The Global Methane Budget 2000–2017
<p>Understanding and quantifying the global methane (<span class="inline-formula">CH<sub>4</sub></span>) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of <span class="inline-fo...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-07-01
|
| Series: | Earth System Science Data |
| Online Access: | https://essd.copernicus.org/articles/12/1561/2020/essd-12-1561-2020.pdf |
| id |
doaj-3428135b6a9947e2bd9e10f79f51fb48 |
|---|---|
| record_format |
Article |
| collection |
DOAJ |
| language |
English |
| format |
Article |
| sources |
DOAJ |
| author |
M. Saunois A. R. Stavert B. Poulter P. Bousquet J. G. Canadell R. B. Jackson P. A. Raymond E. J. Dlugokencky S. Houweling S. Houweling P. K. Patra P. K. Patra P. Ciais V. K. Arora D. Bastviken P. Bergamaschi D. R. Blake G. Brailsford L. Bruhwiler K. M. Carlson K. M. Carlson M. Carrol S. Castaldi S. Castaldi S. Castaldi N. Chandra C. Crevoisier P. M. Crill K. Covey C. L. Curry C. L. Curry G. Etiope G. Etiope C. Frankenberg C. Frankenberg N. Gedney M. I. Hegglin L. Höglund-Isaksson G. Hugelius M. Ishizawa A. Ito G. Janssens-Maenhout K. M. Jensen F. Joos T. Kleinen P. B. Krummel R. L. Langenfelds G. G. Laruelle L. Liu T. Machida S. Maksyutov K. C. McDonald J. McNorton P. A. Miller J. R. Melton I. Morino J. Müller F. Murguia-Flores V. Naik Y. Niwa Y. Niwa S. Noce S. O'Doherty R. J. Parker C. Peng S. Peng G. P. Peters C. Prigent R. Prinn M. Ramonet P. Regnier W. J. Riley J. A. Rosentreter A. Segers I. J. Simpson H. Shi S. J. Smith S. J. Smith L. P. Steele B. F. Thornton H. Tian Y. Tohjima F. N. Tubiello A. Tsuruta N. Viovy A. Voulgarakis A. Voulgarakis T. S. Weber M. van Weele G. R. van der Werf R. F. Weiss D. Worthy D. Wunch Y. Yin Y. Yin Y. Yoshida W. Zhang Z. Zhang Y. Zhao B. Zheng Q. Zhu Q. Zhu Q. Zhuang |
| spellingShingle |
M. Saunois A. R. Stavert B. Poulter P. Bousquet J. G. Canadell R. B. Jackson P. A. Raymond E. J. Dlugokencky S. Houweling S. Houweling P. K. Patra P. K. Patra P. Ciais V. K. Arora D. Bastviken P. Bergamaschi D. R. Blake G. Brailsford L. Bruhwiler K. M. Carlson K. M. Carlson M. Carrol S. Castaldi S. Castaldi S. Castaldi N. Chandra C. Crevoisier P. M. Crill K. Covey C. L. Curry C. L. Curry G. Etiope G. Etiope C. Frankenberg C. Frankenberg N. Gedney M. I. Hegglin L. Höglund-Isaksson G. Hugelius M. Ishizawa A. Ito G. Janssens-Maenhout K. M. Jensen F. Joos T. Kleinen P. B. Krummel R. L. Langenfelds G. G. Laruelle L. Liu T. Machida S. Maksyutov K. C. McDonald J. McNorton P. A. Miller J. R. Melton I. Morino J. Müller F. Murguia-Flores V. Naik Y. Niwa Y. Niwa S. Noce S. O'Doherty R. J. Parker C. Peng S. Peng G. P. Peters C. Prigent R. Prinn M. Ramonet P. Regnier W. J. Riley J. A. Rosentreter A. Segers I. J. Simpson H. Shi S. J. Smith S. J. Smith L. P. Steele B. F. Thornton H. Tian Y. Tohjima F. N. Tubiello A. Tsuruta N. Viovy A. Voulgarakis A. Voulgarakis T. S. Weber M. van Weele G. R. van der Werf R. F. Weiss D. Worthy D. Wunch Y. Yin Y. Yin Y. Yoshida W. Zhang Z. Zhang Y. Zhao B. Zheng Q. Zhu Q. Zhu Q. Zhuang The Global Methane Budget 2000–2017 Earth System Science Data |
| author_facet |
M. Saunois A. R. Stavert B. Poulter P. Bousquet J. G. Canadell R. B. Jackson P. A. Raymond E. J. Dlugokencky S. Houweling S. Houweling P. K. Patra P. K. Patra P. Ciais V. K. Arora D. Bastviken P. Bergamaschi D. R. Blake G. Brailsford L. Bruhwiler K. M. Carlson K. M. Carlson M. Carrol S. Castaldi S. Castaldi S. Castaldi N. Chandra C. Crevoisier P. M. Crill K. Covey C. L. Curry C. L. Curry G. Etiope G. Etiope C. Frankenberg C. Frankenberg N. Gedney M. I. Hegglin L. Höglund-Isaksson G. Hugelius M. Ishizawa A. Ito G. Janssens-Maenhout K. M. Jensen F. Joos T. Kleinen P. B. Krummel R. L. Langenfelds G. G. Laruelle L. Liu T. Machida S. Maksyutov K. C. McDonald J. McNorton P. A. Miller J. R. Melton I. Morino J. Müller F. Murguia-Flores V. Naik Y. Niwa Y. Niwa S. Noce S. O'Doherty R. J. Parker C. Peng S. Peng G. P. Peters C. Prigent R. Prinn M. Ramonet P. Regnier W. J. Riley J. A. Rosentreter A. Segers I. J. Simpson H. Shi S. J. Smith S. J. Smith L. P. Steele B. F. Thornton H. Tian Y. Tohjima F. N. Tubiello A. Tsuruta N. Viovy A. Voulgarakis A. Voulgarakis T. S. Weber M. van Weele G. R. van der Werf R. F. Weiss D. Worthy D. Wunch Y. Yin Y. Yin Y. Yoshida W. Zhang Z. Zhang Y. Zhao B. Zheng Q. Zhu Q. Zhu Q. Zhuang |
