The phrase "carbon emissions" gets tossed around a lot these days. You've almost certainly heard them in the same breath as "global warming" or "climate change," and most everybody out there has at least a pretty basic idea about where they come from. But, at the end of the day, what the heck are carbon emissions, anyway? Let's look a little closer at this ubiquitous term for these ubiquitos emissions.

Basics of carbon emissions

If you take one thing away from reading this, make it this point: Carbon emissions come from burning fossil fuels, which contributes to global warming. Every time you turn the ignition on your car, board an airplane, or (in many cases) turn on a light switch, you're creating carbon emissions.

Technically, though, carbon emissions should be called carbon dioxide emissions; we've gotten lazy and used to talking about them, and have shortened it. This is a small but significant difference, since carbon dioxide is one of the results -- probably the best known -- from all this fossil fuel combustion. So, carbon emissions = carbon dioxide emissions = contribution to global warming.

Even if your house doesn't have a chimney, it's still responsible for carbon emissions. Photo credit: Getty Images / Steve Allen

Carbon emissions: Who cares?

"Okay," you're saying, "so carbon emissions are created all the time, all around the world. So what?" Carbon dioxide creates the largest man-made contribution to the greenhouse effect, which is what is slowly, yet persistently, warming our globe. That makes it the most important greenhouse gas out there; it's currently responsible for about 10 - 25 percent of the greenhouse effect. Methane and ozone, the next two on the list, incidentally, don't crack the double digits, so carbon emissions are in the lead, in a bad way, when it comes to greenhouse gas emissions.

All this is to say, really, that we live not only in a carbon-based world, but a carbon emission-based society and economy, and the scope of activities that produce carbon emissions is just huge. Anything involving petroleum, coal, natural gas has a carbon emission ticket attached; that includes all cars and most transportation, the vast majority of our nations' electricity production (about half comes from coal alone), and a whole lot of home heating systems and even barbeques, just as a small snapshot.

Carbon emissions: The science (quickly)

Here's a quick tour of the science of carbon emissions. Fossil fuels, named so because they have ultimately been created of fossil-aged feedstocks (think dinosaurs) have been through millions of years of Earth's cycles, and now find themselves buried in the ground, under oceans, and other places not often directly in our backyards. They've had a long time to "stew," for lack of a better word, and have a high concentration of energy, which is why someone a few hundred years ago had the idea to use them for fuel.

So, these super-old, carbon-based, former dinosaurs are dug up and, in one way or another, lit on fire. They have high concentrations of carbon, which, when mixed with oxygen during combustion, create carbon dioxide (or CO₂). So, what was formerly interred in the Earth's crust is now out, and the carbon that was sequestered with it comes, too.

Cow burps and farts (yep, seriously) are a growing problem when it comes to greenhouse gas emissions. Photo credit: Getty Images / VisionsofAmerica / Joe Sohm

Carbon emissions: Beyond fossil fuels

So carbon emissions are created when we burn fossil fuels, but that's not the whole story. Activities that are often less prescient to many of us on a day-to-day basis have huge emissions, too. Land use changes -- mainly deforestation in the Amazon and other tropic areas -- account for almost 10 percent of global greenhouse gases. It's sort of a matter of addition by subtraction; more carbon emissions stay in the atmosphere as deforestation occurs, since trees and other plant life absorb carbon dioxide as they grow.

Livestock are also becoming a larger player in greenhouse gas discussions; though they tend to contribute more methane than anything, they still merit mention here. How do cows play in to this, you ask? Two words: Enteric fermentation. This is the process that takes place in the digestive systems of ruminants (like cows); without getting too deep into the microbiology behind it (trust me, it's kinda gross -- you can learn more from Wilipedia), basically, it results in an excess of methane being expelled from the animal. That's right: Cow burps and farts, as well as the decomposition of their poo, are serious contributors to greenhouse gases. Agricultural byproducts actually account for more than 10 percent of all greenhouse gas emissions -- and that's more than results from residential sources.

Reducing carbon emissions

I'd be remiss if I didn't mention how to reduce your carbon emissions, after all this about what they are, but let's keep this short and sweet. If you're an average American, your carbon footprint -- the measurement used to estimate your personal carbon emissions -- is about 20 tons. If you want to cut that number in half, follow these three steps and you'll have lost 10 tons in what seems like no time flat. Ahhh...

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