Chapter 3.3: Carbon Cycling, Where It Stays And Where It’s Going  

CARBON IS ALWAYS ON THE MOVE. IT CIRCULATES AROUND THE PLANET, TAKING ON DIFFERENT FORMS AND PLAYING DIFFERENT ROLES IN OUR EARTH SYSTEMS, OFTEN IN WAYS THAT ARE NOT APPARENT TO US. When you teach about the carbon cycles, it’s good to help students understand how it works rather than just describing its details and vocabulary.

The bathtub

Students have a hard time thinking about the stocks (also known as sinks, where carbon is stored) and flows (how it moves and how much of it moves) between those stocks.

To help them understand a metaphorical representation of this. I refer to the IPCC’s “Worlds Apart” bathtub drawing. I usually cover up part of this representation (using PowerPoint) and just show learners one segment at a time. I start with the carbon dioxide in the bathtub and explain what that is. The rest of the drawing, other than the bathtub, is covered up. Then I reveal the natural carbon cycle in lower left along with the pipe that is filling up the tub on that side. The students and I have more conversations. Next up is the natural land and ocean carbon sinks (far bottom left). We talk about a “balanced flow” of in and out, and it makes sense to them—but they know what is coming next.

Then I show the “Human Disturbance” cycle image and the tap that is in the upper right. We discuss what creates the carbon dioxide in that tap. Question to students: If these are the inputs and outputs to our atmosphere, what do you think is going to happen and under what conditions? Finally, I reveal the engineered and natural “negative emissions” in the bottom right corner. Regrettably, I have to tell them that “engineered” means that we have to remove carbon artificially, by direct carbon capture from the air, for which technology exists, the only problem is that it’s just about one-millionth the scale of what would actually make a difference.

I’m linking here a PowerPoint slide that does this gradual reveal; you can adapt as necessary.

Other resources about the carbon cycle in combination with solutions

This is a game called Stabilization Wedges. It is a simple framework for understanding both the carbon emissions cuts needed to avoid dramatic climate change and the tools already available to do so.

NSTA Press has a book called Crosscutting Concepts: Strengthening Science and Engineering Learning, by NSTA Press. There’s a chapter called Energy and Matter: Flows, Cycles, and Conservation byCharles W. (Andy) Anderson, Jeffrey Nordine, and MaryMargaret Welch. I can’t link a download here, but here’s where to find it. it is a great read to help you understand how carbon moves and has ideas for teaching these concepts.

Informative video, some of which may be viewable by students. It is called eCLips Carbon Cycle.

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