| author_sort |
M. Saunois |
| title |
The Global Methane Budget 2000–2017 |
| title_short |
The Global Methane Budget 2000–2017 |
| title_full |
The Global Methane Budget 2000–2017 |
| title_fullStr |
The Global Methane Budget 2000–2017 |
| title_full_unstemmed |
The Global Methane Budget 2000–2017 |
| title_sort |
global methane budget 2000–2017 |
| publisher |
Copernicus Publications |
| series |
Earth System Science Data |
| issn |
1866-3508 1866-3516 |
| publishDate |
2020-07-01 |
| description |
<p>Understanding and quantifying the global methane (<span class="inline-formula">CH<sub>4</sub></span>) budget
is important for assessing realistic pathways to mitigate climate change.
Atmospheric emissions and concentrations of <span class="inline-formula">CH<sub>4</sub></span> continue to increase,
making <span class="inline-formula">CH<sub>4</sub></span> the second most important human-influenced greenhouse gas in
terms of climate forcing, after carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>). The relative
importance of <span class="inline-formula">CH<sub>4</sub></span> compared to <span class="inline-formula">CO<sub>2</sub></span> depends on its shorter
atmospheric lifetime, stronger warming potential, and variations in
atmospheric growth rate over the past decade, the causes of which are still
debated. Two major challenges in reducing uncertainties in the atmospheric
growth rate arise from the variety of geographically overlapping <span class="inline-formula">CH<sub>4</sub></span>
sources and from the destruction of <span class="inline-formula">CH<sub>4</sub></span> by short-lived hydroxyl
radicals (OH). To address these challenges, we have established a
consortium of multidisciplinary scientists under the umbrella of the Global
Carbon Project to synthesize and stimulate new research aimed at improving
and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper
dedicated to the decadal methane budget, integrating results of top-down
studies (atmospheric observations within an atmospheric inverse-modelling
framework) and bottom-up estimates (including process-based models for
estimating land surface emissions and atmospheric chemistry, inventories of
anthropogenic emissions, and data-driven extrapolations).</p>
<p><span id="page1564"/>For the 2008–2017 decade, global methane emissions are estimated by
atmospheric inversions (a top-down approach) to be 576 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> (range 550–594, corresponding to the minimum and maximum
estimates of the model ensemble). Of this total, 359 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> or
<span class="inline-formula">∼</span> 60 % is attributed to anthropogenic sources, that is
emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is
29 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> larger than our estimate for the previous decade (2000–2009),
and 24 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> larger than the one reported in the previous
budget for 2003–2012 (Saunois et al., 2016). Since 2012, global <span class="inline-formula">CH<sub>4</sub></span>
emissions have been tracking the warmest scenarios assessed by the
Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost
30 % larger global emissions (737 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, range 594–881)
than top-down inversion methods. Indeed, bottom-up estimates for natural
sources such as natural wetlands, other inland water systems, and geological
sources are higher than top-down estimates. The atmospheric constraints on
the top-down budget suggest that at least some of these bottom-up emissions
are overestimated. The latitudinal distribution of atmospheric
