Presentation by Marielle Saunois at the 2nd ICOS Science Conference in Helsinki, Finland, 27-29 Sep 2016.

1. Changes in the global methane budget since 2000
Marielle Saunois1, Philippe Bousquet1, Ben Poulter2, Anna Peregon1, Philippe Ciais1, Josep G. Canadell3, Edward J.
Dlugokencky4, Giuseppe Etiope5, David Bastviken6, Sander Houweling7,8, Greet Janssens-Maenhout9, Francesco N.
Tubiello10, Simona Castaldi11,12, Robert B. Jackson13, Mihai Alexe9, Vivek K. Arora14, David J. Beerling15, Peter Bergamaschi9,
Donald R. Blake16, Gordon Brailsford17, Victor Brovkin18, Lori Bruhwiler4, Cyril Crevoisier19, Patrick Crill20, Kristofer Covey21,
Charles Curry212, Christian Frankenberg223, Nicola Gedney234, Lena Höglund-Isaksson254, Misa Ishizawa256, Akihiko Ito256,
Fortunat Joos267, Heon-Sook Kim256, Thomas Kleinen18, Paul Krummel278, Jean-François Lamarque289, Ray Langenfelds278,
Robin Locatelli1, Toshinobu Machida256, Shamil Maksyutov256, Kyle C. McDonald2930, Julia Marshall301, Joe R. Melton312, Isamu
Morino254, Vaishali Naik33, Simon O’Doherty324, Frans-Jan W. Parmentier335, Prabir K. Patra346, Changhui Peng357, Shushi
Peng1, Glen P. Peters368, Isabelle Pison1, Catherine Prigent397, Ronald Prinn3408, Michel Ramonet1, William J. Riley3941, Makoto
Saito256, Monia Santini12, Ronny Schroeder2930,402, Isobel J. Simpson16, Renato Spahni267, Paul Steele278, Atsushi Takizawa413,
Brett F. Thornton20, Hanqin Tian424, Yasunori Tohjima256, Nicolas Viovy1, Apostolos Voulgarakis453,, Michiel van Weele464,
Guido R. van der Werf475, Ray Weiss486, Christine Wiedinmyer298, David J. Wilton15, Andy Wiltshire497, Doug Worthy5048, Debra
Wunch5149, Xiyan Xu4139, Yukio Yoshida265, Bowen Zhang442, Zhen Zhang2,520, and Qiuan Zhu531.

2. Global Carbon Project - methane
• Objectives :
• Stimulate research and projects on the global to regional methane
budget and its evolution since pre-industrial times
• Produce and publish regular updates of the global methane budget
• How ?
• Constitution of a GCP-CH4 group of scientists interested by the
objectives : observations, inventories, wetland models, CTMs, inversions
• Regular exchanges during the year (teleconf, side events in existing
meetings, …)
• Who ?
• Any individual scientist, team, or thematic group working on the global to
regional scales of the methane cycle, bottom-up/top-down,
experimentalist/modeler …

3. Methane Budget releases
Kirschke et al., 2013: The Global Methane Budget: 1980-2009
Saunois et al., 2016: The Global Methane Budget: 2000-2012

4. Atmospheric
Observations
Atmospheric
chemistry (OH)
Biogeochemistry
Models
(B‐U)
Emission
Inventories
(B‐U)
Inverse Models
(T‐D)
Ground‐based
data from
observation
networks (AGAGE,
CSIRO, NOAA,
UCI, LSCE, others).
Satellite data
(SCIAMACHY,
GOSAT)
Ensemble of 11
wetland models,
following the
WETCHIMP
intercomparison
Model for Termites
emissions
Other sources
from literature
From Kirschke et
al., (2013) Long‐
term trends and
decadal variability
of the OH sink.
ACCMIP CTMs
intercomparison.
Coming in 2016 :
CCMI runs for OH
The Tools and Data
Agriculture and
waste related
emissions, fossil
fuel emissions
(EDGAR4.2, EPA,
IIASA, FAO).
Fire emissions
(GFED3 & 4s,
FINN, GFAS, FAO).
Biofuel estimates
Suite of different 8
atmospheric
inversion models
(TM5‐4DVAR (x2),
LMDZ (x2),
CarbonTracker‐
CH4, GELCA, ACTM,
TM3, NIESTM).
Ensemble of 30
inversions
(different obs &
setup)
Suite of different 8
atmospheric
inversion models
(TM5‐4DVAR (JRC
& SRON), LMDZ‐
MIOP, PYVAR‐
LMDz
CarbonTracker‐
CH4, GELCA, ACTM,
TM3, NIESTM).
Ensemble of 30
inversions
(different obs &
setup)

