August 14, 2019

expert reaction to paper questioning whether US fracking could be a cause of the global methane spike

Research, published in Biogeosciences, reports that shale gas extraction through fracking may be responsible for increases in methane gas in the atmosphere. 

Prof Grant Allen, Professor of Atmospheric Physics, University of Manchester, said:

“Methane is the second-most important greenhouse gas after carbon dioxide.  There remains significant uncertainty in the potential explanations for methane’s observed rapid and worrying global rise since 2006.  This paper suggests that US fracking may be responsible for a large proportion of this observed rise but this claim is highly contentious in the academic community and further work is needed to constrain uncertainty before conclusions such as this can be robustly backed up.  Other published and credible explanations include a dominant role for biogenic (or natural) emissions from wetlands as a result of positive climate feedbacks – the warming feeds the warming.  Agriculture, wildfires, and waste are also all a part of the mix.  A wide range of different methane fluxes from different source types (e.g. fossil fuels, agriculture, wildfires and wetlands) can all simultaneously explain the observed trend in methane (and carbon isotopes of methane) within the limits of uncertainty in our knowledge of their carbon-isotopic fingerprints and estimates of total methane emitted from each source type.  Other work has also proposed a role for changing chemical sinks of methane in the atmosphere.  The jury is still out on the relative importance of all of these sources in explaining methane’s rise.

“However, this paper makes a very important point – some sources of methane are within our gift to control, other (natural sources) are not as easily targeted.  Controlling emissions from fracking, and fossil fuels in general, represents a potential policy quick fix to stemming the rise of methane still further.  If we can control the manmade methane emission sources that we can, then methane levels could yet be stabilised.  However, natural climate feedbacks could override this intervention in a warmer future if we do not also simultaneously control carbon dioxide emissions now.  A wholesale approach to reducing all controllable forms of greenhouse gas emissions is required to avoid this.”

Prof Peter Styles, Emeritus Professor of Applied and Environmental Geophysics, Keele University, said:

“While this is certainly an important and interesting proposition (it isn’t a result), NASA have already published a study in February: https://www.nasa.gov/feature/jpl/nasa-led-study-solves-a-methane-puzzle, which said very much the same thing and as far as I can see isn’t referenced here.

“This paper seeks to ‘prove’ this admittedly plausible conjecture with an impenetrable set of algebraic equations which are unlikely to raise much enthusiasm from readers.  The argument rests on the isotopic ratios of C13 to C12 which are decreasing and they suggest that Shale Gas which has been trapped away from oxidation may have a lower ratio than ‘natural’ gas (i.e. from conventional reservoirs), in disagreement as they admit with a very large study of isotopic ratios from a diverse range of methane sources by Sherwood et al (2017) https://www.earth-syst-sci-data.net/9/639/2017/

“They admit that:“Our analysis contains two major assumptions: (1) that methane emissions as a percentage of gas produced are the same for shale gas and conventional natural gas (Eqs. 9 and10); and (2) that emissions from oil have remained proportional to the global rate of oil production”

“These need further testing!

“My own opinion is that transporting any gas whether ‘natural’ or ‘shale’ over large distances is always a bad idea due to leaks in pipelines,  transfers etc. and that this only ‘offshores’ our or any other country’s environmental responsibilities.  We have little control over the environmental regulations, employment conditions and industrial protocols of some countries where we are happy to obtain gas either from pipelines (Russia) or liquefied natural gas, (sundry Countries).  If we or any other country feel that gas is an important component of our energy mix then it behoves us (them) to source it as close to home as possible, preferably from our own bailiwick under our hopefully carefully controlled conditions and with as little handling as possible and to accept our own environmental responsibilities for this.”

Prof Quentin Fisher, Professor of Petroleum Geoengineering, University of Leeds, said:

“I am deeply sceptical about the headline to this study.  The results are extremely sensitive to highly questionable assumptions regarding the isotopic composition of methane found in shale.  The arguments made by previous studies that increase in methane in the atmosphere is from biogenic sources, such as release from wetlands and agriculture or burning of biomass, seem far more convincing.

“It’s also the case that the study itself admits that even if the increased methane concentrations were from shale that they are not a direct result of the hydraulic fracturing process.  For example, the USA has an aging gas transportation network, which results in significant methane leakages.  There is no way that the results of this study should be taken as evidence that fracking in the UK will lead to a significant increase in methane emissions to the atmosphere.”

‘Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane?’ by Robert Howarth was published in Biogeosciences at 14:00 UK time on Wednesday 14 August 2019. 

DOI: 10.5194/bg-16-1-2019

Declared interests

Prof Grant Allen: “I hold NERC research funding to research the Global Methane problem, and hold BEIS and UN funding to study and quantify emissions from oil and gas infrastructure.”

Prof Peter Styles: “I have no interests to declare.”

Prof Quentin Fisher: “I conduct research and consultancy for the petroleum industry related to conventional reservoirs. I do not work on shale gas production for the petroleum industry. I believe my views on this are totally impartial and I have no financial gain to be made from supporting hydraulic fracturing.”