It's no secret that cow burps and farts are a significant source of greenhouse gas emissions. As Slate reported last November, "the typical cow belches forth about a third of a pound of methane per day." It adds up.
But how do we know such things? It's one thing to assert that cow burps contribute to global warming, it's another to do the hard, painstaking scientific work of measuring bovine belching. Do you want to strap a big red balloon to the back of a cow so you can capture its farts? I sure don't.
But I respect those who do. Which is why I mildly recommend watching the following 24 second video clip from the BBC, "Cow Burps Help Climate Study," which purports to show how "Argentine scientists are studying the effects of global warming by strapping plastic tanks to the backs of cows to collect their gas."
How the World Works agrees with Globalisation and the Environment: the video is "oddly pointless but compelling."