Methane (CH4) is significantly more effective than CO2 at trapping heat in the atmosphere: by a factor of 28 over a 100-year time frame based on the IPCC Fifth Assessment Report estimate (IPCC 2013). Over the last 250 years, the concentration of CH4 in the atmosphere increased by 161.9 percent (IPCC 2013; NOAA/ESRL 2024b). Within the United States, the main anthropogenic sources of CH4 include enteric fermentation from domestic livestock, natural gas systems, landfills, domestic livestock manure management, flooded land, coal mining, and petroleum systems (see Figure ES-8).
Significant trends for the largest sources of anthropogenic CH4 emissions include the following:
- Enteric fermentation was the largest anthropogenic source of CH4 emissions in the United States in 2022, accounting for 27.4 percent of total CH4 emissions and 3.0 percent of total gross emissions. Emissions have increased by 5.2 percent (9.5 MMT CO2 Eq.) since 1990. This increase in emissions from 1990 to 2022 generally follows the increasing trends in cattle populations.
- Natural gas systems were the second largest anthropogenic source category of CH4 emissions in the United States in 2022, accounting for 24.6 percent of total CH4 emissions and 2.7 percent of total gross emissions. Emissions have decreased by 20.9 percent (45.7 MMT CO2 Eq.) since 1990, largely due to decreases in emissions from distribution, transmission, and storage.
https://www.epa.gov/system/files/documents/2024-04/us-ghg-inventory-2024-main-text_04-18-2024.pdf
Methane from cows and other livestock is absolutely a big problem, it's more than all the known gas leaks from fossil fuels in the United States. There are probably a lot more gas leaks we don't know about, but that doesn't diminish just how much methane we know livestock produces.