Climate Change? The Modern CO₂ Record

Modern CO₂ Record Measurements

In this lab, we will focus on the levels of atmospheric carbon dioxide (CO2) that scientists have measured at permanent observatories at Mauna Loa (Hawai’i), Barrow (Alaska), and the South Pole. We will use these data to investigate

(1)   processes that might control variations in atmospheric CO2 levels during the year, and

(2) processes that might explain the long-term trend in atmospheric CO2 levels.

We will also briefly at another greenhouse gas that may contribute to climate change.

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In 1958, scientists (notably Professor Charles Keeling) began to use high-precision equipment (e.g., infrared analyzers) to measure the abundance of atmospheric CO2 at selected sites around the globe. Among the initial sites were Mauna Loa, a 13,000-foot mountain on Hawai’i, and a station just a few miles from the South Pole. Measurements were begun at later times at other stations (e.g., 1973 for Barrow).

1. Familiarize yourself with the locations of these three measuring stations:

2. Examine the three graphs below. The curve on each graph connects monthly measurements, though it’s difficult or impossible to see the points for individual months at this scale.

A. What is the variable being measured? Click or tap here to enter text.

B. What units are used to express this variable? Click or tap here to enter text.

C. In your own words, express what this means (https://en.wikipedia.org/wiki/Parts-per_notation)

              Click or tap here to enter text.

3. Although none of the graphs below showing average monthly CO2 concentration increase from 1958-2004 are a perfectly smooth curve, all of them show the same long-term pattern. Describe this pattern in 1-2 sentences.

Click or tap here to enter text.

4. The numbers below show the monthly (numbered 1 (Jan) through 12 (Dec)) readings for the years 2003 and 2004 at each station. The last column is the annual average. Plot the 2004 results from all three stations on the same graph on the next page. Connect the points for each site with a smooth curve and label each curve with the site name. You can also do this in Microsoft Excel.

Each of the three curves should clearly show a cycle known as a short-period oscillation (movement back and forth in a sequence). You would have received nearly identical curves if you’d graphed the 2003 data instead, because the curves have 12-month periods (i.e., 12 months from peak to peak or from trough to trough).

Our goal is to determine the cause of these short-period oscillations. Let’s analyze some aspects of these three curves.

5. First, in what month are the maximum and minimum values recorded at each station?

Click or tap here to enter text.

6. What is the amplitude of the oscillation? In other words, what is the difference (in ppm CO2) of the maximum and minimum value over the whole year at each station?

Mauna Loa minimum: Click or tap here to enter text.ppm     

Mauna Loa maximum: Click or tap here to enter text.ppm     

Mauna Loa amplitude: Click or tap here to enter text.ppm     

Barrow minimum: Click or tap here to enter text.ppm   

Barrow maximum: Click or tap here to enter text.ppm   

Barrow amplitude: Click or tap here to enter text.ppm   

South Pole minimum: Click or tap here to enter text.ppm

South Pole maximum: Click or tap here to enter text.ppm

South Pole amplitude: Click or tap here to enter text.ppm

7. Interpret your results (in terms of the geographic locations of the three sites) to answer the following questions.

A. Why do the oscillations occur (Hint: you may want to research photosynthesis and respiration)?

 Click or tap here to enter text.

B. Why do the oscillations peak when they do – how does yearly change in seasons relate to the oscillations?

Click or tap here to enter text.

C. Why is the amplitude of the South Pole station so much smaller than that of the other two?

Click or tap here to enter text.