A hyper-conscious environmental sort from Missoula recently wrote in to the Sierra Club to settle a debate he was having about the impact of pets on the environment. He apparently has a killjoy of a friend who tried to tell him that owning a dog has a worse environmental impact over the dog's lifetime than owning a Hummer. Come on, now, friend.

As Sierra Club blogger Schildgen clarifies, while a dog on an all-beef diet is going to have some impact, it pales in comparison as a carbon footprint to own a 15-mile-per-gallon Hummer.

To compare dogs and Hummers, I figured that driving the typical 12,000 miles a year in a Hummer would burn around 800 gallons. At 125,000 British thermal units per gallon, that’s 100 million Btus a year. Then, I assumed a stupendously extravagant dog diet of a pound of beef--the most energy-intensive meat--per day. Because dogs need to eat the equivalent of 2 percent of their weight every day, this seems a fair amount, though it fails to give credit the teeny-weeny actual and ecological footprints of Chihuahuas, toy poodles, and other micro-canines. But erring on the side of wolfhounds, a population of some 74 million dogs would consume around 28 billion pounds of beef--roughly all the beef now eaten in the United States.

How much energy would this luxury doggy diet require? According to the latest energy numbers from the USDA, the total energy expended on beef production, shipping, refrigeration, etc. is around 395.5 billion Btus. So even on an all-beef diet, the individual dog’s share would be 5.25 million Btus, or only a bit more than 5 percent of the energy burned by a Hummer in a year.

So, in summation, dog ownership, assuming you have not forced the dog into some crazy vegan diet (which apparently is sort of healthy?) will have a greater impact on the planet than, say, riding a bicycle. But probably not as great as driving a Prius.

And if you listen to the fictional EPA guy on this week's episode of The Newsroom, you'll know that we're all doomed anyway so why bother worrying.