EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 3: Carbon in the Atmosphere > 3B: My Life's Story

# Carbon In the Atmosphere - My Life as a Greenhouse Gas

## Part B: Carbon Dioxide - My Life's Story

Imagine if fossils didn't exist. How would we know that dinosaurs, woolly mammoths and other long extinct creatures once roamed the Earth and swam in our oceans. Like fossils, carbon dioxide has left it own set of "fingerprints." These fingerprints serve as clues to past climates and possibly to future climates.

Consider the graph on the right. (click to enlarge). The graph shows "fingerprints" of carbon dioxide and temperature of the past six ice ages and interglacial periods that have been revealed from ice cores drilled in Vostok, Antarctica.

## Discussion

Look at the various elements of the graph. The red lines represent changes in temperature over time and the blue lines represent changes in carbon dioxide over time. The peaks of carbon dioxide indicate interglacial periods. Do the "fingerprints" in this graph tell you a story of carbon dioxide and temperature over the past 600,000 years? With your partner or group, identify at least two elements of the story this graph tells you and two questions the story raises. Share your story elements and story questions with the class.

Next, listen to geoscientist, Dr. Richard Alley, explain the relationship between ice core carbon dioxide data and ice core temperature data in CO2 in the Ice Core Record Then, use information from the graph and the video to answer the Checking In and Stop and Think questions below.

## Checking In

1. Are Ice ages correlated with lower amounts of carbon dioxide (CO2) or higher amounts of CO2?

2. From 600,000 years ago to 100,000 years ago, what was the highest concentration of carbon dioxide(ppm)

3. The carbon cycle can change on vastly different time scales. Carbon dioxide data from the Vostok ice cores provides evidence for the carbon cycle changing on time scales of?

## Stop and Think

1. Describe the relationship between carbon dioxide, temperature and ice ages.

### × Watching the Earth Breathe: An Animation of Seasonal Vegetation and its effect on Earth's Global Atmospheric Carbon Dioxide Seasonal changes in the carbon cycle: NASA satellites see the Earth "breath."

You have already seen that changes in the global carbon cycle can operate at very long time scales associated with past ice ages. Different components of a complex system such as the carbon cycle can change over many different time scales and spatial scales. For example, the AIRS and MODIS instruments on-board two NASA satellites have detected carbon cycle changes in atmospheric CO2 and vegetation growth that happen in seasonal time scales and at a hemispheric spatial scale. Scientists have used the CO2 and vegetation data collected from the AIRS and MODIS instruments to create the animation Watching Earth Breathe: The Seasonal Vegetation Cycle and Carbon Dioxide.

Before using the animation, make note of the following:

• CO2 in the atmosphere detected by AIRS is represented by the color orange. The deeper the orange, the greater the amount of CO2.
• Changes in vegetation growth detected by MODIS is represented by the color green.
• Click on the date (example SEPT 01) to stop the video at various points throughout the year. Note: You can also do this by clicking pause.
• View the animation completely and make note of trends in CO2 and vegetation over one year. Then, return to the beginning and stop the animation at different months to get a deeper understanding of what changes in CO2 and vegetation are occurring in different months and seasons of the year. Don't forget to pay attention to differences in CO2and vegetation changes in the northern hemisphere versus the southern hemisphere. Note: The timing of seasons is reversed in the two hemispheres. For example, when it is winter in the northern hemisphere, it is summer in the southern hemisphere.
• Answer the Discussion questions below.

Note: This animation can also be viewed at the following sites:

## Discussion

1. Which hemisphere seems to produce the greatest amount of carbon dioxide? Why do you think this is so?
2. In what months do the levels of atmospheric CO2 increase in the Northern hemisphere? What is happening to the vegetation when CO2levels are increasing?
3. In what months do the levels of atmospheric CO2 decrease in the northern hemisphere? What is happening to the vegetation when the CO2 levels are decreasing?
4. What role do you think photosynthesis plays in the seasonal changes in CO2 you have observed in the animation? Why?
5. What differences in levels of atmospheric CO2 and vegetation do you see in the northern hemisphere versus the southern hemisphere? What might account for these differences?
6. If you were asked to draw a graph illustrating seasonal changes in atmospheric CO2 levels over the course of ten years, what would the shape of the graph look like? Draw one and compare your graph with graphs drawn by other groups. Which graphs most accurately illustrate seasonal changes in the global carbon cycle over a ten year period? Then, keep this graph handy as you investigate a famous graph of atmospheric carbon dioxide over time - the Keeling Curve.

