis do not overlap with those of 5 out of 6 other bottom-up and top-down studies (no overlap for the 90% CI estimates). (iii) The contrasting lines of evidence require further discussion, and research opportunities exist to help explain this gap.https://www.elementascience.org/articles/383geological methaneseepageglobal emission estimatesbottom-uptop-down |
| spellingShingle | Giuseppe Etiope Stefan Schwietzke Global geological methane emissions: an update of top-down and bottom-up estimates Elementa: Science of the Anthropocene geological methane seepage global emission estimates bottom-up top-down |
| title | Global geological methane emissions: an update of top-down and bottom-up estimates |
| title_full | Global geological methane emissions: an update of top-down and bottom-up estimates |
| title_fullStr | Global geological methane emissions: an update of top-down and bottom-up estimates |
| title_full_unstemmed | Global geological methane emissions: an update of top-down and bottom-up estimates |
| title_short | Global geological methane emissions: an update of top-down and bottom-up estimates |
| title_sort | global geological methane emissions an update of top down and bottom up estimates |
| topic | geological methane seepage global emission estimates bottom-up top-down |
| url | https://www.elementascience.org/articles/383 |
| work_keys_str_mv | AT giuseppeetiope globalgeologicalmethaneemissionsanupdateoftopdownandbottomupestimates AT stefanschwietzke globalgeologicalmethaneemissionsanupdateoftopdownandbottomupestimates |