Clicker quiz: Carbon and the climate created by Sarah Wise, CIRES Education and Outreach, for use by faculty at U. of Colorado at Boulder for Focus the Nation, Jan. 31, 2008 Faculty: Take these slides as suggestions, feel free to modify to your class’s needs.

1. Which cycle does this diagram represent? a. Carbon b. nitrogen c. water d. phosphorous Answer: a. carbon Source of Diagram: The Blue Planet, Skinner et al., 1999

1. Follow up discussion: What clues from the diagram did you use to choose your answer? Students may say that it must be carbon because 1) it is emitted from fossil fuel burning, 2) it is taken up by photosynthesis, 3) it is given off by respiration, 4) it is stored in fossil fuels, 5) it is dissolved in water, 6) it is stored often as calcium carbonate in sediments and rocks, 7) it is stored as sugar and carbohydrates in plant matter.

2. How do human activities affect the carbon cycle? add pollution to the cycle add carbon to the cycle transfer carbon from earth to atmosphere cause the cycle to slow or stop Answer: c. transfer carbon from earth to atmosphere..

2. Follow up discussion: Why are all but c. incorrect? add pollution to the cycle add carbon to the cycle transfer carbon from earth to atmosphere cause the cycle to slow or stop Other answers represent misconceptions about the carbon cycle. Rates of the cycle are driven by physical processes. The law of conservation of matter means that carbon cannot be added, only moved. Pollution is a catch all term; while fossil fuel burning does add pollutants such as air particulates into the atmosphere, those pollutants do not “add” to the carbon cycle.

3. What do these two graphs show? CO2 increase is causing warming b. CO2 increase is strongly correlated with warming The answer is b. CO2 increase is strongly correlated with warming. The top graph is the Keeling curve. The red oscillating line follows seasonal fluctuations in carbon dioxide levels. Carbon dioxide decreases in the summer, as plants photosynthesize, and increases in the winter, as plants and animals contribute a net flux of carbon dioxide to the atmosphere through respiration. source of diagrams: Wikipedia: Keeling curve, global warming

what is different between correlation and causation? 3. Follow up discussion: what is different between correlation and causation? A short answer is that a correlation occurs when two things appear to vary together. To show causation between two things, there needs to be a logical mechanisms that links the two. These graphs show a correlation, but more information is needed to explain why the two are correlated (the mechanism). source of diagrams: Wikipedia: Keeling curve, global warming

4. What do these diagrams suggest about the cause of global warming? Answer: c. both a. and b. Faculty showing this slide may want to review the mechanism of the greenhouse effect in order to fully describe how the greenhouse effect is the best explanation for the observed warming trend, and its correlation with increased CO2. You may also want to review the measures used for solar cycle variation – what the difference is between irradiance, 10.7 radio flux, sunspot observations, and the solar flare index. But you can also simply point out that four independent measures of solar input give a similar pattern that is not correlated with increased warming over the last 30 years. increased greenhouse gases (e.g. CO2) can cause warming b. natural variation in the sun is not correlated with recent warming c. both a. and b. source of diagrams: Wikipedia, global warming

4. Follow up: Has anyone learned about other possible explanations of warming, based on known causes? Faculty: if you choose to use this follow up question, it would be good to review a variety of possible contrarian arguments that student may bring up as what they have learned about. See: http://gristmill.grist.org/skeptics

Discussion questions: -- is there a difference between global warming and climate change? -- how do you think climate change will affect your life? -- how do you think the problem of climate change may be resolved? -- what do your friends and family think about climate change? -- has the issue of climate change made you want to make changes in your life? Faculty: again, please feel free to modify for use with your specific class. Note that research shows that introducing climate change without providing some time for discussion of solutions can leave people with “doom and gloom” – a feeling that may make them less likely to act on the information.