observation-based emissions indicates a predominance of tropical emissions
(<span class="inline-formula">∼</span> 65 % of the global budget, <span class="inline-formula"><</span> 30<span class="inline-formula"><sup>∘</sup></span> N)
compared to mid-latitudes (<span class="inline-formula">∼</span> 30 %, 30–60<span class="inline-formula"><sup>∘</sup></span> N)
and high northern latitudes (<span class="inline-formula">∼</span> 4 %, 60–90<span class="inline-formula"><sup>∘</sup></span> N). The most important source of uncertainty in the methane
budget is attributable to natural emissions, especially those from wetlands
and other inland waters.</p>
<p>Some of our global source estimates are smaller than those in previously
published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> lower due to
improved partition wetlands and other inland waters. Emissions from
geological sources and wild animals are also found to be smaller by 7 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> by 8 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, respectively. However, the overall
discrepancy between bottom-up and top-down estimates has been reduced by
only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane
budget include (i) a global, high-resolution map of water-saturated soils
and inundated areas emitting methane based on a robust classification of
different types of emitting habitats; (ii) further development of
process-based models for inland-water emissions; (iii) intensification of
methane observations at local scales (e.g., FLUXNET-<span class="inline-formula">CH<sub>4</sub></span> measurements)
and urban-scale monitoring to constrain bottom-up land surface models, and
at regional scales (surface networks and satellites) to constrain
atmospheric inversions; (iv) improvements of transport models and the
representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or
co-emitted species such as ethane to improve source partitioning.</p>
<p>The data presented here can be downloaded from
<a href="https://doi.org/10.18160/GCP-CH4-2019">https://doi.org/10.18160/GCP-CH4-2019</a> (Saunois et al., 2020) and from the
Global Carbon Project.</p> |
| url |
https://essd.copernicus.org/articles/12/1561/2020/essd-12-1561-2020.pdf |
| work_keys_str_mv |
AT msaunois theglobalmethanebudget20002017 AT arstavert theglobalmethanebudget20002017 AT bpoulter theglobalmethanebudget20002017 AT pbousquet theglobalmethanebudget20002017 AT jgcanadell theglobalmethanebudget20002017 AT rbjackson theglobalmethanebudget20002017 AT paraymond theglobalmethanebudget20002017 AT ejdlugokencky theglobalmethanebudget20002017 AT shouweling theglobalmethanebudget20002017 AT shouweling theglobalmethanebudget20002017 AT pkpatra theglobalmethanebudget20002017 AT pkpatra theglobalmethanebudget20002017 AT pciais theglobalmethanebudget20002017 AT vkarora theglobalmethanebudget20002017 AT dbastviken theglobalmethanebudget20002017 AT pbergamaschi theglobalmethanebudget20002017 AT drblake theglobalmethanebudget20002017 AT gbrailsford theglobalmethanebudget20002017 AT lbruhwiler theglobalmethanebudget20002017 AT kmcarlson theglobalmethanebudget20002017 AT kmcarlson theglobalmethanebudget20002017 AT mcarrol theglobalmethanebudget20002017 AT scastaldi theglobalmethanebudget20002017 AT scastaldi theglobalmethanebudget20002017 AT scastaldi theglobalmethanebudget20002017 AT nchandra theglobalmethanebudget20002017 AT ccrevoisier theglobalmethanebudget20002017 AT pmcrill theglobalmethanebudget20002017 AT kcovey theglobalmethanebudget20002017 AT clcurry theglobalmethanebudget20002017 AT clcurry theglobalmethanebudget20002017 AT getiope theglobalmethanebudget20002017 AT getiope theglobalmethanebudget20002017 AT cfrankenberg theglobalmethanebudget20002017 AT cfrankenberg theglobalmethanebudget20002017 AT ngedney theglobalmethanebudget20002017 AT mihegglin theglobalmethanebudget20002017 AT lhoglundisaksson theglobalmethanebudget20002017 AT ghugelius theglobalmethanebudget20002017 AT mishizawa theglobalmethanebudget20002017 AT aito theglobalmethanebudget20002017 AT gjanssensmaenhout