Carbon Matters

Middle school students get carbon cycle literate

By Jana Dean

Illustrator: Erik Ruin

It was the day after Hurricane Sandy, and Eli and Krishna rushed into class with a question: “Ms. Dean, can it happen to us?” They’d seen images of buildings flooded up to the second story and cars that had floated to rest on top of each other. Our West Coast bayside town has early 20th-century buildings that look something like those flooded by Sandy in early 2013, and the students already knew that our streets flood when high tide, low air pressure, and heavy rainfall combine. The water backing up into storm drains in our streets has increased because of rising seas due to heat trapped by our carbon-laden atmosphere. Eli and Krishna gave me an exciting opening to connect their up-to-the-moment concern to the biology, geology, and physics of climate change. I knew I could squeeze a lot of relevant science out of just one hurricane.

I was in for a surprise, however. The first time I mentioned climate change, Trevor’s dad sent me an email insisting I “balance the science” and teach students that global warming may not be happening at all. Ultimately, this parent’s persistent scrutiny, as uncomfortable as it made me, had a silver lining. Instead of treating humanity’s effect on the atmospheric system generally and broadly, I decided to isolate the carbon cycle from climate change and help students explore the difference between the short and long carbon cycles. As a result, they became more informed about the science behind climate change than most of the adults in their lives.

Carbon cycles and, as it does, it changes form by bonding with other elements. It bonds with hydrogen to make the carbohydrates in plants and animals. It bonds with calcium to make the shells of sea creatures. It bonds with oxygen to make atmospheric carbon dioxide.

In the short term, carbon shifts from CO2 in the air—through both photosynthesis and digestion—to the starches and sugars that make up all living tissue. Then it shifts back to CO2 and methane through respiration and decomposition. Over millennia, carbon-holding plants and animals are compressed by layers of sediment into coal and oil, becoming hydrocarbons. When burned as fuel, coal and oil break down into CO2, which is suddenly released back into the atmosphere. What matters in climate science is not whether carbon enters the atmosphere, but how fast the carbon cycles from the atmosphere to living organisms, to rocks and oil, and back again.

Both the short and long carbon cycles happen all the time. For example, eat a sandwich and you are participating in the short cycle: The plants and animals you are eating stored that energy in the last year at most. In contrast, drive your car to the sandwich shop and you are appropriating stored energy from deep time for a 10-minute excursion. Recognizing the difference between these two carbon cycles is a must for comprehending the link between burning fossil fuels and climate catastrophes like Hurricane Sandy.

The day after Krishna and Eli’s questions about sea levels rising, I built interest for the rest of the class by showing students a cartoon from the “Week in Review” section of the New York Times. It depicts the Statue of Liberty with visitors arriving in dive suits. I asked students what they thought the cartoon was all about. Hands shot up. “Hurricane Sandy in New York City.” “It’s like New Orleans.” “Hurricane Katrina.” Although students had plenty of knowledge about big storms, no one mentioned the underlying phenomena making such events more common and more catastrophic. They weren’t yet connecting atmospheric carbon to the global rise in temperatures, storm frequency, and sea level. This seemed a perfect place to begin. If I proceeded step by step, I’d be able to build from what students knew to bring them to an understanding of one of the most important issues facing their generation. Usually I start a unit with a survey to find out what students know about a topic. This time, I relied only on that opening discussion and didn’t anticipate Trevor’s parent’s coming challenge. I went ahead and told them that what had happened that week on the East Coast was due to climate change.

We used a page on the New York Times website to connect rising sea levels to carbon emissions (see Resources). The page uses models based on current carbon emissions and projected reductions in carbon emissions to foretell future shorelines in U.S. cities. I asked my 6th graders to look for anything that surprised them. Miami turned out to be the star attraction: The entire city is expected to be underwater in a century or two. I wanted the class to move past the sensational, however, and think critically about what they were seeing. I asked them to think about why some cities would be affected so much more than others. For example, why do the models predict that Seattle will lose only 13 percent of its land to the sea while places like Boston and Tampa Bay—37 and 50 percent, respectively—lose so much more?

