September 29, 2017

expert reaction to paper on methane from agriculture

A new study, published in Carbon Balance and Management, provides revised estimates of methane emissions and carbon fluxes for global livestock that facilitate the development and evaluation of earth system models and environmental assessments.

Prof. Piers Forster, Director of the Priestley International Centre for Climate at the University of Leeds, said:

“Livestock are the largest source of methane emissions and this useful revision will increase our estimate of human-induced emissions from all sources (around 330 Tg per year) by 4%. This upwards revision coupled to new work from the University of Reading* that increased our estimate of the warming effect of methane by 25% shows that methane is playing a considerably larger role in climate change than we thought a year ago.”

* Etminan, M., G. Myhre, E. J. Highwood, and K. P. Shine (2016), Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing, Geophys. Res. Lett., 43, 12,614–12,623, doi:10.1002/2016GL071930.

Prof. Dave Reay, Professor of Carbon Management at the University of Edinburgh, said:

“This is a useful study in terms of highlighting global methane emissions from livestock. It’s good to see an update of  the estimates of how much comes from the animals themselves and how much from the manure they produce. The total estimate appears a bit higher than previous ones, though the uncertainties are too high to say whether there is any definite increase.

“As our diets become more meat and dairy-rich, so the hidden climate change cost of our food tends to mount up. There are a host of ways to cut these emissions, including everything from different cattle feeds and improved welfare, to avoiding over-consumption and waste. Cows belching less methane may not be as eye-catching as wind turbines and solar panels, but they are just as vital for addressing climate change.”

Prof. Bill Collins, Professor of Climate Processes, University of Reading, said:

“If this study is right it will be harder to achieve the Paris climate goals. Agriculture is the largest single source of methane human activity contributes to the atmosphere, making up more than a third of the total “man-made” methane emissions. If we wish to limit temperature rises to below 2 or even 1.5 degrees we will need to drastically reduce methane emissions as well as CO2. Methane emissions from non-agricultural sources can be reduced through technical measures or reductions in fossil fuel use, however agricultural emissions are far less easy to control and are likely to increase as the world’s population grows and consumes more food (especially beef). If the methane emissions from livestock are indeed currently underestimated, then even larger reductions in CO2 emissions will be needed to have a chance of keep temperatures below dangerous levels.”

* ‘Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock’ by Wolf et al. will be published in Carbon Balance and Management at on Friday 29 September. 

Declared interests

None received.