Communications Booster: Exploring Regional Differences in Atmospheric CO₂ Concentrations

Anna Lewis, University of South Florida
Jon A. Leydens, Colorado School of Mines
Julie Lambert, Florida Atlantic University

Component of this Activity from the CLEAN Reviewed Collection:
Using a mass balance model to understand carbon dioxide and its connection to global warming by Robert MacKay

Key Learning Outcomes
In the existing activity, students learn about recent trends in atmospheric carbon dioxide using an online model, which allows them to estimate present emission and emission growth rates as well as future CO₂ levels using different emission scenarios. Students then link these different scenarios to IPCC climate model predictions. Students may wonder about regional variations, so our activity adds a dimension by allowing students to bolster their understanding of regional CO₂ trend variations within an overall global CO₂ trend.

Climate Literacy Context
Both the initial and supplementary activities connect to several core climate literacy topics: greenhouse effect, carbon cycle, greenhouse gases, greenhouse gas emissions, and climate projections. The supplementary activity adds an additional topic: local vs. global GHG emission trends.

The topic is important in rebutting the misconception and myth noted below, especially in terms of understanding how local CO₂ trends fit within a larger global trend.

Misconceptions and Potential Pitfalls
As noted above, this extension topic is important in rebutting the following misconceptions:

• A global trend of increasing atmospheric CO₂ means that all local regions are also seeing the same increasing trend;
• A decline in CO₂ locally weakens the well-established claim that global CO₂ is increasing significantly;
• Students may assume that since the atmosphere covers the Earth, CO₂ levels in one location would experience the same rate of change and levels of CO₂ as in other geographic locations.

Instructional Strategies
Begin this activity with a short discussion that will bring students' attention to their current understanding of certain concepts. In groups, ask students to discuss and write down their answers to the following questions:

1. We saw earlier that CO₂ levels in Mauna Loa have been rising over time, does this mean CO₂ levels are also rising everywhere else in the world?
2. If yes, does this mean CO₂ levels are rising at the same or different rate(s) everywhere else in the world?
3. If no, why would CO₂ levels be rising only in Mauna Loa?

Have each group briefly share their answers with the class. You may wish to ask students to clarify their responses to better understand the group perspective. However, do not address any misconceptions or correct students at this time; wait until data has been gathered and analyzed to revisit these issues.

Next, to expand upon the concepts studied in the original activity, provide students with similar data from different observatories from around the world. This can be obtained from the ESRL Global Monitoring website (website and selected data sets are shown below). Students may copy these text files into an Excel sheet and graph CO₂ concentrations over time by monthly annual averages. Use the Supplemental Materials assignment below to guide this activity.

On a whiteboard, wall, or overhead slide display a world map and empty matrix. As each group completes the annual averages table, have one person from each group locate and mark their observatory on the map and add their data to the class matrix; similar to the table below.

Have the student groups finish their assignment sheet comparing their data with the Mauna Loa data. Discuss their findings from the assignment sheet and their observations regarding the class matrix. What do they notice? This should provide a rich class discussion. Next, revisit the initial questions that were asked at the beginning of the lesson. Have the students discuss in their groups how they would answer those questions now that they have analyzed additional data; are their responses the same or different? As each group reports their experiences and understandings, the facilitator can direct students to the wealth of data that they have collected to assist in dispelling any myths that may have surfaced and have persisted.

After this discussion, the facilitator may wish to show students an animation from NOAA that illustrates global CO₂ levels over time and regions. This animation shows the "zig-zag" over a year period and shows students that the level of carbon dioxide decreases slightly during the Northern Hemisphere's spring and summer months. This animation also shows that the current level of atmospheric carbon dioxide is the highest level during the past 800,000 years. See http://www.esrl.noaa.gov/gmd/ccgg/trends/history.html.

Once students have observed and discussed the empirical evidence of how different geographic locations experience different concentrations of CO₂ and also different rates of change of CO₂ concentrations, the next question to tackle is why these differences exist.

By better understanding the carbon cycle, causes may be determined. The following links How do Human Activities Contribute to Climate Change and How do They Compare with Natural Influences? and the EPA Greenhouse Gas Emissions page may be helpful in exploring carbon and other greenhouse gas emissions to identify sources and sinks or absorbers of atmospheric gases. A key fact is that there is more land in the Northern Hemisphere and more trees photosynthesizing during the spring and summer which impacts the carbon cycle compared to the Southern Hemisphere. This is one of several reasons that the atmospheric carbon dioxide concentrations are often lower during the Northern Hemisphere's spring and summer months.

Supplemental Materials
This supplemental activity can be used in conjunction with the mass balance activity to round out students' understanding.

Use this web page to find specific data files available from the public ftp file archive of the ESRL Global Monitoring Division. The data sets below provide you with a variety of locations around the globe that have 30 years or more of data to analyze. The data sets are text files that provide: Year, Month, and CO₂ concentrations measured at the specified observatories. These data may be copied directly into an Excel spreadsheet and used to create similar graphs as found in the original activity. All data sets below come directly from the ESRL Global Monitoring website.

1. Ascension Island, UK [1979-2010]
2. Terceira Island, Azores, Portugal [1979-2010]
3. Barrow, Alaska, US [1971-2010]
4. Mariana Islands, Guam [1979-2010]
5. Key Biscayne, Florida, US [1972-2010]
6. Mould Bay, Nanavut, Canada [1980-1997]
7. Niwot Ridge, Colorado, US [1968-2010]
8. Pacific Ocean, 0 degrees North [1987-2010] (Note: There are stations that collect data from 0 degrees North to 25 degrees North at 5 degree intervals and 5 degrees South to 35 degrees South at 5 degree intervals. Another interesting class activity could be to use these data sets to observe CO₂ changes along a single latitude)
9. Pacific Ocean, 5 degrees South [1987-2010]
10. Palmer Station, Antarctica, US [1978-2010]
11. Mehe Island, Seychelles [1980-2010]
12. Tutuila, American Samoa [1978-2010]
13. South Pole, Antarctica, US [1978-2010]
14. Ocean Station M. Norway [1981-2010]

Here is one possible supplemental assignment format:

Carbon Dioxide Levels over Time

What region did you gather data from:______________________________

Paste your graph in the space below (make sure to include units, axis labels, and a graph title):

Q1: How has the CO₂ concentration changed over the recent past in the location you just graphed?

Q2: What are the approximate annual average concentrations of CO₂ in 1970, 1980, 1990, 2000? (not everyone will have data for each decade; simply enter averages for the data you have available)

×

Q3: From these estimated values, is the rate of increase of CO₂ in your location: (circle one)

Growing | Staying about the same | Decreasing

Q4: Compare your data with the Mauna Loa data for CO₂:

Explain how they are different and how they are the same. Offer some suggestions as to what might explain the differences or similarities found in the data. Describe how you might support your ideas (i.e. what additional data would you require to prove or disprove your ideas).

References

The Carbon dioxide exercise by Randall Richardson, is also related to this topic and could be taught in conjunction with these themes.

The following article, Assessing Elementary Science Methods Students' Understanding About Global Climate Change, may be of interest regarding teacher preparation in teaching climate science.