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Free Carbon Matters
Middle school students get carbon cycle literate

By Jana Dean


Home > Archives > Volume 28 No.4 - Summer 2014

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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.”



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