Carbon In the Atmosphere
Part C: Keeping track of CO2 in today's atmosphere
In Lab 3B, you observed that changes in the global carbon cycle can operate at very long time scales associated with past ice ages. In this section, you will investigate recent trends in changes in atm CO2 over much shorter time scales of years to decades. First, take a few minutes to examine the graph on the right. Click to enlarge.
How does the current trend of atm CO2 since 1950 compare to atm CO2 over the past 650,000 years?
Variations and trends are important patterns that scientists look for in complex systems
Long-term time series data are important to scientists who study complex systems such as climate and the carbon cycle. Time series data taken at equal time intervals often generate important trends that help explain the behavior of a system over time. Scientists use trends to understand the past, the present and to predict the future. Long-term trends can emerge from data that is often quite variable and operates at very different time and spatial scales. You have already seen examples of this variability when you analyzed CO2 and temperature data from the Vostok ice cores.
To help you understand the difference between trend and variation, watch the video below:
Watching Earth Breathe: Seasonal changes in vegetation and CO2
Different components of a complex system such as the carbon cycle can operate over many different time scales and spatial scales. For example, NASA has detected seasonal changes in atm CO2 concentration measured by AIRS and in vegetation growth measured by another instrument on the Aqua satellite called MODIS. NASA has used the data from AIRS and MODIS to create a year long animation of these seasonal changes in CO2 and vegetation. Before you watch the NASA animation below, make note of the following:
- CO2 in the atmosphere is represented by the color orange. The deeper the orange, the greater the amount of CO2.
- Changes in vegetation growth is represented by the color green. The deeper the green, the denser the vegetation.
- You can pause the animation by clicking on the date (example SEPT 01) or by clicking pause.
- It helps to first pay careful attention to what the vegetation is doing and then pay attention to what CO2 is doing.
- Remember that vegetation and photosynthesis are linked.
With a group or with the class, discuss the following:
- What patterns in atm CO2 and vegetation over time can you observe in this animation? List all that you can.
- On what time scales are the changes in atm CO2 and vegetation changing?
- How do the spatial scales of atm CO2 and vegetation differ between the Northern Hemisphere and the Southern Hemisphere? What might account for those differences? Hint: Think about differences in land mass.
- Explain how a seasonal change in vegetation and photosynthesis can drive a seasonal change in levels of atm CO2.
- Did you observe any long-term trend(s) in concentrations of CO2 in the animation?
Mauna Loa Observatory
The Keeling Curve reveals seasonal patterns and a decadal trend in atm CO2
As the leading greenhouse gas, atm CO2 is the most closely studied and measured gas in our atmosphere. In the 1950s, the United States Air Force studied atm CO2 as part of their Cold War missile program. In 1958, regular measurements of atm CO2 began when a young geochemist named Charles Keeling collected and analyzed samples of CO2 on top of the Mauna Loa volcano on the Island of Hawaii in the Pacific Ocean. When analyzing his atm CO2 data, Dr. Keeling discovered some interesting patterns in CO2 and a worrisome trend. Watch the video below on Charles Keeling and his data. As you watch, pay attention to the pattern of variations in CO2.
Next, use the animation below to investigate Keeling's atm CO2 data in greater depth. As you go through the animation:
- Keep in mind what you have already learned about the seasonality of the carbon cycle and its relationship to vegetation and photosynthesis.
- At the end of the Animation there is a More Info screen where you will find hints to understanding Dr. Keeling's data. You can also find a link to the most recent monthly average CO2 data measured from Mauna Loa below.
- atm CO2 is measured in ppmor 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.
With a peer or group, discuss the following:
- Describe the pattern of variations that emerged from Keeling's CO2 data. Did you see these same types of variations in the NASA animation of seasonal CO2 and vegetation? Explain.
- Describe the time series trend of atm CO2measured at Mauna Loa. What does this trend "say" about the concentration of atm CO2 since 1958?
- What evidence, if any, does Keeling's data provide that the carbon chemistry of our atmosphere is changing?
- The Keeling Curve represents atm CO2 data taken from the top of the Mauna Loa volcano in the Hawaiian Islands. Because of this, some people on the Internet have claimed that Keeling's data is influenced by CO2 released from the nearby volcano. Does the rise in atm CO2concentration over Mauna Loa represent a trend only on a regional scale or on a global scale? What makes you think so?
Using ESRL's CarbonTracker program to measure trends and variations in levels of atm CO2 around the world
The Keeling Curve CO2 data indicates that the amount of atm CO2measured at the Mauna Loa Observatory has been increasing since 1958, the date of the first measurement taken by Charles Keeling. Is this same trend occurring elsewhere in the world?
Laboratory Investigation: Instructions
In this investigation, your group will use CarbonTracker to generate graphs of atm CO2 data measured from different sampling locations around the world. You will compare these graphs to each other and to Mauna Loa data to look for differences and similarities in trends and variations.
- Before you begin your investigation, it is important to spend some time familiarizing yourself with the CarbonTracker tool.