Wednesday, November 12, 2014

A Carbon Ghost Follows Me Around

I keep trying to think of ways of conveying to my students the magnitude of our human impact on the Earth in some form that they can understand. I have my botany students calculate their annual carbon footprints, and the amount of carbon dioxide a tree might absorb during a year (based on their actual estimates of the leaf area of a tree). They are briefly astonished at the number of trees that it would take to offset their carbon production. I think this works, but I get the feeling that they just go through the calculations (which even science majors do incorrectly) and then forget all about it.

Let me try something new. I don’t know if it will help, but I can give it a try.

First, I calculated my carbon footprint, using The Nature Conservancy calculator. Their estimate of my carbon production (31 tons a year) exceeds that of the average American (27 tons) I suspect mainly because I do a lot of driving, even though it is with a small car. The world average is 5.5 tons. This is in CO2 equivalents; that is, the CO2 used to manufacture items, grow and process food, and run power plants.

Second, I calculated the amount of carbon dioxide I breathe out. According to one online estimate, a person breathes out 350 kilograms of carbon dioxide a year. This would be about 0.3 metric tons, which is pretty close to English tons.

That is, I produce a hundred times as much CO2 by my activities as I do by breathing. I can therefore try to imagine that, wherever I go, a ghost a hundred times my size is following me around emitting carbon. That is, a hundred times my volume; it would be about 4.6 times as tall, as wide, and as thick. My pet carbon-ghost, chained to me day and night. Maybe a creepy image, buy possibly one that I can use for myself and for my students. I can have them calculate their carbon footprints in tons per year, divide by 0.3, and this is their carbon-ghoul.

I tried this as an extra credit assignment for my students. Many of them did it, since it was quick and easy. I do not know how many of them really thought about the image that they produce a hundred times as much carbon emissions by what they do as by breathing out.

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