5. Fresh waters 122 [100%]
Wild animals 10 [100%]
Wild fires 3 [100%]
Termites 9 [120%]
Geological 52 [50%]
Oceans 2 [100%]
Permafrost 1 [100%]
Global methane budget 2003-2012 (TgCH4/yr)
Natural wetlands
Other natural emissions
Biomass & biofuel burning
Coal, oil & gas exploitation
Agriculture & waste
Bottom-up Top-down
167 [80%]185 [40%]
Atmospheric-based budget
(Top-down inversions)
558 TgCH4/yr [5%]
Process-based budget
(Bottom-up models & inventories)
736 TgCH4/yr [25%] Mean [min max range in %]
64 [150%]199 [90%]
34 [54%]30 [30%]
105 [50%]121 [20%]
188 [64%]195 [15%]
Coal 41 [80%]
Gas & oil 79 [10%]
Rice 30 [10%]
Enteric ferm & manure 106[20%]
Landfills & waste 59 [20%]
Saunois et al., 2016
ESSD
Key message: main uncertainties are due to inland water emissions

6. Global methane budget 2003-2012 (TgCH4/yr)
http://lsce-datavisgroup.github.io/MethaneBudget/
Interactive data visualisation of the methane budget on:

7. Global emission changes (TD)
Global mixing ratio
• Sustained increase since 2006
• Reached 1810 ppb in 2012
1838 ppb in June 2016
Growth rate
• 2000‐2006: 0.6±0.1 ppb/yr
• 2007‐2012: 5.5±0.6 ppb/yr
• 2014: 12.5 ±0.5 ppb/yr
• 2015: 10.1 ±0.7 ppb/yr
Global inverted annual emissions
• Stable from 2000 to 2006
• Stable from 2007 onward
• « abrupt change » in 2006‐2007?
2000 2002 2004 2006 2008 2010 2012Saunois et al. In prep

8. Years
2002 2006 2010 2002 2006 2010
2002 2006 2010
-40
-20
0
20
40 Global total sources
-10
0
10
20 Mid-latitude total sources
Tropical total sources
Boreal total sources
Years
Methaneemissionanomaly(Tg/yr)
2002 2006 2010
-40
-20
0
20
40 Global total sources
-20
-10
0
10
20 Mid-latitude total sources
2002 2006 2010
-40
-20
0
20
40 Global anthropogenic sources
Tropical total sources
Boreal total sources
2002 2006 2010
Global natural sources
Global emission changes (TD)
Saunois et al. In prep
• Global anomaly mainly from the
tropics
• IAV in the tropics: ± 15Tg CH4.yr‐1
• Mid latitudes anomaly < 5 TgCH4.yr‐1
• Small contribution from boreal
regions
• 2000-2006:
Natural source anomaly enhanced
by a positive trend from
anthropogenic emissions
• 2007 onward:
Rather stable natural and
anthropogenic sources
• No significant trend in natural
(wetland) sources (BU and TD)
• Increasing anthropogenic
emissions but not as large as in
BU Methaneemissionanomaly(Tg/yr)
BU BU
=> Changes between 2002-2006 and 2008-2012

9. 2004‐2010 difference: a geographic view
T‐D inversions :
• A +17 [8‐32] TgCH4.yr‐1 global
emission increase
• Mostly tropical (80%)
• Main regional contributors :
South America, Africa, China
• Non‐significant contributions
from Europe, North America or
high latitudes
T‐D Positive anomaly T‐D Negative anomaly
B‐U neutral
Saunois et al. In prep
B‐U Positive anomaly B‐U Negative anomaly
T‐D neutral
2008-2012 minus 2002-2006
B‐U models & inventories :
• A 32 Tg CH4 yr‐1 emission anomaly
• Mostly mid‐latitudes (50%)
• Dominant contribution of China
TD
BU

