PKU-LSCE winter shool, 14 October 2014 Global methane budget : The period Philippe Bousquet 1, Robin Locatelli 1, Shushi Peng 1, and Marielle Saunois 1 1 LSCE-CEA-UVSQ-CNRS, IPSL France, GEO CARBON

PKU-LSCE winter shool, 14 October 2014 Atmospheric methane is … different than carbon dioxide ITEMCO 2 CH 4 Surface mixing ratio (MLO, Max 2013)400 ppm1860 ppb Land / ocean fluxesbothmostly land Anthrop. Emissions~ 10 PgC~ 330 TgC Proportion of anthrop. emissions~ 15%~ 60% Major anthrop. emissions/processFF combustion, LUCLivestock, FF, landfills & waste, rice, BBG,.. Major natural emissions/processRespirationWetlands, fresh waters, Earth leaks, termites,.. Major sinks/processPhotosynthesisAtm. Chem., soil dep. Global balanceWell constrained (atm. obs.)Not well constrained (OH) Radiative forcing~ 1.8 W/m 2 ~ 0.5 W/m 2 (conc) Global Warming Potential134 (100yr), 86 (20yr) Atmospheric Lifetimecenturydecade Mitigation potentialLowerHigher OthersOzone precursor

PKU-LSCE winter shool, 14 October 2014 Outline 2010 Budget Inter-annual variability (IAV) of emissions Trends

PKU-LSCE winter shool, 14 October 2014 Inversions performed Variational system (PYVAR-LMDZ-SACS) 3 versions of the LMDZ model (different PBL schemes & different convection schemes) : LMDZ-TD, LMDZ-SP, LMDZ-NP 3 set of observations : surface background (BG), surface extended (EXT), satellite (GOSAT) Time period (surface), (GOSAT-LEIcester) Locatelli, PhD

PKU-LSCE winter shool, 14 October methane budget Locatelli, PhD Blackline: former inversion Red line : prior flux Red Bar : global flux (right scale) Blue bar : regional flux (left scale) -Global emissions : 534 Tg/yr -Range = [ ] -Chinese emissions reduced compared to the prior and to a former inversion (EDGAR42) : 68 Tg/yr compared to 80 Tg/yr (-16%) EPA=44, EDGAR=80 -1 inversion only gives a total above the prior in China (LMDZ- NP with extended network) -S. Am. Trop flux consistently larger than former inversion -Africa : stay close to the prior in both present and former inv. Important influence of transport at regional scale !

PKU-LSCE winter shool, 14 October 2014 IAV of emissions : global & hemispheric scale Locatelli, PhD 2 large anomalies : : Tropics + High Nlats : Tropics + Mid Nlats Larger emission changes in when using satellite data

PKU-LSCE winter shool, 14 October 2014 IAV of emissions : Regional & country scales Locatelli, PhD Robust and fast changes in Tropical South America end 2009 with positive trend Less robust changes in South east Asia & China (more transport dependant)

PKU-LSCE winter shool, 14 October 2014 IAV of emissions : Link with ENSO Locatelli, PhD

PKU-LSCE winter shool, 14 October 2014 IAV of emissions : Link with ENSO Locatelli, PhD

PKU-LSCE winter shool, 14 October 2014 IAV of emissions : comparaison with ORCHIDEE 2 versions of ORCHIDEE : old version (blue), new version (red) Goog agreement at global scale, Phasing differences in South America Locatelli, PhD; S. Peng, pers. comm GLOBAL Tropical South America

PKU-LSCE winter shool, 14 October 2014 Trends of emissions : Tg/yr 2 at global scale +1.9 Tg/yr 2 from the tropics +0.9 Tg/yr 2 from China 1/3 of EDGAR trend 2 times EPA trend +0.6 Tg/yr 2 in Trop. south Am. Not consistent with ORCHIDEE wetl. model -0.3 Tg/yr 2 from North America temperate Negative trend in ORCHIDEE model but large IAV Locatelli, PhD ; S. Peng pers. Comm.