Most students were able to infer that the differences are due to topography. If your city is flat, you flood. If you have hills, high ground will save you. This realization resulted in a heated discussion about the value of location. The neighborhood around our school sits on a ridge between two inlets. Sam said, “I’m going to be fine.” He gestured to the northeast. “My house is right over there. I can walk to the water, but it’s all downhill. I get tired coming home.” Kathleen looked stricken. She and her mom live in a cottage by the bay. Inwardly, I cringed. My aim with such young students is to build urgency, not to scare them so much they quit being curious. I asked, “Do you have stairs to the beach?” She nodded gravely. I answered, “Then you probably are on high bank. Although we don’t really know for sure, that will likely give you more time.” She relaxed, her immediate concern allayed. Then I drew cross sections showing the difference between high bank and low bank on the board. Most students quickly saw that those desirable low-bank beach properties came with a distinct future disadvantage. Isaiah didn’t agree. “If you don’t like where you’re living, you can just move.” I didn’t want to leave the class there, thinking there wasn’t anything to worry about because it’s not happening tomorrow—or that the only consequence of climate change would be the arrival of the moving van.

When I teach about environmental issues I want students to realize that not everyone experiences the same impact. I asked students to talk to a partner about whether they thought sea level rise was fair. This launched a vigorous debate. Ava echoed Isaiah’s earlier comment, saying people can move from endangered areas. But Lila stomped her foot and insisted, “There are places in New Orleans that are really beautiful. People live there and they love it. Their grandparents lived there and they live there now, and they don’t want to move.”

I temporarily cut off the debate to air a short video posted on YouTube by the United Nations: Tuvalu: Sea Level Rise in the Pacific, Loss of Land and Culture. Students learned of the impending demise of the entire nations of Tuvalu and Kiribati, despite the fact that these remote islands have few carbon-emitting cars, factories, or power plants. These long-habitable atolls just happen to be low. I then directed students to take a stand on a continuum. If they thought sea level rise was fair, they would stand at one end. If they thought it wasn’t fair, they’d stand at another. They could also stand anywhere else on the line if they saw that it was some balance of fair and unfair.

Students spread up and down the line and continued to voice their perspectives. Sam remained confident about his safety at the “fair” end: “I know the bay’s close by but I live up here on this hill. I’m going to be fine.” At the other end of the line, Keisha passionately spoke for the Tuvaluans: “What are they going to do? Drive away? They live on an island!” Sam crossed his arms and exclaimed, “I don’t know why we’re even talking about this.” Sam’s resistance was nothing compared to what was quietly simmering in Trevor. Little did I know I’d thrown Trevor into a moral crisis. He remembered that I had mentioned climate change as the cause of all these shifting shorelines. As class ended, he said, “But Ms. Dean, what if I don’t believe in global warming?”

I asked, “Are you willing to learn more about it?”

He responded reluctantly, “Yes?”

Even though Trevor’s skepticism about climate change shouldn’t have surprised me, it did. Our city council passed its first climate action plan way back in 1991, and in 2013 signed a resolution opposing the CO2 disaster of new coal export facilities. The school district has a carbon emissions reduction plan and incorporates energy efficiency features in new construction. Transit runs on biodiesel and trumpets the reduction in carbon emissions on the back of every bus. People here have been publicly and actively tracking climate change for decades.

That afternoon I got the first email questioning my motives and asking for a balanced approach. Trevor’s dad hoped his son was getting an understanding of “both sides” of the climate change issue. He went on to tell me that, even though he didn’t have a problem with the “theory” that climate change is a reality, he disagreed and wanted his side to be discussed. He asked that I present the argument that it isn’t happening after all. I took a deep breath and answered him, cc-ing my principal. I wrote about the sources I’d used thus far (the UN video and the New York Times) and that I’d next be using Climate Hot Map: Global Warming Effects Around the World, a website curated by the Union of Concerned Scientists. I reassured Trevor’s dad: “Everything on the site is backed by peer-reviewed research and presented in a form accessible to 6th graders.”

