1. Become a vegetarian, or better yet a vegan. The share of greenhouse gas emissions from animal agriculture is usually pegged at 14.5 percent to 18 percent, but the Worldwatch Institute found lots of oversights in those calculations that, when properly counted, bring the ag contribution all the way up to 51 percent. That, you’ll notice, is more than half. Which means that after we clean up all the transportation, energy, industry and commerce in the world, we’ve done less than half the job. The other half is meat and dairy. Refuse to eat it. If this seems too challenging, consider giving it up one day a week. It will still be the most important action you can take.