what is the effect of cow's bacteria on global warming?

Answer 1

Cows intestinal bacteria release methane (a "green house gas"). Cows release this methane when they fart. Cows eat a lot so they fart a lot.

Its effect on global warming depends on how you see it. If you consider global warming as the unnatural current rise in temperature it has to come from unnatural sources. Cows would be farting no matter what and it would normally be dealt with naturally.

Cows farting isn't causing global warming, but it isn't helping.

However, humans are raising an unnatural number of cows so the effect of cow's bacteria on global warming can be listed as a human-related cause.

According to the EPA:
"Globally, ruminant livestock produce about 80 million metric tons of methane annually, accounting for about 28% of global methane" more specifically "[cows in the USA account for] 19% of global human-related methane emissions"

Answer 2

The EPA says: cattle in the US produce about 19% of the global methane caused by human-related sources.

Answer 3

Cow's bacteria contain carbon dioxide, the same gas found in car exhaust which contributes to the ozone layer's deterioration