PKU-LSCE winter shool, 14 October 2014 Paths to uncertainty reduction in the methane cycle Large uncertainties in natural wetland emissions ---> Improved parametrisations, remote sensed flooded areas, WETCHIMP-II Other natural emissions are also highly uncertain (geological, fresh waters) ---> proxy tracers, field measurements Emission partition in space and time with atmospheric inversions ---> Use of isotopes, other proxy tracers (e.g. ethane), improved inventories Regionalisation of methane fluxes using inversions has to be improved ---> Satellite data, continuous measurements Large uncertainties in the OH mean values (less on IAV after 2000) ---> proxy methods & isotopes Uncertainty on transport modelling is significant ---> Refine models, Use/Compare models (TRANSCOM) Global methane budget needs consolidation ---> Produce regular updates through Global Carbon Project (GCP)

PKU-LSCE winter shool, 14 October 2014 Additionnal slides

PKU-LSCE winter shool, 14 October 2014 Atmospheric methane is important because … After carbon dioxide (CO 2 ), methane (CH 4 ) is the second most important well-mixed greenhouse gas contributing to human- induced climate change. In a time horizon of 100 years, CH 4 has a Global Warming Potential >30 times larger than CO 2. It is responsible for 20% of the global warming produced by all well-mixed greenhouse gases. The concentration of CH 4 in the atmosphere is above 150% from the levels prior to the Industrial Era (cf. 1750). The atmospheric life time of CH 4 is approximate 10±2 years making it a good target for Climate change mitigation Methane also contributes to ozone production in the troposphere, which is a pollutant with negative impacts on human health and ecosystems. Increasing emissions of methane are transformed into water in the stratosphere by chemical reactions. Updated to 2012 Kirschke et al. 2013, IPCC 2013 ; Voulgarakis et al., 2013

PKU-LSCE winter shool, 14 October ppb ‰ Observations ~ -0.04‰/yr ~ +5.3 ppb/yr 1-box model for CH 4 and 13 CH 4 : Observations DIFFERENCE (Tg/yr) ( )–( )

PKU-LSCE winter shool, 14 October box model, 2 equations for mass conservation of CH 4 and 13 CH 4 3 emission types, one sink : Anthropogenic, prior : 280 to 350 Tg/yr, to -51.3‰ (IAV from EDGAR4.2), or flat with time. Natural, prior : 180 Tg/yr, -60‰, No IAV Biomass & biofuel Burning, prior : 35 Tg/yr, -20‰, No IAV Sink, prior : 540 Tg/yr, IAV from atmospheric concentrations Annual optimization for the period Larger relative prior errors on emissions than on isotopic signatures and total sink 1-box model for CH 4 and 13 CH 4 : Setup

PKU-LSCE winter shool, 14 October ppb ‰ Observations Optimized model Prior model ~ -0.04‰/yr ~ +5.3 ppb/yr DIFFERENCE (Tg/yr) ( )–( ) 1-box model for CH 4 and 13 CH 4 : Observations

PKU-LSCE winter shool, 14 October 2014 Anthopogenic emissions (-52‰) Natural emissions (-60‰) Biomass Burning (-20‰) Chemical sink (KIE -5‰) DIFFERENCE (Tg/yr) ( )–( ) Anthrop Natural BBG Chem. loss PriorEDGARFLAT anthrop Anthrop 103 Natural 2023 BBG -20 Chem loss -4-2 TOTAL 24 Prior = EDGAR 1-box model for CH 4 and 13 CH 4 : Fluxes

PKU-LSCE winter shool, 14 October 2014 Anthopogenic emissions (-52‰) Natural emissions (-60‰) Biomass Burning (-20‰) Chemical sink (KIE -5‰) Anthrop Natural BBG Chem. loss EDGAR4.2 : Increase of coal emissions of +60% 1-Box model : Increase of coal emissions Of ~ 20 % Between 2000 and 2008 : 1-box model for CH 4 and 13 CH 4 : Fluxes