When we talk about the role of fossil fuels in climate chance, what we're really talking about is the carbon cycle. That's the term that scientists use to describe the different forms that carbon is stored in on the earth, and the different ways that it can move from form to form. Understanding the carbon cycle is one of the keys to understanding both the effect of burning carbon-based fuels and the issues involved in trying to take carbon dioxide out of the atmosphere. According to a paper in the latest edition of Science, there may still be some pretty significant gaps in our knowledge of the carbon cycle. In particular, it looks like our understanding of the way carbon moves through the oceans may have been suffering because we didn't know poop about fish poop.

Before we get down to the gritty details and talk about what poop has to do with anything, it might be good to start with a quick review of the carbon cycle. Actually, it might be even better to start with a quick review of one of those concepts that we all learn in third-grade physics, but don't think about much in our day to day world: the law of conservation of mass/matter.

Matter is not created or destroyed. Therefore the amount of mass in a closed system will remain constant no matter what happens.

Like most things in science, that might be a bit of a simplification, but when we're looking at something the size of the Earth, it's good enough. Relativity, quantum mechanics, and space dust might all complicate things a bit, but not enough to matter. For our purposes, we can reasonably assume that all the carbon that we're putting into the atmosphere in the form of carbon dioxide has been here since the earth was formed, and that if we want to take the carbon dioxide back out of the atmosphere, we're going to have to find somewhere on this planet to store the carbon.

With that in mind, let's look at the some of the more important ways that carbon can move through the crust, oceans, and biosphere, and atmosphere.

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