Next time you feel like ordering a double-bacon cheeseburger, consider this: 51 percent of all climate change emissions comes from the production of meat, according to a controversial new study by the WorldWatch Institute, a well-respected U.S. think tank.

This figure is much higher than previous studies have suggested, such as the United Nations’ 2006 report, Livestock’s Long Shadow.

That’s because previous studies have severely underestimated the greenhouse gases caused by tens of billions of cattle, sheep, pigs, poultry and other animals in three main areas: methane, land use and respiration, said the study's authors in a recent article by The Independent.

This results in an amount far greater than the U.N. estimate of 18 percent. 

According to the recent study’s authors — Robert Goodland, a former lead environmental adviser to the World Bank, and Jeff Anhang, a current adviser — domesticated animals cause 32 billion tons of carbon dioxide equivalent (CO2e), more than the combined impact of industry and energy.

In addition, they argue that scientists have significantly underestimated livestock's methane emissions — i.e., farts and belches.

Backing up that estimate is a recent study by NASA scientists that found methane has 33 times more effect on climate change than carbon dioxide, compared with a previous factor of 25.

The authors also say that official figures shouldn't ignore CO2 emitted by breathing animals based on the assumption that emissions are entirely offset by photosynthesis of the animals’ food.

Concerning land use, the authors calculated that returning the land currently used for livestock to natural vegetation and forests would remove 2.6 billion tons of CO2 emissions from the atmosphere. They also believe that the U.N. underestimated the amount of livestock by putting it at 21.7 billion against other estimates of 50 billion.

Though many won’t endorse the new findings until they’ve been properly reviewed, advocacy organizations like Friends of the Earth said the report strengthens the argument that the government needs to take meat's carbon footprint seriously. 

“We already know that the meat and dairy industry causes more climate-changing emissions than all the world's transport," said Clare Oxborrow, senior food campaigner. "These new figures need further scrutiny but, if they stack up, they provide yet more evidence of the urgent need to fix the food chain. The more damaging elements of the meat and dairy industry are effectively government-sponsored: millions of pounds of taxpayers' money is spent propping up factory farms and subsidizing the import of animal feed that's been grown at the expense of forests."

Whether the new report holds up to peer-review remains to be seen, but the report raises a consideration for consumers: Giving up meat could be one of the most important things that a consumer can do to help reduce his environmental footprint.

“If this argument is right," wrote Goodland and Anhang, "it implies that replacing livestock products with better alternatives would be the best strategy for reversing climate change. ... In fact, this approach would have far more rapid effects on greenhouse gas emissions and their atmospheric concentrations than actions to replace fossil fuels with renewable energy.”

For tips on how to reduce your own daily meat intake, check out the Farm Sanctuary's Veg for Life campaign.

Also on MNN: 

• MNN blogger warns the tofu set not to gloat. 

Meet your meat
Controversial study says meat production creates half of all climate change emissions.