We've all heard of celebrities being vegetarians for ethical and/or health reasons, but the latest star push for the veggie lifestyle centers around climate change.

Yoko Ono and Paul McCartney (along with his daughters Mary and Stella) have come together in support of Meat Free Monday, a U.K.-based organization encouraging people to reduce meat consumption in order to cut carbon emissions.

According to Meat Free Monday, "The UK's Food Climate Research Network suggests that farm to fork is responsible for between 20-30 percent of global green house gas emissions. Livestock production is responsible for around half of these emissions."

To kick off the initiative, Ono and the McCartneys walked the event-appropriate green carpet at Inn The Park in London today (June 15).

For meat-lovers, giving up a juicy burger or pepperoni pizza once a week might not be the easiest thing, so the MFM website offers recipes and other helpful tips to help people get involved.

And while the program hasn't landed stateside yet, U.S. celebrities such as Kate Bosworth have already signed on.

Would you give up meat once a week for the environment? Or are you already a vegetarian? Leave a comment below.