theglobalmethanebudget20002017 AT kmjensen theglobalmethanebudget20002017 AT fjoos theglobalmethanebudget20002017 AT tkleinen theglobalmethanebudget20002017 AT pbkrummel theglobalmethanebudget20002017 AT rllangenfelds theglobalmethanebudget20002017 AT gglaruelle theglobalmethanebudget20002017 AT lliu theglobalmethanebudget20002017 AT tmachida theglobalmethanebudget20002017 AT smaksyutov theglobalmethanebudget20002017 AT kcmcdonald theglobalmethanebudget20002017 AT jmcnorton theglobalmethanebudget20002017 AT pamiller theglobalmethanebudget20002017 AT jrmelton theglobalmethanebudget20002017 AT imorino theglobalmethanebudget20002017 AT jmuller theglobalmethanebudget20002017 AT fmurguiaflores theglobalmethanebudget20002017 AT vnaik theglobalmethanebudget20002017 AT yniwa theglobalmethanebudget20002017 AT yniwa theglobalmethanebudget20002017 AT snoce theglobalmethanebudget20002017 AT sodoherty theglobalmethanebudget20002017 AT rjparker theglobalmethanebudget20002017 AT cpeng theglobalmethanebudget20002017 AT speng theglobalmethanebudget20002017 AT gppeters theglobalmethanebudget20002017 AT cprigent theglobalmethanebudget20002017 AT rprinn theglobalmethanebudget20002017 AT mramonet theglobalmethanebudget20002017 AT pregnier theglobalmethanebudget20002017 AT wjriley theglobalmethanebudget20002017 AT jarosentreter theglobalmethanebudget20002017 AT asegers theglobalmethanebudget20002017 AT ijsimpson theglobalmethanebudget20002017 AT hshi theglobalmethanebudget20002017 AT sjsmith theglobalmethanebudget20002017 AT sjsmith theglobalmethanebudget20002017 AT lpsteele theglobalmethanebudget20002017 AT bfthornton theglobalmethanebudget20002017 AT htian theglobalmethanebudget20002017 AT ytohjima theglobalmethanebudget20002017 AT fntubiello theglobalmethanebudget20002017 AT atsuruta theglobalmethanebudget20002017 AT nviovy theglobalmethanebudget20002017 AT avoulgarakis theglobalmethanebudget20002017 AT avoulgarakis theglobalmethanebudget20002017 AT tsweber theglobalmethanebudget20002017 AT mvanweele theglobalmethanebudget20002017 AT grvanderwerf theglobalmethanebudget20002017 AT rfweiss theglobalmethanebudget20002017 AT dworthy theglobalmethanebudget20002017 AT dwunch theglobalmethanebudget20002017 AT yyin theglobalmethanebudget20002017 AT yyin theglobalmethanebudget20002017 AT yyoshida theglobalmethanebudget20002017 AT wzhang theglobalmethanebudget20002017 AT zzhang theglobalmethanebudget20002017 AT yzhao theglobalmethanebudget20002017 AT bzheng theglobalmethanebudget20002017 AT qzhu theglobalmethanebudget20002017 AT qzhu theglobalmethanebudget20002017 AT qzhuang theglobalmethanebudget20002017 AT msaunois globalmethanebudget20002017 AT arstavert globalmethanebudget20002017 AT bpoulter globalmethanebudget20002017 AT pbousquet globalmethanebudget20002017 AT jgcanadell globalmethanebudget20002017 AT rbjackson globalmethanebudget20002017 AT paraymond globalmethanebudget20002017 AT ejdlugokencky globalmethanebudget20002017 AT shouweling globalmethanebudget20002017 AT shouweling globalmethanebudget20002017 AT pkpatra globalmethanebudget20002017 AT pkpatra globalmethanebudget20002017 AT pciais globalmethanebudget20002017 AT vkarora globalmethanebudget20002017 AT dbastviken globalmethanebudget20002017 AT pbergamaschi globalmethanebudget20002017 AT drblake globalmethanebudget20002017 AT gbrailsford globalmethanebudget20002017 AT lbruhwiler globalmethanebudget20002017 AT kmcarlson globalmethanebudget20002017 AT kmcarlson globalmethanebudget20002017 AT mcarrol globalmethanebudget20002017 AT scastaldi globalmethanebudget20002017 AT scastaldi globalmethanebudget20002017 AT scastaldi globalmethanebudget20002017 AT nchandra globalmethanebudget20002017 AT ccrevoisier globalmethanebudget20002017 AT pmcrill globalmethanebudget20002017 AT kcovey globalmethanebudget20002017 AT clcurry globalmethanebudget20002017 AT clcurry globalmethanebudget20002017 AT getiope globalmethanebudget20002017 AT getiope globalmethanebudget20002017 AT cfrankenberg globalmethanebudget20002017 AT cfrankenberg globalmethanebudget20002017 AT