I chose the Climate Hot Map because a few students remained convinced that sea level rise was a problem easily solved by human migration. If I wanted to get them engaged in the science of climate change, I’d have to persuade them that it mattered. Climate Hot Map provides links to global warming-related studies from around the world. It would allow them to see and understand crises like wildfires and water shortages. I provided a brief introduction for each of the organizational categories on the map: people, freshwater, oceans, ecosystems, and temperature. I told them to choose what interested them most, to activate those links, and then to identify the three phenomena that most alarmed them. I added: “Everything on this map is a result of climate change. We’ll learn more about what causes climate change later.”

After using a class period to explore the site, students presented their greatest concerns. Forrest worried about wildfires in Australia due to increasingly low rainfall and high heat. Grant noted arctic amplification, which is an alarming feedback loop: Melting ice uncovers darker land or ocean beneath, which then absorbs more sunlight, causing more heating. Sara passionately described the plight of Bordeaux vintners, although she would need to wait a few years to sample their wares. Afterward, I had them meet in geographically similar groups to discuss their concerns in detail. After discussion, they wrote to the following prompt: In a paragraph, describe what concerns you most about climate change. Explain what makes you care so much.

Students’ passion surprised me. In my class, students draw an icon to represent the content on every page of notes or writing they create. For this assignment my 6th graders chose sad faces and stick figures with dark clouds over their heads. Isaiah ended his paragraph about aquacultural and agricultural issues in northern Europe with a wry “We need to take action on emissions (sorry, SUV fans).” Devi wrote about how rising water temperatures “contribute to all kinds of disasters like coral bleaching, krill killing, and fish killing.” He ended his paragraph by saying, “We can all stop global warming by using less emissions. Helping now is our only hope for survival.” Then Meera offered her concern for forests: “The mountain pine beetle eats trees and causes tree disease. Because of the increased temperatures from climate change, these tree-infecting beetles can survive through winter and multiply rapidly. This saddens me because when so many trees die (24.5 billion acres in British Columbia since 1994) the carbon levels in the atmosphere rise even more.”

By then, Trevor’s dad had begun transmitting an almost daily influx of links to sources refuting any need for concern about climate change. I was a good sport. I spent entire evenings investigating the links he forwarded. As I tried to understand the science that called climate change into question, I didn’t come up with anything I could share with my young scientists. Climate critics pointed to nonhuman sources of atmospheric CO2, like volcanoes, or the vast stretch of prehuman geologic time during which temperatures fluctuated wildly. Some sources touted a slight dip in global average temperature in 2009. I did learn a lot from one site called “CO2 Science” about the power of photosynthesis, but its authors didn’t consider the qualitative difference between the short carbon cycle (your sandwich) and the long one (the ancient hydrocarbons in your gas tank.) When I entertained the idea of bringing the “other side” to life so that students could decide for themselves whether climate change was happening, the string of lessons in graph reading and research analysis seemed endless, and I knew it would take me far away from my job of teaching science. Meanwhile, Trevor was increasingly silent and his dad’s emails kept coming.

I went to my principal for help. His advice: “Drop the words climate change and global warming and just teach the carbon cycle.” When I answered that all the resources I’d found exist only because of the need to teach about climate change, he insisted: “Teach the kids the difference between politics and science. Politics is when we interpret the science and take action. We want people to make decisions based on science, right? So teach them the science and then connect the science to politics.”

I wasn’t sure I completely agreed with his take on the problem. I was concerned that teaching about the issue without terms so widely used in the media would make it far less relevant and meaningful to my students, not to mention contradict current scientific consensus. But I didn’t know what else to do, so I gave it a try. At the beginning of the next class I laid out the next few weeks.

First, I acknowledged the deep feelings in their sad-face and anger-cloud stick figures. I explained that passion makes you want to take action and science helps you know what action to take. Then I let them know that my job was to teach them science. I cited specific state standards having to do with systems and environmental issues and assured them that as a class we’d come to climate action based on the science. My doubter sat in the front seat. I’ve never had a 6th grader take such elaborate notes. He copied down every single word I spoke and every phrase I placed on the power point, and even asked me to repeat myself so he could get it all down.

