Environmental science

Assignment #2 – Geosci 105 Online, Fall 2017

Atmospheric carbon dioxide record from Mauna Loa

(Due: Tuesday, Dec. 12, 2017 by 11:30 PM by D2L dropbox)

We have talked about the composition of the atmosphere in Chapter 14. We found out that though carbon dioxide is minor gas in Earth’s atmosphere, yet it is a critical one because it is a greenhouse gas. In Chapter 17 of the textbook, we will explore global change and the topic of greenhouse gases. So in this assignment, I thought we could investigate the carbon dioxide record at Mauna Loa in Hawaii. By plotting the actual data collected, I hope that we get a better feel for the problem of carbon dioxide concentrations in the atmosphere. The Mauna Loa Observatory is remote from industrial and other human-made sources of CO2. Downslope wind often transports CO2 from nearby volcanic vents. Even CO2 from vehicular traffic may disturb the measurements. The scientists at the Mauna Loa Observatory have tried to remove these types of local effects.

Methods

Air samples at Mauna Loa are collected continuously from air intakes at the top of four 7-m towers and one 27-m tower. Four air samples are collected each hour for the purpose of determining the CO2 concentration. Determinations of CO2 are made by using a Siemens Ultramat 3 nondispersive infrared gas analyzer with a water vapor freeze trap. This analyzer registers the concentration of CO2 in a stream of air flowing at ~0.5 L/min. Every 20 minutes, the flow is replaced by a stream of calibrating gas or “working reference gas”. In December 1983, CO2-in-N2 calibration gases were replaced with the currently used CO2-in-air calibration gases. These calibration gases and other reference gases are compared periodically to determine the instrument sensitivity and to check for possible contamination in the air-handling system. These reference gases are themselves calibrated against specific standard gases whose CO2 concentrations are determined manometrically. Greater details about the sampling methods at Mauna Loa are given in Keeling et al. (1982).

Hourly averages of atmospheric CO2 concentration, wind speed, and wind direction are plotted as a basis for selecting data for further processing. Data are selected for periods of steady hourly data to within ~0.5 parts per million by volume (ppmv); at least six consecutive hours of steady data are required to form a daily average.

Mauna Loa, Hawaii, U.S.A. Barren lava field of an active volcano 19°32′ N, 155°35′ W, 3397 m above MSL

Trends

The Mauna Loa atmospheric CO2 measurements constitute the longest continuous record of atmospheric CO2 concentrations available in the world. The Mauna Loa site is considered one of the most favorable locations for measuring undisturbed air because possible local influences of vegetation or human activities on atmospheric CO2 concentrations are minimal and any influences from volcanic vents may be excluded from the records. The methods and equipment used to obtain these measurements have remained essentially unchanged during the 43-year monitoring program.

Because of the favorable site location, continuous monitoring, and careful selection and scrutiny of the data, the Mauna Loa record is considered to be a precise record and a reliable indicator of the regional trend in the concentrations of atmospheric CO2 in the middle layers of the troposphere.