ngedney globalmethanebudget20002017 AT mihegglin globalmethanebudget20002017 AT lhoglundisaksson globalmethanebudget20002017 AT ghugelius globalmethanebudget20002017 AT mishizawa globalmethanebudget20002017 AT aito globalmethanebudget20002017 AT gjanssensmaenhout globalmethanebudget20002017 AT kmjensen globalmethanebudget20002017 AT fjoos globalmethanebudget20002017 AT tkleinen globalmethanebudget20002017 AT pbkrummel globalmethanebudget20002017 AT rllangenfelds globalmethanebudget20002017 AT gglaruelle globalmethanebudget20002017 AT lliu globalmethanebudget20002017 AT tmachida globalmethanebudget20002017 AT smaksyutov globalmethanebudget20002017 AT kcmcdonald globalmethanebudget20002017 AT jmcnorton globalmethanebudget20002017 AT pamiller globalmethanebudget20002017 AT jrmelton globalmethanebudget20002017 AT imorino globalmethanebudget20002017 AT jmuller globalmethanebudget20002017 AT fmurguiaflores globalmethanebudget20002017 AT vnaik globalmethanebudget20002017 AT yniwa globalmethanebudget20002017 AT yniwa globalmethanebudget20002017 AT snoce globalmethanebudget20002017 AT sodoherty globalmethanebudget20002017 AT rjparker globalmethanebudget20002017 AT cpeng globalmethanebudget20002017 AT speng globalmethanebudget20002017 AT gppeters globalmethanebudget20002017 AT cprigent globalmethanebudget20002017 AT rprinn globalmethanebudget20002017 AT mramonet globalmethanebudget20002017 AT pregnier globalmethanebudget20002017 AT wjriley globalmethanebudget20002017 AT jarosentreter globalmethanebudget20002017 AT asegers globalmethanebudget20002017 AT ijsimpson globalmethanebudget20002017 AT hshi globalmethanebudget20002017 AT sjsmith globalmethanebudget20002017 AT sjsmith globalmethanebudget20002017 AT lpsteele globalmethanebudget20002017 AT bfthornton globalmethanebudget20002017 AT htian globalmethanebudget20002017 AT ytohjima globalmethanebudget20002017 AT fntubiello globalmethanebudget20002017 AT atsuruta globalmethanebudget20002017 AT nviovy globalmethanebudget20002017 AT avoulgarakis globalmethanebudget20002017 AT avoulgarakis globalmethanebudget20002017 AT tsweber globalmethanebudget20002017 AT mvanweele globalmethanebudget20002017 AT grvanderwerf globalmethanebudget20002017 AT rfweiss globalmethanebudget20002017 AT dworthy globalmethanebudget20002017 AT dwunch globalmethanebudget20002017 AT yyin globalmethanebudget20002017 AT yyin globalmethanebudget20002017 AT yyoshida globalmethanebudget20002017 AT wzhang globalmethanebudget20002017 AT zzhang globalmethanebudget20002017 AT yzhao globalmethanebudget20002017 AT bzheng globalmethanebudget20002017 AT qzhu globalmethanebudget20002017 AT qzhu globalmethanebudget20002017 AT qzhuang globalmethanebudget20002017 |
| _version_ |
1724583112385495040 |
| spelling |
doaj-3428135b6a9947e2bd9e10f79f51fb482020-11-25T03:28:36ZengCopernicus PublicationsEarth System Science Data1866-35081866-35162020-07-01121561162310.5194/essd-12-1561-2020The Global Methane Budget 2000–2017M. Saunois0A. R. Stavert1B. Poulter2P. Bousquet3J. G. Canadell4R. B. Jackson5P. A. Raymond6E. J. Dlugokencky7S. Houweling8S. Houweling9P. K. Patra10P. K. Patra11P. Ciais12V. K. Arora13D. Bastviken14P. Bergamaschi15D. R. Blake16G. Brailsford17L. Bruhwiler18K. M. Carlson19K. M. Carlson20M. Carrol21S. Castaldi22S. Castaldi23S. Castaldi24N. Chandra25C. Crevoisier26P. M. Crill27K. Covey28C. L. Curry29C. L. Curry30G. Etiope31G. Etiope32C. Frankenberg33C. Frankenberg34N. Gedney35M. I. Hegglin36L. Höglund-Isaksson37G. Hugelius38M. Ishizawa39A. Ito40G. Janssens-Maenhout41K. M. Jensen42F. Joos43T. Kleinen44P. B. Krummel45R. L. Langenfelds46G. G. Laruelle47L. Liu48T. Machida49S. Maksyutov50K. C. McDonald51J. McNorton52P. A. Miller53J. R. Melton54I. Morino55J. Müller56F. Murguia-Flores57V. Naik58Y. Niwa59Y. Niwa60S. Noce61S. O'Doherty62R. J. Parker63C. Peng64S. Peng65G. P. Peters66C. Prigent67R. Prinn68M. Ramonet69P. Regnier70W. J. Riley71J. A. Rosentreter72A. Segers73I. J. Simpson74H. Shi75S. J. Smith76S. J. Smith77L. P. Steele78B. F. Thornton79H. Tian80Y. Tohjima81F. N. Tubiello82A. Tsuruta83N. Viovy84A. Voulgarakis85A. Voulgarakis86T. S. Weber87M. van