Is Global Spike in Methane Emissions Caused by Natural Gas Industry or Animal Agriculture?
Reconciling the Conflicting Views
Prof. Robert HowarthCornell University
Ithaca, NY, USA
The Methane Project at Cornell University
Carbon Dioxide
Methane
http://news.discovery.com/earth/alas
kas-arctic-tundra-feeling-the-
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1.5 oC threshold
2.0 oC threshold
Shindell et al. 2012, Science
12 years from now
28 years from now
Total 550
Total natural 215Geological seeps ~ 0 (<< 15)
Wetlands & other biogenic 215
Total anthropogenic 335Natural gas & oil 132Coal 33Animal agriculture 65Rice 25Landfills & sewage 55Biomass burning 25
Revised estimates for global methane emissions (Tg/yr)
1995 – 2000
Modified & updated from Begon et al. 2014 Essentials of Ecology
Revised downward due to 14C data in ice-core bubbles(Petrenko et al. 2017 Nature 548, 443–446
Revised upward, since 30% of atmospheric methane in 1995 was “14C-dead” (Lassey et al. 2007)
Hansen et al. (2016) Young People’s Burden: Requirement of Negative CO2 Emissions
Two major schools of thought on cause of methane spike over past decades:
Increase flux from animal agriculture (particularly cows & cattle)Shale gas & oil emissions (North America)
Corresponds to global increase in flux of 20 Tg/yr
0
5
10
15
20
25
30
35
1980 1990 2000 2010 2020 2030 2040
Exaj
ou
les
Natural Gas Production in the United StatesDept of Energy -- EIA 2015 Outlook data and mean reference projections
conventional
shale
Howarth 2015
Schneising et al. (2014) –“Remote sensing of fugitive methane emissions from oil and gas production in North American tight geologic formations.” Earth’s Future 2: 548-558
global
United States
north pole
south pole
equator
0 5 10 15 20
Pei
sch
l et
al. (
20
15
)
NE Marcellus
Fayetteville
Western Arkoma
Haynesville
Schneising et al. (2014)Bakken & Eagle Ford
Caulton et al. (2014)SW Marcellus
Petron et al. (2014)
Denver-Julesburg
Allen et al. (2013)US Average
Karion et al. (2013)Uinta
Petron et al. (2012)Denver-Julesburg
EPA (2013)
EPA (2011)
Howarth et al. (2011)
Methane emissions from unconventional gas operations (upstream only, % of production)
Upstream methane emissions shale and other unconventional gas
Based on Howarth 2015
What about several prominent 2016 studies that use 13C content of methane?
Schaefer H, et al. (2016) A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by ¹³CH4. Science 352(6281): 80–84.
Rice A, et al. (2016) Atmospheric methane isotopic record favors fossilsources flat in 1980s and 1990s with recent increase. PNAS doi/10.1073/pnas.1522923113
Schwietzke S, et al. (2016) Upward revision of global fossil fuel methaneemissions based on isotopic database. Nature 538: 88-91.
Atmosphere-47‰
Microbial sources Fossil Fuels
13C content of methane
Diagram adapted from Chanton et al. (2005)
Biomass burning
Fewer cows and cattle in US in recent decades, so unlikely to be cause of increased methane
Atmosphere-47‰
Microbial sources Fossil Fuels
13C content of methane
Biomass burning
Shale gas (fracking)Golding et al. (2013)
Golding S. et al. 2013. Stable isotope geochemistry of coal bed and shale gas and related production waters: A review. International Journal of Coal Geology 120: 24-40.
Total 550
Total natural 215Geological seeps ~ 0 (<< 15)
Wetlands & other biogenic 215
Total anthropogenic 335Natural gas & oil 132Coal 33Animal agriculture 65Rice 25Landfills & sewage 55Biomass burning 25
Revised estimates for global methane emissions (Tg/yr)
152
1995 – 2000 2015
355
570
Modified & updated from Begon et al. 2014
A call for making new measurements of 14C in methane in today’s atmosphere.
Far less ambiguity than for 13C in teasing apart fossil fuel emissions from cows and other biogenic emissions.
Shale Gas Coal
Atmosphere
Combustion &Biomass Burning
Sewage &Liquid WasteBogs
Fens
Tropical Wetlands
RiceAnimals
Landfills
ConventionalNatural Gas
Based on Chanton et al. 2005, Lassey et al. 2007, and Golding et al. 2013
Shale Gas Coal
Atmosphere
Combustion &Biomass Burning
Sewage &Liquid WasteBogs
Fens
Tropical Wetlands
RiceAnimals
Landfills
ConventionalNatural Gas
Based on Chanton et al. 2005, Lassey et al. 2007, and Golding et al. 2013
Increase to 33%, if from shale gas
Decrease to 29%, if from cows
An urgent call to measure 14C in current atmospheric methane.
http://www.world-nuclear.org/getmedia/1b6ed77e-3853-4b9e-9835-048cc4dce475/nuclear-electricity-production.png.aspx
Nuclear plants produce 14C methane, but likely to be the same in 1995-2000 as in 2015, since nuclear power production globally is similar.
Questions?
Prof. Robert HowarthCornell University
Ithaca, NY, [email protected]
More information: www.howarthlab.orgFunding: the Park Foundation and an endowment given by David R. Atkinson
to Cornell University.
The Methane Project at Cornell University
