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Climate Change? The Modern CO2 Record

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.

_________________________________________________________________________

 

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.

 

MLoa

1

2

3

4

5

6

7

8

9

10

11

12

Avg

2003

374.7

375.6

376.1

377.6

378.4

378.1

376.6

374.5

373.0

373.0

374.4

375.7

375.6

2004

376.8

377.4

378.4

380.5

380.6

379.6

377.8

375.9

374.1

374.2

375.9

377.5

377.4

Barrow

 

 

 

 

 

 

 

 

 

 

 

 

 

2003

379.0

382.3

381.4

381.4

382.2

380.8

371.0

364.7

368.3

372.5

378.6

382.5

377.0

2004

382.6

383.2

382.2

383.8

383.5

380.5

371.8

366.5

367.9

373.5

379.2

382.3

378.1

S. Pole

 

 

 

 

 

 

 

 

 

 

 

 

 

2003

371.9

371.8

371.7

372.0

372.3

372.6

373.0

373.4

373.9

373.8

373.6

373.6

372.8

2004

373.6

373.4

373.8

373.9

374.1

374.5

374.8

375.4

375.5

375.6

375.5

375.2

374.6

 

 

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.

 

Geologic History of atmospheric CO2 levels

Now let’s look farther back in time at atmospheric CO2 levels. Though precise measurements only began in 1958, scientists have been able to sample “fossil air” from the early 1900s and even the 1800s in tightly sealed bottles of wine of known vintage, and in old brass buttons with sealed air gaps.

 

They have also been able to sample and date fossil air in ice layers. The Law Dome ice cores in Antarctica sampled ice over a thousand years old (below).

 

The cores from Law Dome show that the amount of CO2 in the atmosphere was fairly constant from 1000 A.D. until about 1850, when it began to increase rapidly. Most atmospheric scientists attribute the increase to the emissions of CO2 from the burning of fossil fuels, which accelerated dramatically in the Industrial Revolution of the mid-1800s. However, others have suggested that

the increase is a natural phenomenon—one of Earth’s natural cycles that simply coincides with the increased burning of fossil fuels.

 

In 1998, scientists drilled a 2-mile-deep ice core at Vostok, Antarctica that gives us the CO2 record over the last 400,000 years. [Note: 400 kyr = 400,000 yr; BP = before present.]

 

 

 

 

 

 

 

The troughs on this graph correspond to Ice Ages, and the peaks correspond to the warmer interglacial periods.

8. What was the highest concentration of atmospheric CO2 during any of these interglacial periods?   

 

Click or tap here to enter text.ppm

 

9. Using the top diagram on p. 2, estimate the current average concentration of atmospheric CO2 (use the yearly average Mauna Loa data for 2004): 

 

Click or tap here to enter text.ppm

 

10. Over the last 30 years, the rate of increase of CO2 at Mauna Loa has been ~1.5 ppm/year. If this rate continues, what will the level of CO2 be in 2030 (36 years from 2004) or 2050 (56 years from 2004)?

 

In 2030 ______________ ppm        in 2050 _____________ ppm

 

Look up the current atmospheric CO2 concentration for the previous month?

https://www.co2.earth/

 

 

Methane’s Atmospheric Geologic History

Methane (CH4) is another effective greenhouse gas; in fact, it’s about 23 times more effective at trapping heat than CO2 is. Fortunately, it’s much less abundant in the atmosphere (measured in parts per billion instead of parts per million).

 

Unfortunately, atmospheric CH4 has increased by 250% since the late1700s (results from polar ice cores):

 

Methane forms when organic matter decays—which has been going on for billions of years. We need to understand why it has increased so much in the last few centuries.

 

Scientists estimate that 3/4 of all methane currently emitted into the atmosphere comes from human activities. Chief culprits are (1) decomposing landfills, (2) the processing of oil and gas, (3) “enteric fermentation, mainly cattle,” and (4) agricultural activities like growing rice.

 

11. The CH4 curve shows a dramatic upswing at 1800 A.D. Applying what you know about human history, discuss whether each of the four sources listed above is likely to have increased in the last 200 years. In other words, evaluate the proposal that the increase in CH4 is due to human activities. Identify specific trends, activities, etc. that support your ideas.

 

 

Click or tap here to enter text.

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