Column flawed on methane impact

I AM very grateful to Mr Anton Coaker for inviting me in his latest column for the Western Morning News (23rd September) to explain why his reasoning that ‘cattle burps’ have no effect on the concentration of methane in the atmosphere and make no contribution to global warming is seriously flawed from a scientific standpoint. Indeed, it is a pleasure to do so.

There are three main points on which Mr Coaker is simply wrong in what he writes. Firstly, although as he writes, methane (CH4) exists in the atmosphere for a much shorter time after being emitted (around 12 years) than carbon dioxide (CO2), it has a very powerful effect before it breaks down and therefore cannot be ignored.

The Intergovernmental Panel on Climate Change demonstrates that the global warming potential of a unit mass of CH4 is more than 80 times that of CO2 over a 20-year period, and between 28 and 36 times when considered in the timeframe of 100 years. Since 1750, CH4 concentrations in the atmosphere have increased by 2.6 times, and the effect of this gas is calculated to have contributed at least a fifth of recent global warming. CH4 is thus considered the second most important greenhouse gas as far as global warming is concerned.

Secondly, Mr Coaker suggests the number of domestic cows is fairly static and ‘cow-burp’ methane can’t be much different today than what it was ten or 100 years ago. A 2019 House of Commons Library document (https:// researchbriefings.files.parliament. uk/documents/SN03339/SN03339. pdf ) shows for the UK that the number of cattle rose from 6 million in 1875 to over 15 million in 1974 and thereafter fell to the presentday figure of around 10 million, which is not an historical trend that can be described as ‘fairly static’. Furthermore, methane in the atmosphere reflects not just what is happening in the UK but also what happens worldwide, and globally cattle meat production has more than doubled since 1961 (https://ourworldindata.org/ meat-production). Studies in the peer-reviewed scientific literature (e.g. https://academic.oup.com/ af/article/9/1/69/5173494) have concluded animal emissions are a significant factor in rising global CH4 emissions. The UN Food and Agriculture Organisation reports total livestock emissions account for 14.5 per cent of all human-produced greenhouse gas emissions, with CH4 making up 44 per cent of this figure.

Thirdly, the notion which Mr Coaker promotes that all farmers are doing today ‘is to redirect and manage a natural cycle’ of CH4 has no evidence to support it. Today, there are 3.5 billion domesticated ruminants on the planet compared with only 75 million non-domesticated ones. Estimates of the size of the buffalo herds which once roamed the North American grasslands are in the range of only 50 to 100 million animals, so although one can’t be sure of the exact numbers of ‘big hairy things’, as Mr Coaker describes them, which were around before the advent of Homo sapiens and animal domestication, it seems very unlikely it was in the billions. In addition, one cannot simply compare and conflate the impacts of free-living species with those of domesticated breeds.

The present-day huge number of domesticated ruminants are not part of a natural cycle and they emit a significant amount of methane which, in turn, is an important and powerful greenhouse gas that is contributing to global warming. My advice to Mr Coaker is to keep googling but from now on to try some credible scientific sources on the internet.

Professor Bruce Webb Exeter, Devon