"I have to admit that when it comes to food, I’m a total sucker. Whether it’s sugar or grease or carbs, pretty much bring it on! And I spend a lot of time in Montana, so for me, that medium rare, grass fed ribeye steak? Pretty much as good as it gets. I know. I don’t do it often and when I do, I gotta admit I feel a little conflicted. And that’s for a lot of reasons, including the planet. But how big of a problem is what I eat? I mean, does it really make much of a dent in something as huge as global warming? It turns out, what we put on our plates matters a lot. About 25 percent of all the global climate change problems we’re seeing can be attributed back to the food and the choices that we’re actually making about what we eat on a daily basis. This is greater than all of the cars on the planet. In fact, it’s about twice as much global warming pollution as the cars. Ben Houlton and Maya Almaraz study the connection between climate and diet at the University of California, Davis. They track how the way we produce food creates greenhouse gases that contribute to global warming. With their data, the team has crunched the numbers to figure out how much carbon pollution is produced by different foods and different diets. A lot of people feel really helpless when it comes to climate change, like they can’t make a difference. And what our research is showing is that your personal decisions really can have a big impact. So, take that grass fed ribeye steak I love. If you really look at everything that went into making a single serving of beef, you end up emitting about 330 grams of carbon. That’s like driving a car three miles. Now, if I choose to have chicken instead, there’s more than a five-fold drop in emissions. Switch to fish and you see the number go down even more. Now, look at veggies. If I swapped beef out entirely for lentils, well, I’m down to practically nothing! So, why does beef and lamb, too, for that matter - pack such a powerful punch to the planet? Livestock accounts for a little over 14 percent of global greenhouse gas emissions. If that sort of seems low to you, consider it’s about equal to transportation. We’re talking all the cars, trucks, planes, trains and ships on the planet combined! This is partly because ruminant animals like cows and sheep - they’re just gassy! And the methane they produce is at least 25 times more potent than carbon dioxide. Plus it takes lot of land, fertilizer and about a billion tons of grain to feed all that livestock. And you could feed 3.5 billion people with that grain; if we were just directly eating these grains ourselves, it would eliminate a lot of the CO2 that is emitted from cattle production. So it’s clear that meat has a pretty big carbon load, but it’s also worth remembering that not all livestock is raised equally. In parts of the American West, for instance, ranchers are working to raise livestock in ways that actually help restore the land. And they’re experimenting with ways that soil and grasslands can be used to keep carbon pollution out of the air. But even these sustainable ranchers will really tell you, we’re probably eating too much meat. I know a lot of people who if you don’t serve them meat for lunch or dinner, they’re kind of like ""well, when is the meat coming out?"" It's to the point now where the U.S. actually has one of the highest meat footprints per capita. So, what about not eating meat at all? Vegan is the way to go for the least impact on the planet, but it’s not that much different, in terms of emissions, than say, a vegetarian diet. And the team found that the environmental impact of the Mediterranean diet is pretty similar to vegan and vegetarian diets. It’s a lot less meat-heavy than what Americans are used to - so, fish and poultry a few times a week; beef maybe once a month, plenty of plant-based foods, and of course, loads of olive oil. Eliminating like 90 percent of your meat intake is more important than eliminating all of your meat. We don’t all have to be vegan. We don’t all even have to be vegetarian. If we can just reduce our meat intake, every little bit helps. And if you can bring it down a lot, you can help the climate a lot. If we all just switched to a Mediterranean diet, it could actually solve 15 percent of global warming pollution by 2050. If everyone were to move towards it, that is equivalent to taking somewhere around a billion cars off of the streets, in terms of vehicle emissions each year. So, that kind of a footprint is big-time. But say you still want more meat than the Mediterranean diet recommends? Just cutting down your portion size to the doctor-recommended 4 ounces can reduce your emissions by half. That’s huge! In fact, the doctors are telling us we’re eating about twice as much meat as we really need for a healthy diet. The good news is, we are listening to our doctors. In the last decade, there’s been a 19 percent drop in the amount of beef we eat. All these things that you're already being told are good for you also happen to be good for the planet. So what we eat really is a big part of the climate puzzle. I mean, we may not all be able to afford an electric car or putting solar panels on our house, but we all have to eat every day. And these choices we make can add up to really big numbers. And since meat has a pretty big carbon load, we need to be thoughtful about how much we eat. As for that ribeye steak that I really love, I am honestly trying to cut back! Maybe it’s just a smaller piece of steak; or simply swapping out a meat dish for a veggie burger. It may seem like a small thing, but it really does add up to big impacts. Hey, so what did you have for dinner last night? Find out how your choices are affecting global warming by taking a quiz at climate.universityofcalifornia.edu or watch one of our other episodes to discover what happened when I brought a box of donuts to MIT."