4.0% of green house gas emissions come from the global dairy industry
Cows, Sheep and Goats are ruminants which means when they breakdown cellulose in their rumen they produce methane. This methane is 'burped' out by the animal and into the atmosphere.
Other factors like manure to grow animal feed also contribute to climate change.
Although methane doesn't last as long in the atmosphere as Carbon Dioxide, it has a more pronounced effect on climate change and still takes 20 years to breakdown.