Weele88G. R. van der Werf89R. F. Weiss90D. Worthy91D. Wunch92Y. Yin93Y. Yin94Y. Yoshida95W. Zhang96Z. Zhang97Y. Zhao98B. Zheng99Q. Zhu100Q. Zhu101Q. Zhuang102Laboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceGlobal Carbon Project, CSIRO Oceans and Atmosphere, Aspendale, VIC 3195 & Canberra, ACT 2601, AustraliaNASA Goddard Space Flight Center, Biospheric Science Laboratory, Greenbelt, MD 20771, USALaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceGlobal Carbon Project, CSIRO Oceans and Atmosphere, Aspendale, VIC 3195 & Canberra, ACT 2601, AustraliaDepartment of Earth System Science, Woods Institute for the Environment, and Precourt Institute for Energy, Stanford University, Stanford, CA 94305-2210, USAYale School of the Environment, Yale University, New Haven, CT 06511, USANOAA Global Monitoring Laboratory, 325 Broadway, Boulder, CO 80305, USASRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, the NetherlandsVrije Universiteit Amsterdam, Department of Earth Sciences, Earth and Climate Cluster, VU Amsterdam, Amsterdam, the NetherlandsResearch Institute for Global Change, JAMSTEC, 3173-25 Showa-machi, Kanazawa, Yokohama, 236-0001, JapanCenter for Environmental Remote Sensing, Chiba University, Chiba, JapanLaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceCanadian Centre for Climate Modelling and Analysis, Climate Research Division, Environment and Climate Change Canada, Victoria, BC, V8W 2Y2, CanadaDepartment of Thematic Studies – Environmental Change, Linköping University, 581 83 Linköping, SwedenEuropean Commission Joint Research Centre, Via E. Fermi 2749, 21027 Ispra (Va), ItalyDepartment of Chemistry, University of California Irvine, 570 Rowland Hall, Irvine, CA 92697, USANational Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Wellington, New ZealandNOAA Global Monitoring Laboratory, 325 Broadway, Boulder, CO 80305, USADepartment of Environmental Studies, New York University, New York, NY 10003, USADepartment of Natural Resources and Environmental Management, University of Hawai'i, Honolulu, HI 96822, USANASA Goddard Space Flight Center, Computational and Information Science and Technology Office, Greenbelt, MD 20771, USADipartimento di Scienze Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania Luigi Vanvitelli, via Vivaldi 43, 81100 Caserta, ItalyDepartment of Landscape Design and Sustainable Ecosystems, RUDN University, Moscow, RussiaImpacts on Agriculture, Forests, and Ecosystem Services Division, Centro Euro-Mediterraneo sui Cambiamenti Climatici, Via Augusto Imperatore 16, 73100 Lecce, ItalyResearch Institute for Global Change, JAMSTEC, 3173-25 Showa-machi, Kanazawa, Yokohama, 236-0001, JapanLaboratoire de Météorologie Dynamique, LMD-IPSL, Ecole Polytechnique, 91120 Palaiseau, FranceDepartment of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, Svante Arrhenius väg 8, 106 91 Stockholm, SwedenEnvironmental Studies and Sciences Program, Skidmore College, Saratoga Springs, NY 12866, USAPacific Climate Impacts Consortium, University of Victoria, University House 1, P.O. Box 1700 STN CSC Victoria, BC V8W 2Y2, CanadaSchool of Earth and Ocean Sciences, University of Victoria, P.O. Box 1700 STN CSC, Victoria, V8W 2Y2 BC, CanadaIstituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, via V. Murata 605 00143 Rome, ItalyFaculty of Environmental Science and Engineering, Babes Bolyai University, Cluj-Napoca, RomaniaDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USAJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USAMet Office Hadley Centre, Joint Centre for Hydrometeorological Research, Maclean Building, Wallingford OX10 8BB, UKDepartment of Meteorology, University of Reading, Earley Gate, Reading RG6 6BB, UKAir Quality and Greenhouse Gases Program (AIR), International Institute for Applied Systems Analysis (IIASA), 2361 Laxenburg, AustriaDepartment of Physical Geography and Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, SwedenCenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanCenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanEuropean