Curbing methane emissions is important for climate change mitigation. Second only to carbon dioxide, methane is an abundant greenhouse gas and emissions from ruminant livestock are the largest source of human caused methane emissions (Ripple et al. 2014 Nature Climate Change).
Predicted livestock numbers were calculated using world livestock production data from 1961-2019 obtained from FAOSTAT. See FAOSTAT Methods & Standards for details on how livestock production is assessed. We estimated livestock totals in 2020 and 2021 separately for each species using non-seasonal Holt-Winters exponential smoothing models. The counter assumes a linear increase in livestock numbers from 2020 to 2021. We considered the developing countries to be those in Europe along with the United States, Canada, Australia, New Zealand, Russia, and Japan (see U.N. country codes). As of 2020, there are approximately 0.40 ruminants per person in the developed world and 0.55 ruminants per person in the developing world.
Global methane emission rates are given in metric tons per year for enteric fermentation only and assume 6.5 kg/yr for sheep, 45 kg/yr for cattle, 5 kg/yr for goats, and 50 kg/yr for buffalo. We obtained these estimated emission rates (averaging male and female rates) from: Crutzen, P.J., I. Aselmann, and W. Seiler, Methane production by domestic animals, wild ruminants, other herbivorous fauna, and humans, Tellus, 38B, 271-284, 1986.
Livestock methane counter developed by Chris Wolf () and William Ripple ().