### The Keeling Curve: Is our atmosphere changing?

In the late 1950s, Dr. Charles Keeling started measuring CO2 levels on top of the Mauna Loa volcano on the Island of Hawaii in the Pacific Ocean. He chose this location because he wanted to take measurements far away from urban areas that are emitting man-made CO2 into the atmosphere. Because winds and convection currents move carbon dioxide around Earth's atmosphere, it was possible for Dr. Keeling to take global measurements of CO2. Sometimes called the Keeling Curve, this graph represents the longest running global atmospheric CO2 data on record and is one of the most recognized iconic graphs in science.

Use the interactive below to investigate Keeling's atm CO2 data from Mauna Loa. As you go through the interactive, keep in mind what you have already learned about the seasonality of the carbon cycle and its relationship to vegetation and photosynthesis. If you click on the "more info" button, you will find hints to understanding Dr. Keeling's data. When you finish, answer the discussion questions below: Note: You will need FLASH

## Discussion

1. According to Keeling's atm CO2 data, how much has the amount of atm CO2 changed from his first measurements in 1958 to measurements taken in 2012. Note: atm CO2 is measured in ppm - or parts per million per volume. Watch this visualization of 392 ppm of carbon dioxide molecules compared to nitrogen and oxygen molecules in the atmosphere to help you understand ppm.
2. Compare and contrast the Keeling Curve graph to the graph you previously drew. What is similar and what is different? Why do you think it is different?
3. What evidence does Keeling's data provide that the atmosphere is changing?
4. The Keeling Curve measurement of atmospheric CO2 is taken from the top of the Mauna Loa volcano in the Hawaiian Islands. Is this one dataset, taken from only one location in the world, enough for scientists to claim with confidence that the levels of global atmospheric CO2 are increasing? Why or why not?

### Atmospheric CO2 levels from around the world.

When trying to understand complex systems, such as the carbon cycle or the Earth System, scientists will often compare multiple data sets to identify possible relationships and trends. When other scientists first observed Dr. Keeling's CO2 data, they immediately looked for ways to confirm the data. Would they see the same trend in increasing atmospheric CO2 if they collected CO2 measurements in different locations and used different collection methods?[narrowimage 57787 right border caption] Interactive Atmospheric Data Visualization (IADV). NOAA. Click to enlarge.

You may find the answer to this important question by using CarbonTracker, a program developed by The Earth System Research Laboratory (ESRL) in Boulder, Colorado and operated by the National Oceanic and Atmospheric Administration(NOAA). ESRL studies processes that affect the atmosphere, air quality, and weather and climate. ESRL's CarbonTracker program collects all the data from greenhouse gas measurements taken from around the world and puts it into the Interactive Atmospheric Data Visualization(IADV) database that scientists and non-scientists can access at any time. Open Carbon Tracker: Interactive Atmospheric Data Visualization(IADV)Tool and and spend some time exploring to see what type of information is available.

Show me the steps to explore the IADV Carbon Tracker interactive.

1. Explore the interactivity of the IADV Carbon Tracker program. Click on the measurement sampling sites represented by different colored dots. What information pops up? What do the yellow, red, orange and blue colors of the dots tell you about the measurement sites?

2. Find the the Mauna Loa site. Make note of the following information that pops up:

• What is the latitude and longitude of the Mauna Loa measurement site?
• What is the elevation? (masl = meters above sea level)
• Look for the carbon cycle gas measurements that they measure at Mauna Loa. What types of measurements do they take (tower, airborne flask, surface flasks, in-situ ).
• Are the measurements taken from land, boat or plane?

3. Next, explore other measurement sites? How do they compare to Mauna Loa?

4. Drag the map from left to right or right to left to target particular countries or area of the world.

5. Zoom in to a particular country or area of the world. What measurement site is closest to where you live? What type of data does this site collect?

6. Go back to the Mauna Loa site.

7. Find the "Program" Tab above the map. Open that tab and Click on "Carbon Cycle Gases." This action will allow you to see only those measurement sites that collect carbon cycle gas data.

8. Next, move over to the menu to the left of the map. Click on "Carbon Cycle Gases" and then click on "Time Series." This will bring you to the Keeling CO2 Data from Mauna Loa. You should see an image that looks like the image on the right.

• Parameters - carbon dioxide (CO2)
• Data Type - Choose Flask or In-Situ. Many sites will only have one type. Click "Submit" if you change from one to another
• Date Frequency - Ignore and leave at "discrete."
• Time span -Choose "All" This will give you a graph of all the data collected to date. If you would like to explore shorter data sets, you can choose "start year" and "end year" and click "Submit" to see the graph.

## Checking In

1. When you explored the Mauna Loa measurement site on CarbonTracker, you were asked to keep notes on the information available to you. Use those notes to answer the following question: Which of the following are correct statements about the Mauna Loa sampling site and the CO2 data this site collects? Check all that apply.

2.

### Use Carbon Tracker and begin your own research

The Keeling Curve CO2 data indicates that the amount of carbon dioxide in the atmosphere has been increasing at least since 1958, the first time atmospheric carbon dioxide was measured at Mauna Loa. Are the same trends in atmospheric CO2 observed in other measurements taken around the world?

