When you eat a hamburger, you aren’t just causing a cow to suffer; you are also supporting an industry that is rapidly destroying our water, air, soil, and forests. It takes an estimated 4.8 pounds of grain, 390 gallons of water, and .25 gallons of gasoline to produce a pound of beef. Livestock production requires 10 to 1000 times more land, energy, and water than is necessary to produce an equivalent amount of plant food. The Earth could support a vegetarian population many times its present size. But the current world population could not be sustained on meat-based diets. Non Government Organizations (NGOs) such as Green Your Plate social media campaign, raises awareness surrounding livestock contributions to climate change.
Ironically the way that factory farming is done today poses tremendous risks to climate change. This stems from a reliance on corn for feed, pooling manure into stagnant lagoons that release methane, use of petroleum-fueled machinery, and pollution to air and water which have unknown consequences for global warming. Two issues exacerbate the global warming issue. These are the corn and manure problems.

The Corn Problem

The US corn industry is the most heavily subsidized farm crop of all, and so we have a huge excess of corn. A good chunk of that corn does not taste good, has low nutrient value, and is meant to be used as livestock feed. However, cows have special stomachs meant to eat grass, not corn. This is explained in detail in this New York Times piece (Pollan, 2002):

A corn diet can also give a cow acidosis. Unlike that in our own highly acidic stomachs, the normal pH of a rumen is neutral. Corn makes it unnaturally acidic, however, causing a kind of bovine heartburn, which in some cases can kill the animal but usually just makes it sick. Acidotic animals go off their feed, pant and salivate excessively, paw at their bellies