Commission Joint Research Centre, Via E. Fermi 2749, 21027 Ispra (Va), ItalyDepartment of Earth and Atmospheric Sciences, City College of New York, City University of New York, New York, NY 10031, USAClimate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstr. 5, 3012 Bern, SwitzerlandMax Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, GermanyClimate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaClimate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaDepartment Geoscience, Environment & Society, Université Libre de Bruxelles, 1050-Brussels, BelgiumDepartment of Earth, Atmospheric, Planetary Sciences, Department of Agronomy, Purdue University, West Lafayette, IN 47907, USACenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanCenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanDepartment of Earth and Atmospheric Sciences, City College of New York, City University of New York, New York, NY 10031, USAResearch Department, European Centre for Medium-Range Weather Forecasts, Reading, UKDepartment of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62, Lund, SwedenClimate Research Division, Environment and Climate Change Canada, Victoria, BC, V8W 2Y2, CanadaCenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanClimate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstr. 5, 3012 Bern, SwitzerlandSchool of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UKNOAA/Geophysical Fluid Dynamics Laboratory (GFDL), 201 Forrestal Rd., Princeton, NJ 08540, USACenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanMeteorological Research Institute (MRI), Nagamine 1-1, Tsukuba, Ibaraki 305-0052, JapanImpacts on Agriculture, Forests, and Ecosystem Services Division, Centro Euro-Mediterraneo sui Cambiamenti Climatici, Via Augusto Imperatore 16, 73100 Lecce, ItalySchool of Chemistry, University of Bristol, Cantock's Close, Clifton, Bristol BS8 1TS, UKNational Centre for Earth Observation, University of Leicester, Leicester, LE1 7RH, UKDepartment of Biology Sciences, Institute of Environment Science, University of Quebec at Montreal, Montreal, QC H3C 3P8, CanadaSino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, ChinaCICERO Center for International Climate Research, Pb. 1129 Blindern, 0318 Oslo, NorwayObservatoire de Paris, Université PSL, Sorbonne Université, CNRS, LERMA, Paris, FranceDepartment of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology (MIT), Building 54-1312, Cambridge, MA 02139, USALaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceDepartment Geoscience, Environment & Society, Université Libre de Bruxelles, 1050-Brussels, BelgiumClimate and Ecosystem Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720, USACentre for Coastal Biogeochemistry, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, AustraliaTNO, Dep. of Climate Air & Sustainability, P.O. Box 80015, NL-3508-TA, Utrecht, the NetherlandsDepartment of Chemistry, University of California Irvine, 570 Rowland Hall, Irvine, CA 92697, USAInternational Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849, USAJoint Global Change Research Institute, Pacific Northwest National Lab, College Park, MD 20740, USADepartment of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20740, USAClimate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaDepartment of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, Svante Arrhenius väg 8, 106 91 Stockholm, SwedenInternational Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849, USACenter for Environmental Measurement and Analysis, National Institute for Environmental Studies (NIES), Onogawa16-2, Tsukuba, Ibaraki 305-8506, JapanStatistics Division, Food and Agriculture Organization of the United Nations (FAO), Viale delle Terme di Caracalla, 00153 Rome, ItalyFinnish Meteorological Institute, P.O. Box 503, 00101, Helsinki, FinlandLaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceDepartment of Physics, Imperial College London, London SW7 2AZ, UKSchool