That same day, students compared a windup watch (a closed system) to the digestive system of a dog (an open system) and identified open and closed systems they encountered in their lives and in the classroom. I ended the class by explaining that the Earth is a closed system. Except for inconsequential additions of matter in the form of errant asteroids, what’s on Earth doesn’t come or go, even though it continually shifts and changes form. “The movement of matter on the Earth,” I told students, “is called a cycle. This applies to carbon, which is what will matter once we have enough information to take action on climate change.” It would be weeks before I uttered the term climate change again.

Next, students did a lab right out of our district-adopted FOSS (Full Option Science System) life science materials. They weighed water and celery stalks before and after letting the stalks stand in water for 24 hours. The water seems to disappear from the vials. And it disappears the fastest from vials where the celery has the most leaves. Control vials eliminate evaporation as the cause. Given the relatively unchanged weight of the celery, the students determine that the plant must “use” the water for something. In fact, in photosynthesis, plants capture the C in CO2 and the H in H2O. In this way, they convert sunlight energy to chemical energy and store it as carbohydrates. As I explained the process to students, I was careful not to mention climate change. With the omission of the trigger phrase, Trevor relaxed in his note taking and the messages from Dad abated. It seemed Trevor could now happily learn some science along with his friends.

Then students investigated the way a finite amount of carbon cycles through the Earth’s closed system. Using lessons from the California Academy of Sciences, they identified objects containing carbon, including plant materials, plastic, soda pop, and seashells. They acted out the movement of carbon from the atmosphere (air), biosphere (living organisms), hydrosphere (water), and lithosphere (rocks). After a role play, in which dozens of donated tennis balls became flying carbon atoms, they created posters to illustrate the carbon cycle. On their posters they represented the processes by which carbon moves and changes form: photosynthesis, respiration, decomposition, calcification, and combustion. Even though the materials as written mention climate change at every turn, I didn’t.

I finally had prepared students to think critically about the difference in carbon transfer between eating a sandwich and driving to the sandwich shop. I wondered how to broach the subject without inviting a fresh slew of emails. I knew the Keeling curve (which plots the increase in CO2 in the atmosphere), might stir things up again. Instead, I chose to show students a YouTube video from a NASA scientist who describes the similarities and differences between coal and a banana. The friendly scientist, who introduces himself as Peter, explains that both coal and bananas capture atmospheric carbon via photosynthesis, but that the banana stores carbon in a short cycle involving digestion that lasts a few months at most, while coal stores carbon in a long cycle suddenly released when burned for energy. That afternoon, I got a new email from Trevor’s dad.

He suggested that I use a Wall Street Journal article about the growth of an isolated population of polar bears as proof that all was well in the Arctic. He thought I could use it to frame a class debate on whether or not climate change was happening at all. I responded: Students were learning about the carbon cycle in a way that would have them much more actively involved in learning science than they would be through a series of discussions about climate change. In my own mind I wasn’t sure if banning discussion (and consequently the trigger phrase “climate change”) was such a good idea, but since he didn’t reply I figured no news was good news.

After comparing coal and bananas, our study of the carbon cycle culminated with a look at the human impact on the transfer of carbon. Students worked in groups to represent the impact on their posters. Examples included cement manufacturing, which moves carbon from the lithosphere to the atmosphere, and cattle farming, which shifts carbon from the biosphere to the atmosphere. They also included the impact of deforestation (biosphere to atmosphere), auto emissions, and burning coal for electricity (lithosphere to atmosphere.)

In order to know how well students were grasping the closed nature of the carbon cycle as well as human modifications to it, I asked them to respond in writing to the following questions:

  • Are humans adding more carbon to the carbon cycle? Why or why not?
  • What are human beings doing to change the carbon cycle? Give two examples.
  • What is the difference between the short (fast) and long (slow) carbon cycle? Does the difference between bananas (fast carbon) and coal (slow carbon) matter? Why or why not?
  • Do you think human alterations of the carbon cycle matter? Why or why not?

