> The carbon footprint of cows is still horrendous.

A constant number of cows produce a constant amount of methane which plateaus quickly due to its very small atmospheric half-life.

"Additional methane emission categories such as rice cultivation (RIC), ruminant animal (ANI), North American shale gas extraction (SHA), and tropical wetlands (TRO) have been investigated as potential causes of the resuming methane growth starting from 2007. In agreement with recent studies, we find that a methane increase of 15.4 Tg yr−1 in 2007 and subsequent years, of which __50 % are from RIC (7.68 Tg yr−1), 46 % from SHA (7.15 Tg yr−1), and 4 % from TRO (0.58 Tg yr−1)__, can optimally explain the trend up to 2013." - ["Model simulations of atmospheric methane (1997–2016) and their evaluation using NOAA and AGAGE surface and IAGOS-CARIBIC aircraft observations" (2020)](https://acp.copernicus.org/articles/20/5787/2020/)

"On November 17, 2003 National Oceanic and Atmospheric Administration reported that the concentration of the potent greenhouse gas methane in the atmosphere was leveling off and it appears to have remained at this 1999 level (Figure 1). The Intergovernmental Panel on Climate Change in 2007 acknowledged that methane concentrations have plateaued, with emissions being equivalent to removals. These changes in methane atmospheric dynamics have raised questions about the relative importance of ruminant livestock in global methane accounting and the value of pursuing means of further suppressing methane production from ruminants. At this time there is no relationship between increasing ruminant numbers and changes in atmospheric methane concentrations changes, a break from previously assumed role of ruminants in greenhouse gases (Figure 1)." - ["Belching Ruminants, a minor player in atmospheric methane" (2008)](http://www-naweb.iaea.org/nafa/news/2008-atmospheric-methane...)

«If there was an increase in atmospheric CH4 mixing ratio and the increase was caused by agricultural sources, specifically livestock emissions, the trends in atmospheric CH4 should correspond to dynamics in global livestock populations. *During 1999 to 2006, however, when atmospheric CH4 mixing ratio plateaued, global cattle and buffalo populations* (these species make up 84% of all livestock enteric CH4 emissions; FAOSTAT, 2017) *continued to increase* from 1.46 (1999) to 1.59 (2006) billion head (FAOSTAT, 2017), at a rate of approximately 18.8 million head/yr, *which apparently did not affect atmospheric CH4* over the same period. Since 2006, the rate of increase for the populations of these ruminant species declined to 7.3 million head/yr (FAOSTAT, 2017); we note that FAOSTAT does not specify uncertainty for their estimates, which is likely large for cattle inventories (and emission factors) in developing countries. Thus, it appears that *the global dynamics in large ruminant inventories do not support the suggested farmed livestock origin of the increase in atmospheric CH4* from 2006 to 2015. Potential increases in CH4 emission from non-livestock agricultural sources to the global CH4 budget cannot be excluded. Globally, *the area harvested for paddy rice* (emissions from which are typically 22 to 24% of the emissions from livestock), for example, *had increased 42% from the 1960s to 2015* (FAOSTAT, 2017), although new rice varieties (i.e., water-saving and drought-resistance rice, or WDR; Luo, 2010) require less water and thus emit less CH4 (Sun et al., 2016).»

«As pointed out by Turner et al. (2017), fossil fuel CH4 is not entirely thermogenic in origin (based on its isotopic signature), with *over 20% of the world's natural gas reserves generated by microbial activities (i.e., carrying biogenic isotopic signature)*. Thus, collectively, we can conclude that quantitative attribution of changes in atmospheric CH4 concentrations to CH4 sources based on δ13CH4 data is at least questionable.» - ["Symposium review: Uncertainties in enteric methane inventories, measurement techniques, and prediction models" (2018)](https://www.sciencedirect.com/science/article/pii/S002203021...)

"we find that city-level emissions are 1.4 to 2.6 times larger than reported in commonly used emission inventories and that the landfills contribute 6 to 50% of those emissions" - ["Using satellites to uncover large methane emissions from landfills" (2022)](https://www.science.org/doi/10.1126/sciadv.abn9683)