of Environmental Engineering, Technical University of Crete, Chania, GreeceDepartment of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USAKNMI, P.O. Box 201, 3730 AE, De Bilt, the NetherlandsVrije Universiteit Amsterdam, Department of Earth Sciences, Earth and Climate Cluster, VU Amsterdam, Amsterdam, the NetherlandsScripps Institution of Oceanography (SIO), University of California San Diego, La Jolla, CA 92093, USAEnvironment and Climate Change Canada, 4905, rue Dufferin, Toronto, CanadaDepartment of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, CanadaLaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USACenter for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, JapanDepartment of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62, Lund, SwedenDepartment of Geographical Sciences, University of Maryland, College Park, MD 20740, USALaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceLaboratoire des Sciences du Climat et de l'Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, FranceClimate and Ecosystem Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720, USACollege of Hydrology and Water Resources, Hohai University, Nanjing, 210098, ChinaDepartment of Earth, Atmospheric, Planetary Sciences, Department of Agronomy, Purdue University, West Lafayette, IN 47907, USA<p>Understanding and quantifying the global methane (<span class="inline-formula">CH<sub>4</sub></span>) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of <span class="inline-formula">CH<sub>4</sub></span> continue to increase, making <span class="inline-formula">CH<sub>4</sub></span> the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>). The relative importance of <span class="inline-formula">CH<sub>4</sub></span> compared to <span class="inline-formula">CO<sub>2</sub></span> depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping <span class="inline-formula">CH<sub>4</sub></span> sources and from the destruction of <span class="inline-formula">CH<sub>4</sub></span> by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).</p> <p><span id="page1564"/>For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> or <span class="inline-formula">∼</span> 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is 29 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> larger than our estimate for the previous decade (2000–2009), and 24 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> larger than the one reported in the previous budget for 2003–2012 (Saunois et al., 2016). Since 2012, global <span class="inline-formula">CH<sub>4</sub></span> emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30 % larger global emissions (737 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, range 594–881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (<span class="inline-formula">∼</span> 65 % of the global budget, <span class="inline-formula"><</span> 30<span class="inline-formula"><sup>∘</sup></span> N) compared to mid-latitudes (<span class="inline-formula">∼</span> 30 %, 30–60<span class="inline-formula"><sup>∘</sup></span> N) and high northern latitudes (<span class="inline-formula">∼</span> 4 %, 60–90<span class="inline-formula"><sup>∘</sup></span> N). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters.</p> <p>Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span> by 8 Tg <span class="inline-formula">CH<sub>4</sub></span> yr<span class="inline-formula"><sup>−1</sup></span>, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; (ii) further development of process-based models for inland-water emissions; (iii) intensification of methane observations at local scales (e.g., FLUXNET-<span class="inline-formula">CH<sub>4</sub></span> measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning.</p> <p>The data presented here can be downloaded from <a href="https://doi.org/10.18160/GCP-CH4-2019">https://doi.org/10.18160/GCP-CH4-2019</a> (Saunois et al., 2020) and from the Global Carbon Project.</p>https://essd.copernicus.org/articles/12/1561/2020/essd-12-1561-2020.pdf |