10. 2004‐2010 difference: a process view
T‐D inversions :
• Similar positive contributions of
agricult. & waste, fossil fuel
• Smaller positive constribution of
wetlands
• Negative contribution of biomass
burning
2008-2012 minus 2002-2006
T‐D Positive anomaly T‐D Negative anomaly
B‐U neutral
Saunois et al. In prep
B‐U Positive anomaly B‐U Negative anomaly
T‐D neutral
TD
BU
Key points: agriwaste (+) and bbg (-) anomalies
are consistent between TD and BU
30
20
10
0
-10
Emissiondifferences(Tg.yr-1)
Wetlands
Others
Agri-waste
Biomass burning
Fossil fuels
B‐U models & inventories :
• Dominant positive contribution of
fossil fuels and agriculture and
waste.
• No contribution from wetlands
• Negative contribution of biomass
burning

11. Hausmann et al. (2016), based on ethane/methane ratio, over 2007-2014:
• +24-45 Tg CH4 yr-1 increase in global methane emissions
• at least 39% from oil and gas emissions (ref scenario)
• => 9-18 Tg CH4 yr-1 increase from oil and gas emissions
Recent methane increase: toward a consensus on a scenario?
Our study, based on TD results, 2012-2008 minus 2002-2006 difference:
• +17 [8-32] Tg CH4 yr-1 increase in global methane emissions
• +8 [0-16] Tg CH4 yr-1 increase in fossil fuel related methane emissions
Key message :
- agreement with Hausmann et al. (2016) though likely in their lower range

12. Sources
Emission changes
(Tg CH4.yr-1)
Isotopic signatures
(0/00)
Schaefer et al. (2016)
2007-2014 period
19.7 -59 [-56 to -61]
Sources
Emission changes
(Tg CH4.yr-1)
Isotopic signatures
(0/00)
Schaefer et al. (2016)
2007-2014 period
19.7 -59 [-56 to -61]
Wetlands +5 [-4-11]
Agriculture & Waste +10 [9-12]
Fossil fuels +8 [0-16]
Biomass burning -4 [-9-0]
Others
Total 19
Sources
Emission changes
(Tg CH4.yr-1)
Isotopic signatures
(0/00)
Schaefer et al. (2016)
2007-2014 period
19.7 -59 [-56 to -61]
Quay et al. (1991)
Wetlands +5 [-4-11] -55
Agriculture & Waste +10 [9-12] -55
Fossil fuels +8 [0-16] -40
Biomass burning -4 [-9-0] -20
Others
Total 19 -56
Recent methane increase: toward a consensus on a scenario?
Key messages :
- agreement with Schaefer et al. (2016) on the recent change
- mainly biogenic (more agriculture & waste than wetlands)
- fossil fuel emission increase balanced by a decrease in biomass burning emissions
Sources
Emission changes
(Tg CH4.yr-1)
Isotopic signatures
(0/00)
Schaefer et al. (2016)
2007-2014 period
19.7 -59 [-56 to -61]
Quay et al. (1991) Schaefer et al. (2016)
Wetlands +5 [-4-11] -55 -60
Agriculture & Waste +10 [9-12] -55 -60
Fossil fuels +8 [0-16] -40 -37
Biomass burning -4 [-9-0] -20 -22
Others
Total 19 -56 -58
Sources
Emission changes
(Tg CH4.yr-1)
Isotopic signatures
(0/00)
Schaefer et al. (2016)
2007-2014 period
19.7 -59 [-56 to -61]
Quay et al. (1991) Schaefer et al. (2016)
Wetlands +5 [-4-11] -55 -60
Agriculture & Waste +10 [9-12] -55 -60
Fossil fuels +8 [0-16] -40 -37
Biomass burning -4 [-9-0] -20 -22
Others 1-3 -63 (termites) to -42 (oceanic sources)
Total 19 -56 -58
Total 20-23 -62 to -59

