○ Violations of academic integrity can include both academic and legal
consequences. It is your responsibility to be aware of the University’s policies
and procedures; claiming ignorance will not excuse you from this responsibility,
nor the consequences of your actions.
○ You must include your declaration of independent work when submitting each
part of the examination – please see below. Submissions that do not include this
declaration will not be accepted for assessment.
● This is an open-book examination. You may make use of resources available to you
both on and off line, as long as they do not involve the need to interact with others.
● Use of calculators is permitted as needed.
● To assist in translation between English and a student’s native language, a dictionary
may be used.
● During the examination, you may only ask questions of the instructor and/or teaching
assistants via eClass; you should not interact with your peers in the class through these
forums. Only private and confidential matters should be communicated via email to the
instructor.
DECLARATION
You must include the following declaration in each part of your exam submission. Failure to
comply with this requirement will result in your submission not being accepted for assessment.
The declaration to include must read as follows:
I, [insert legal name and York University student number], declare that I have worked
independently to complete Part B of the F21 NATS 1780 A final examination. All work
submitted is my own, unless otherwise attributed.
Answer all questions. This question is worth 35 marks. To receive full marks, you must show all
work used to arrive at final answers; part marks will be awarded on the basis of work shown.
Note that this includes all figures, sketches, etc.
1. Suppose you are designing a satellite-based instrument to remotely sense the presence
or absence of methane in Earth’s atmosphere via its absorption spectrum.
a. If methane was the only gas present in Earth’s atmosphere, for which
wavelengths would you need to calibrate your instrument to detect the presence
or absence of methane? [1 mark]
b. Earth’s atmosphere includes gasses other than methane.
i. Which of these gasses ‘interferes’ with your instrument’s ability to detect
the presence or absence of methane? Why is this the case? [2 marks]
ii. How might you be able to design your instrument to exclude the impact of
these other gasses, and thus focus on methane in isolation? [2 marks]
2. Trends in atmospheric methane data are available here. Using the data that focuses on
just the past five years, and for a specific month during the May 2018 and March 2019
timeframe:
a. Estimate the methane concentration in ppb from the black curve. [1 mark]
b. Estimate the methane concentration in ppb from the red curve. [1 mark]
c. Estimate the seasonal variation in the methane concentration by calculating the
difference between your estimates in questions 4(a) and 4(b). [1 mark]
d. What is the most-likely source of seasonal variations in methane concentration?
[1 mark]
3. Assume your instrument is able to detect the presence or absence of methane – in other
words, you have been able to exclude the impact of other gasses, and thus focus on
methane in isolation. Instruments such as yours need to be calibrated (or ‘tuned’) in
order to report the amount of methane detected.
a. How might you make use of the Question 2 data to calibrate your instrument to
report the absolute concentration of methane? (Hint: How might you establish the
quantitative connection between methane absorption and methane
concentration?) [2 marks]
b. How might seasonal methane trends (e.g., Question 2(b)) complicate your
calibration process? [1 mark]
c. By making use of methane measurements over the past 38 years, describe the
overall trend. [1 mark]
d. How might long-term methane trends (Question 3(b)) complicate your calibration
process? [1 mark]
4. In reference to Figure 1 from the Zhang et al. research article here:
a. Specifically, what is the data (including units) quantified through use of the colour
scale? [1 mark]
b. For the state of California:
i. Estimate the peak value by making use of the colour scale. [1 mark]
ii. Estimate the peak ‘methane anomaly’ by subtracting your Question 2(a)
estimate from your estimate for Question 4(b)(i). [1 mark]
iii. According to the research paper: “… notable enhancements are observed
in California’s central valley … likely associated with anthropogenic
(agriculture, dairy) and natural (wetland) sources.” Create a process-flow
diagram that accounts for each of these two methane sources. [4 marks]
c. For the Permian Basin:
i. Estimate the peak value by making use of the colour scale. [1 mark]
ii. Estimate the peak ‘methane anomaly’ by subtracting your Question 2(a)
estimate from your estimate for Question 4(c)(i). [1 mark]
iii. Through venting and leaks, methane is released as a consequence of oil
production. Add these sources to your Question 4(b)(iii) process-flow
diagram. [2 marks]
iv. Flaring refers to the combustion (i.e., burning) of methane – a chemical
process in which methane reacts with molecular Oxygen to produce
Carbon Dioxide and water vapour. Account for flaring in your Question
4(b)(iii) process-flow diagram. [2 marks]
d. How do the methane anomalies estimated in questions 4(b)(ii) and 4(c)(ii)
compare or contrast? [1 mark]
5. Consider the global methane budget, and specifically top-down figures for the 10-year
period 2008-2017 here.
a. Provide a rough estimate for “agriculture and waste” contributions relative to
“fossil fuel production and use”. [1 mark]
b. Compare and contrast your answers from questions 5(a) with 4(d)? How might
you account for any similarities or differences? [2 marks]
6. Regarding the present day.
a. Estimate current levels of methane concentration in ppb from the black curve
here. [1 mark]
b. Determine the increase relative to present by subtracting your Question 2(a)
estimate from your estimate obtained in Question 6(a). [1 mark]
c. Assuming the increase implied by Question 6(b) applies directly, provide
estimates of the current values for the peak methane anomalies in the state of
California. [1 mark]
d. Zhang et al. identified both natural and anthropogenic sources as contributors to
methane emissions in the state of California. How might the relative increase in
methane concentrations implied by Question 6(c) be reconciled with these
sources? [1 mark]