Year   Jan.    Feb.     March  April   May     June     July     Aug.     Sept.   Oct.      Nov.    Dec.   Annual Annual-Fit
1975 330.40 331.41 332.04 333.31 333.96 333.59 331.91 330.06 328.56 328.34 329.49 330.76 331.15    331.16
1976 331.74 332.56 333.50 334.58 334.87 334.34 333.05 330.94 329.30 328.94 330.31 331.68 332.15    332.18
1977 332.92 333.41 334.70 336.07 336.74 336.27 334.93 332.75 331.58 331.16 332.40 333.85 333.90    333.88
1978 334.97 335.39 336.64 337.76 338.01 337.89 336.54 334.68 332.76 332.54 333.92 334.95 335.50    335.52
1979 336.23 336.76 337.96 338.89 339.47 339.29 337.73 336.09 333.91 333.86 335.29 336.73 336.85    336.89
1980 338.01 338.36 340.08 340.77 341.46 341.17 339.56 337.60 335.88 336.02 337.10 338.21 338.69    338.67
1981 339.23 340.47 341.38 342.51 342.91 342.25 340.49 338.43 336.69 336.85 338.36 339.61 339.93    339.95
1982 340.75 341.61 342.70 343.57 344.13 343.35 342.06 339.82 337.97 337.86 339.26 340.49 341.13    341.09
1983 341.37 342.52 343.10 344.94 345.75 345.32 343.99 342.39 339.86 339.99 341.16 342.99 342.78    342.75
1984 343.70 344.50 345.29 347.08 347.43 346.79 345.40 343.28 341.07 341.35 342.98 344.22 344.42    344.44
1985 344.97 346.00 347.43 348.35 348.93 348.25 346.56 344.69 343.09 342.80 344.24 345.56 345.91    345.87
1986 346.29 346.96 347.86 349.55 350.21 349.54 347.94 345.91 344.86 344.17 345.66 346.90 347.15    347.14
1987 348.02 348.47 349.42 350.99 351.84 351.25 349.52 348.11 346.44 346.36 347.81 348.96 348.93    348.99
1988 350.43 351.72 352.22 353.59 354.22 353.79 352.39 350.44 348.72 348.88 350.07 351.34 351.48    351.44
1989 352.76 353.07 353.68 355.42 355.67 355.13 353.90 351.67 349.80 349.99 351.30 352.53 352.91    352.94
1990 353.66 354.70 355.39 356.20 357.16 356.22 354.82 352.91 350.96 351.18 352.83 354.21 354.19    354.19
1991 354.72 355.75 357.16 358.60 359.33 358.24 356.18 354.03 352.16 352.21 353.75 354.99 355.59    355.62
1992 355.98 356.72 357.81 359.15 359.66 359.25 357.03 355.00 353.01 353.31 354.16 355.40 356.37    356.36
1993 356.70 357.16 358.38 359.46 360.28 359.59 357.58 355.52 353.70 353.98 355.33 356.80 357.04    357.10
1994 358.36 358.91 359.97 361.27 361.68 360.94 359.55 357.49 355.84 355.99 357.58 359.04 358.89    358.86
1995 359.96 361.00 361.64 363.45 363.79 363.26 361.90 359.46 358.06 357.75 359.56 360.70 360.88    360.90
1996 362.05 363.25 364.02 364.72 365.41 364.97 363.65 361.49 359.46 359.60 360.76 362.33 362.64    362.58
1997 363.18 364.00 364.56 366.36 366.80 365.62 364.47 362.51 360.19 360.77 362.43 364.28 363.76    363.84
1998 365.32 366.15 367.31 368.61 369.30 368.87 367.64 365.77 363.90 364.23 365.46 366.97 366.63    366.58
1999 368.15 368.86 369.58 371.12 370.97 370.32 369.25 366.91 364.60 365.09 366.63 367.96 368.29    368.28
2000 369.08 369.40 370.45 371.59 371.75 371.62 370.04 368.04 366.53 366.63 368.20 369.43 369.40    369.40

Activity #1:

I have randomly selected six measurements collected at the Mauna Loa sampling site between 1986 and 1993 and highlighted the data in light blue. Plot the six points on the given graph below in blue ink or blue pencil. To hand in eventually you will need to scan the graph or use your phone to take a photo of the graph. Based on your data, is CO2 increasing or decreasing? Determine the rate of increase/decrease by calculating the slope of the line (remember back to high school science that slope=ΔY/ΔX or change in y-variable divided by change in x-variable) that best passes through your six data points.

Activity #2:

The CO2 concentration in the atmosphere is a concern because of it being an important greenhouse gas. High concentrations of carbon dioxide in the atmosphere contribute to global warming. How many years will it take for the CO2 concentration to double its 1993 content?

Activity #3:

I have highlighted six more measurements in red this time for the single year of 1988. Plot these six data points on your graph above. Does this change your interpretation? What new detail is added to the relationship when the more complete data is plotted? Why might CO2 vary throughout an individual year? Maybe think about photosynthesis by plants where CO2 and H2O are converted into sugars and oxygen.

Activity #4:

Below is some of the most recent CO2 data from Mauna Loa. Are CO2 levels higher or lower than those from the last part of the previous table? What is one aspect of global warming that concerns you most?

CO2 Trend for Mauna Loa

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