13. Take-home messages
• Methane global emissions are 558 TgCH4 yr‐1 [540‐570] for 2003‐2012 as inferred by an
ensemble of T‐D inversions
• B‐U infer much larger global totals because of larger natural emissions. More work is
needed especially for inland water emissions
• The 2004 to 2010 change in methane emissions is estimated at 17 Tg CH4 yr‐1 [8‐32] for T‐
D inversions and 29 Tg CH4 yr‐1 [13‐38] for B‐U models and inventories but ranges remain
large.
• Poor agreement on the latitudes or processes responsible for the increase :
• More tropical and biogenic dominated for T‐D
• More mid‐latitudes and fossil‐fuel dominated for B‐U
• Current most likely scenario for the 2004 to 2010 increase in methane emissions:
dominance of agriculture and waste with a contribution of 1/ wetlands and 2/ fossil fuels
compensated by a decrease in BBG (compliant with both 13C and ethane based studies)

14. Thank you for your attention
Global Methane Budget Website
http://www.globalcarbonproject.org/methanebudget
Activity Contacts E-mail
Philippe Bousquet philippe.bousquet@lsce.ipsl.fr
Pep Canadell pep.canadell@csiro.au
Marielle Saunois Marielle.saunois@lsce.ipsl.fr
Anna Peregon anna.peregon@lsce.ipsl.fr

15. Atmospheric
Observations
Atmospheric
chemistry (OH)
Biogeochemistry
Models
(B‐U)
Emission
Inventories
(B‐U)
Inverse Models
(T‐D)
Ground‐based
data from
observation
networks (AGAGE,
CSIRO, NOAA,
UCI, LSCE, others).
Satellite data
(SCIAMACHY,
GOSAT)
Ensemble of 11
wetland models,
following the
WETCHIMP
intercomparison
Model for Termites
emissions
Other sources
from literature
From Kirschke et
al., (2013) Long‐
term trends and
decadal variability
of the OH sink.
ACCMIP CTMs
intercomparison.
Coming in 2016 :
CCMI runs for OH
The Tools and Data
Agriculture and
waste related
emissions, fossil
fuel emissions
(EDGAR4.2, EPA,
IIASA, FAO).
Fire emissions
(GFED3 & 4s,
FINN, GFAS, FAO).
Biofuel estimates
Suite of different 8
atmospheric
inversion models
(TM5‐4DVAR (x2),
LMDZ (x2),
CarbonTracker‐
CH4, GELCA, ACTM,
TM3, NIESTM).
Ensemble of 30
inversions
(different obs &
setup)
Suite of different 8
atmospheric
inversion models
(TM5‐4DVAR (JRC
& SRON), LMDZ‐
MIOP, PYVAR‐
LMDz
CarbonTracker‐
CH4, GELCA, ACTM,
TM3, NIESTM).
Ensemble of 30
inversions
(different obs &
setup)

16. Wetland emissions from B-U
Poulter et al., in review, Nature CC
• 11 process models forced with the same wetland extent : merging of remote sensing based
observations of daily inundation from the Surface WAter Microwave Product Series Version
2.0 (SWAMPS; Schroeder et al., 2015) with the static inventory of wetland area from the
Global Lakes and Wetlands Database (GLWD; Lehner and Doll 2004),
• 184 Tg/yr emissions on average for 2000‐2012 (range [152‐222])
(Tian et al. 2010)
(Ringeval et al. 2010)
(Hopcroft et al. 2011)
Key messages: 1) No trend in wetland emissions between 2000 and 2012
2) Differences in wetland extent represent 30-40% of the previously estimated
range of wetland emissions

17. Regional methane budget (TD) (2003-2012 decade)
Saunois et al., 2016
Prior
Posterior• Largest emissions in
Tropical South America,
South-East Asia and China
• Chinese emissions
significanlty lower than the
prior value (mostly given
byEDGAR4.2 inventory)
• African emissions
significantly larger than the
prior value (mostly given
by EDGAR4.2 & GFED
inventory)
Key message: Three regions represent 50% of emissions (Trop. S America,
South East Asia, China) : reduced emissions in China compared to EDGARv42