“Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane?”

This article to which we offer the Full-Article Link , is published with Creative Commons licensing.  It’s findings may impact many aspects of human life in the near-term, and as such, is worth both the layman’s and the scientist’s appraisal.

In a very small and not all-inclusive nutshell, its conclusions indicate that the past decade’s increase in human-mediated methane emissions – a most ‘pernicious’ form of greenhouse gas – may arise not from cow or pig, or meat production, or any direct form of agriculture, but from shale gas.

Screen Shot 2019-08-16 at 7.59.23 AMA schematic of human production of conventional and shale gas.  Conventional gas migrates from the shale through semipermeable sandstone and other layers over time.  We know of shale gas as a result of hydrolytic fracking and horizontal drilling.

Biogeosciences, 16, 3033–3046, 2019 doi
© Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License.

Robert W. Howarth, Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA Correspondence: Robert W. Howarth (howarth@cornell.edu)
Received: 10 April 2019 – Discussion started: 23 April 2019
Revised: 11 July 2019 – Accepted: 12 July 2019 – Published: 14 August 2019


“Methane has been rising rapidly in the atmosphere over the past decade, contributing to global climate change. Unlike the late 20th century when the rise in atmospheric methane was accompanied by an enrichment in the heav- ier carbon stable isotope (13C) of methane, methane in re- cent years has become more depleted in 13C. This depletion has been widely interpreted as indicating a primarily bio- genic source for the increased methane. Here we show that part of the change may instead be associated with emissions from shale-gas and shale-oil development. Previous studies have not explicitly considered shale gas, even though most of the increase in natural gas production globally over the past decade is from shale gas. The methane in shale gas is somewhat depleted in 13C relative to conventional natural gas. Correcting earlier analyses for this difference, we conclude that shale-gas production in North America over the past decade may have contributed more than half of all of the increased emissions from fossil fuels globally and approximately one-third of the total increased emissions from all sources globally over the past decade.”



“We conclude that increased methane emissions from fossil fuels likely exceed those from biogenic sources over the past decade (since 2007). The increase in emissions from shale gas (perhaps in combination with those from shale oil) makes up more than half of the total increased fossil-fuel emissions. That is, the commercialization of shale gas and oil in the 21st century has dramatically increased global methane emissions.

Note that while methane emissions are often referred to as “leaks”, some of the emissions include purposeful venting, including the release of gas during the flowback period immediately following hydraulic fracturing, the rapid release of gas from blowdowns during emergencies but also for routine maintenance on pipelines and compressor stations (Fig. 4a), and the steadier but more subtle release of gas from storage tanks (Fig. 4b) and compressor stations to safely maintain pressures (Howarth et al., 2011). This suggests large oppor- tunities for reducing emissions, but at what cost? Do large capital investments for rebuilding natural gas infrastructure make economic sense, or would it be better to move towards phasing natural gas out as an energy source and instead invest in a 21st-century energy infrastructure that embraces renewable energy and much more efficient heat and transportation through electrification (Jacobson et al., 2013)?

In October 2018, the Intergovernmental Panel on Climate Change issued a special report, responding to the call of the United Nations COP21 negotiations to keep the planet well below 2.0C of the pre-industrial baseline (IPCC, 2018). They noted the need to reduce both carbon dioxide and methane emissions, and they recognized that the climate system re- sponds more quickly to methane: reducing methane emis- sions offers one of the best routes for immediately slowing the rate of global warming (Shindell et al., 2012). Given our finding that natural gas (both shale gas and conventional gas) is responsible for much of the recent increases in methane emissions, we suggest that the best strategy is to move as quickly as possible away from natural gas, reducing both carbon dioxide and methane emissions. Natural gas is not a bridge fuel (Howarth, 2014).

Finally, in addition to contributing to climate change, methane emissions lead to increased ground-level ozone lev- els, with significant damage to public health and agriculture. Based on the social cost of methane emissions of USD 2700 to USD 6000 per ton (Shindell, 2015), our baseline estimate for increased emissions from shale gas of 9.4 Tg per year cor- responds to damage to public health, agriculture, and the climate of USD 25 billion to USD 55 billion per year for each of the past several years. This is comparable to the wholesale value for this shale gas over these years.”


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