Academic journal article The Science Teacher

Finding the C[O.Sub.2] Culprit: Investigating Whether Man or Mountain Emits More Atmospheric Carbon Dioxide

Academic journal article The Science Teacher

Finding the C[O.Sub.2] Culprit: Investigating Whether Man or Mountain Emits More Atmospheric Carbon Dioxide

Article excerpt

In 2013, the Intergovernmental Panel on Climate Change released its fifth report, attributing 95% of all climate warming--from the 1950s through today--to humans (IPCC 2013). Not only did the report--like previous IPCC reports dating back to 1990--accredit global warming to anthropogenic carbon dioxide emissions, but over time the vast majority of scientists have endorsed this view of human-caused climate change (Cook et al. 2013; Oreskes 2004). Still, we meet many students who question whether climate change is real, whether it is part of a natural cycle, and whether other sources besides humans may be responsible.

To compare the role of natural Earth processes in C[O.sub.2] emissions with humans' role, we designed a student research investigation described in this article. Students graph volcanic and human components in C[O.sub.2] emissions, analyze their results, and then can compare their results with those in peer-reviewed scientists' reports.

Climate change to the forefront

After the IPCC released its fourth assessment report in 2007, we saw the climate issue move to the forefront of media attention and classroom discussions of our students (Clary and Wandersee 2012a). In 2009 came "Climategate," in which hacked e-mails from climate scientists at England's University of East Anglia brought into question scientists' impartiality and research ethics. Although later investigations exonerated the scientists of illegal behavior (Oxburgh 2010; Russell et al. 2010), members of the public remained skeptical (Leiserowitz et al. 2013).

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Meanwhile, some climate-change skeptics suggested that volcanoes emit more C[O.sub.2] than human activities. A volcano (Figure 1) can produce three phases of materials: solids (pyroclastics), liquids (magma/lava), and gases (water vapor, C[O.sub.2], and sulfur gases). The C[O.sub.2] and other gases are emitted as the volcano's magma degasses.

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How does the volcanic C[O.sub.2] contribution compare to the anthropogenic one? Fortunately, a U.S. volcanologist calculated human and volcanic effect on C[O.sub.2] production (Gerlach 2011). Summerhayes (2011), of Scott Polar Research Institute, furthered the investigation to find the source of greenhouse gases. Results of these investigations showed that modern volcanoes annually emit only as much C[O.sub.2] as states like Florida, Michigan, or Ohio (Gerlach 2011).

A student investigation

Using data reported by Gerlach (2011) and Summerhayes (2011), from both direct monitoring and computer modeling, we designed a student investigation into the source of C[O.sub.2], comparing volcanic emissions to those produced by human activity, and whether humans should accept the responsibility that the IPCC (2013) attributed to us. The graphical representation of authentic data augments the peer-reviewed articles we bring into the classroom and provides students with the "aha!" moment in their understanding of the issue. If needed, teachers can assess incoming student knowledge with a published Climate Change Survey (Clary and Wandersee 2012a, 2014).

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To begin the inquiry, we announce that students will investigate and compare two sources of C[O.sub.2,], the greenhouse gas most implicated in global climate change. Beside water vapor, our atmosphere consists primarily of nitrogen ([N.sub.2]), at 78%, and oxygen ([O.sub.2]), at 21%. Carbon dioxide makes up only 0.04% of the atmosphere by volume yet is still the gas most associated with the greenhouse effect. (Often, C[O.sub.2] levels are reported in parts per million [ppm]. Concentrations in ppm can be calculated by multiplying the percentage of volume by [10.sup.4]. That gives us a current concentration of atmospheric C[O.sub.2] of approximately 400 ppm.)

What are the sources of C[O. …

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