Use the CarbonTracker IADV to answer the research question above. Examine carbon dioxide time series data from at least three sampling sites around the world taken. Describe the overall trends of CO2 at each site. Then, compare CO2 trends from these sampling sites with the Keeling CO2 data from Mauna Loa. Note: The yellow dots represent sampling stations no longer collecting data and should not be used in your investigation.

Choose a CO2 measurement variable:
In your exploration of the CarbonTracher IADV site, you learned that there are many CO2 measurement variables you can explore. You may choose one variable (example: measurements taken on land) or you may decide to compare variables (example: measurements taken on boats versus on land). Here are some examples of variables:

• Latitude and longitude: (ex) polar, temperate or tropical latitudes
• Type of measurement – (ex) tower, surface flask, in-situ
• Where measurements are taken – (ex) on land, boat, or plane
• Elevation (masl = meters above sea level)
• Countries
• Hemisphere
• Other
When you have done your research, compare the graphs and data from your CO2 sampling sites to each other and to the Keeling Curve Mauna Loa CO2 data and graph.

## Discussion

• With your partner or group, answer the research question. Do the data trends observed at your sampling sites support the same upward trend observed in Keeling curve CO2 data from Mauna Loa? What's your evidence?
• Next, share your results with the class. Do class results support or refute Keeling Curve CO2 data? What's the evidence? Are the data trends across the class exactly the same as each other or are there differences? What might account for those differences?
• Why is it important to make multiple measurements of CO2 and other gases other than just at Mauna Loa?

### Putting it all together: Temperature, CO2, the Industrial Revolution, and Fossil Fuels.

Scientists claim that CO2 levels have increased since the Industrial Revolution and that this is due primarily to the burning of fossil fuels. Furthermore, scientists claim that increasing levels of CO2 in the atmosphere are amplifying the greenhouse effect, leading to a warmer atmosphere. What's the data that supports these scientific claims?

Comparing multiple data sets can sometimes tell a more complete story than looking at one single data set at a time. Because measurements of atmospheric CO2 only began in 1958 at Mauna Loa, scientists needed to find atmospheric CO2 data and temperature data that began with the American Industrial Revolution era. Luckily, as you have learned from Dr. Richard Alley in a previous video, the CO2 trapped in ice cores can be used to give a "proxy" measure of the CO2 in the atmosphere at that time snow was laid down. Siple ice cores from Antarctica provide this CO2 data because the snow in Siple ice cores were laid down approximately from 1880-1950. For temperature data, scientists used atmospheric temperature measurements that have been taken since the mid- 1800's in the United States. To compare temperature and CO2 data and to look for trends in temperature and CO2 over time, scientists overlaid these three data sets on the graph on the right:

• Global long term temperature data 1880-2006 (Blue lines)
• Ice core CO2 data from the Siple Dome ice core, Antarctica 1880-1950 (Red lines)
• Keeling Curve CO2 data taken at Mauna Loa 1958-2006 (Yellow lines)
Show me hints to understand the graph
• There are three scales on this graph so it is important to match the correct scale with its correct data set. The time in years is the bottom scale on the x-axis.
• The scale on the left Y-axis indicates the concentration of carbon dioxide in the atmosphere and is measured in parts per million per volume (ppmv).
• The scale on the right Y-axis indicates the global temperature. Notice that the scale is in degrees Fahrenheit, not Celsius.

## Discussion

With a partner or a group, discuss the following and then share with the class.
• What trends do you see in these three data sets?
• What "story" does this graph tell you about the relationship between CO2 and temperature since the 1800's?
• Do you think the trends in the CO2 and temperature data sets will continue? What evidence from the graph supports your claim?

What is causing the increases in CO2 and temperature you have observed in the data? Are the causes natural, man-made or both? Some people on the internet have claimed that the rise in atmospheric CO2 is due to the natural process of volcanic outgassing. How do scientists know where the extra CO2 is coming from? Listen to geoscientist Dr. Richard Alley explain the science behind this very important question in the video "Its Us."

Before you watch, create a 3-column table with the following headings:

• Type of Cause.
• Evidence for this being a major cause of rising CO2 levels.
• Evidence against this being a major cause of rising CO2 levels.

As you watch the video, write careful notes in your table. When you have finished watching and taking notes, share your notes with the class. Begin watching It's Us.

## Discussion

A friend tells you that they do not believe that humans are causing the rise in atmospheric CO2. How would you explain the source of the rise of atmospheric CO2 to them?

## Stop and Think

2. Describe the overall trend in atmospheric CO2 and temperature since the 1880's.

3. Based on the current scientific data, what is causing the increases in atmospheric CO2? Describe one piece of evidence that supports your claim.

Option extensions: