How bad is cow methane for the climate?

The objection

“Methane breaks down in a decade, it’s a distraction. CO2 from fossil fuels is the real problem.”

The answer

Part of this is right. Warming comes mainly from burning fossil fuels, and the CO2 that causes most of it lingers in the air for centuries [4], while methane lasts about 12 years on average (IPCC, 2021) [1]. Measured by the extra heat each gas traps because of its rise since 1750, CO2 accounts for 2.16 watts per square metre and methane for 0.54, about a quarter as much (IPCC, 2021) [1]. Counted by emissions instead, which adds the ozone and stratospheric water vapour that methane produces in the air, the IPCC (2021) puts methane’s figure at 1.19, more than double the 0.54 and over half of CO2’s [2]. Either way methane comes second only to CO2 among the greenhouse gases, and farming is the largest human source of it [3].

How much more heat does a tonne of methane trap than CO2?

Over 100 years a tonne of methane from cattle traps about 27 times as much heat as a tonne of CO2, and over 20 years about 80 times, on the IPCC’s figures (2021) [1]. Methane from fossil fuels scores slightly higher still, 29.8 and 82.5, because the IPCC also counts the fossil CO2 it leaves behind when it breaks down [1].

How much human-caused methane comes from livestock?

Livestock produce about 32% of human-caused methane, according to the UN’s Food and Agriculture Organization (FAO, 2025), and with rice paddies’ 8% that puts agriculture at about 40%, ahead of fossil fuels and waste [3]. Most livestock methane is burped out as microbes in the rumen ferment grass and feed, with manure adding more, and cattle alone produce around 75% of the world’s enteric methane, the burped kind [3]. The IPCC (2021) found that the sectors causing the most warming in the near term are the methane-heavy ones: fossil fuel extraction and distribution, agriculture, and waste [2].

Does the usual figure overstate the warming from cattle?

The IPCC (2021) found that converting methane to CO2 with the 100-year figure overstates the warming from constant emissions, such as those of a herd that stays the same size, by a factor of 3 to 4 [1]. It errs the other way for a new source, understating its warming by a factor of 4 to 5 over its first 20 years [1], so it flatters a growing herd while penalising a stable one. GWP*, a newer metric, is designed to capture both effects [1], and the steady herd is also at the heart of the claim that cow methane is just part of a natural cycle. Myles Allen, one of the Oxford scientists who created GWP*, told Carbon Brief (2025) that the livestock sector is “unsustainable globally”, with animal numbers and methane levels still rising [4].

Would cutting cattle methane slow warming quickly?

Sustained methane cuts, wherever they happen, stand out for slowing warming in both the near term and the long term, the IPCC (2021) says [2]. Under GWP*, methane emissions stop adding new warming once they fall by about 10% over 30 years, around 3% a decade (Carbon Brief, 2025) [4]. Allen’s view is that livestock farming does not have to disappear to stop global warming but does need to start shrinking, and that cutting its methane faster than 3% a decade would help undo some of the warming the sector has already caused [4].