I was surprised by how difficult it was for my 6th graders to grasp that, in spite of the increasing carbon in the atmosphere, the net planetary carbon remains stable. I suspect students struggle with the concept of a closed carbon loop because carbon alone is never visible. We see carbon only at rest in a seashell, the flesh on our bones, the leaf on a plant, or the dark rock of coal. The problematic carbon is in gas form. My consistent message was “A finite amount of carbon cycles through this closed system.” I didn’t say a word about the climate and, to my relief, the doubting dad stayed quiet and Trevor remained relaxed.

Although a few students held onto the misconception that more carbon in the atmosphere means more carbon on Earth, I could see that they all understood that eating a banana and burning coal—while both transfer carbon to the atmosphere—affect the Earth in significantly different ways. Faye wrote: “We are releasing too much slow carbon from the lithosphere too fast for the biosphere to drink it up.” Meera conveyed a nuanced understanding: “I’m not sure if humans by themselves are a problem. I don’t think breathing is bad . . . but our factories and cars are really big problems since they pollute so much.” And Trevor was learning, too. He wrote: “I think that human alterations of the carbon cycle are a problem but not a problem. I believe that we shouldn’t pollute and release bad gases, but I think there is a reason we’re able to breathe and have carbon go into the air and not ‘destroy’ the Earth. There are trees and an ocean and all the things that eliminate carbon from the air.”

With students’ emerging understanding of the short and long carbon cycles, I wanted to bring them back to climate change—the reason we were talking about carbon in the first place—and, given their strong feelings, what to do about it. We were only weeks from the end of the school year and I hadn’t taught in depth about mining tar sands, coal mining, and the fracking process used to extract natural gas. Sadly, I knew I wouldn’t have time to do the topics justice and still plan an action.

In changing my plans in order to address Trevor’s dad’s complaints, I had spent too much time in the apolitical scientific realm of the carbon cycle to adequately connect excess atmospheric CO2 to human behavior. When I asked students what they’d like to do, the notion of fighting major industrial sources of excess CO2 was conspicuously absent. Because they had learned the science without referencing climate change, they didn’t know nearly enough about what it had to do with 21st-century living.

The next time I teach the carbon cycle, I hope I can achieve the same depth of scientific knowledge while using the term climate change, without throwing a child into a crisis because what he hears at home is so different. This time, however, I was glad that at least everything on my class’ list of possible actions was connected to the carbon cycle. They included the impossible (hold your breath, stop eating, and the inevitable for early adolescents—stop farting) as well as the possible (drive less, turn off our computers, and plant some trees).

As the school year ended, the class participated in the joyful planting of a fast-growing carbon-absorbing maple tree, which they named Murphy Edgar Wood. On the last day of school, with lockers clean, books turned in, and desks pushed aside, my class held an appreciation raffle. Every student submitted an appreciation of someone in the class. With each draw, there were two winners: the one who wrote the appreciation and the one receiving it. Alec wrote his to the tree: “Dear Murphy Edgar Wood. Thank you for sequestering carbon on our campus. I am very appreciative of you reducing the greenhouse effect.”

Although that little tree may not be much, I hope it symbolizes the fact that moving carbon from the long carbon cycle to the short one is not inevitable. I want my 6th graders to remember that we make choices as we interact with the Earth. I want them to remember that in planting Murphy, they took collective action and worked together to make a difference. They are young, and they will encounter climate change again and again in their lifetimes. Perhaps with their objective knowledge of the carbon cycle, they will engage the logic of those who say the wholesale transfer of carbon from earth to sky is nothing to worry about. Moreover, when the coal trains threaten again to come through town—as they will—students will know why so many of our citizens picket and they’ll have a scientific basis for choosing whether to join in on the action.


Jana Dean ( teaches 6th graders at Jefferson Middle School in the Olympia School District. Student names have been changed.

Artist Erik Ruin’s work can be viewed at