Answer THREE questions, at least ONE question from EACH section.

Transcription

1 UNIVERSITY OF EAST ANGLIA School of Environmental Sciences Main Series Postgraduate Examination THE CARBON CYCLE AND CLIMATE CHANGE ENV-MA31 Time allowed: 2 hours. Answer THREE questions, at least ONE question from EACH section. Answer EACH question in a SEPARATE answer book. All questions have equal weighting. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. ENV-MA31 Module Contact: Dr A Manning, ENV Copyright of the University of East Anglia Version 1

2 2 SECTION A 1. a) Explain what is meant by a positive feedback, and a negative feedback, in the context of greenhouse gases and the Earth s climate system. [15%] b) Give examples of two physical climate feedbacks, and outline the processes involved. [20%] c) Give examples of three carbon cycle-climate feedbacks, and outline the processes involved. You should explain whether these are positive or negative feedbacks, and why. [45%] d) Explain the difference between coupled and uncoupled carbon-climate models. Briefly describe how the C4MIP carbon-climate models were used to quantify carbon-climate feedbacks. [20%] 2. You are asked to brief Owen Paterson, the UK Secretary of State for Environment, Food and Rural Affairs on ocean acidification. Using diagrams and relevant references, explain: a) what is ocean acidification? [15%] b) the ocean measurements which show that this is happening now. [15%] c) data that suggest that the growth of coccolithophores has been linked to atmospheric CO 2 concentrations over the past 200,000 years. [20%] d) the advantages and disadvantages of laboratory scale and mesocosm approaches to studying the impact of ocean acidification on planktonic ecosystems. [25%] e) experiments which show the summative effect of ocean acidification and increasing temperatures on phytoplankton photosynthesis and calcification. [25%] 3. a) Atmospheric CO 2 concentration during the last glacial maximum (LGM) was significantly different from the pre-industrial value. List the approximate values of background CO 2 concentration, in ppm, at the LGM, pre-industrial world, and today. [10%] b) Briefly, how do the atmospheric CO 2 concentrations given in part a) compare to those from more than 100 million years ago. [10%] c) With the aid of diagrams, describe the three different Milankovitch cycles. [30%]

3 3 d) Several processes are thought to have contributed to the LGM atmospheric CO 2 concentration being different from the pre-industrial value. Describe three such processes. Include in your description the approximate size and direction of the contribution of each process to the glacial interglacial CO 2 difference, and the type of proxy data used to determine the information. [50%] SECTION B 4. a) Discuss the main lines of evidence from atmospheric measurements that demonstrate the fact that rising CO 2 concentrations in the atmosphere are a result of fossil fuel combustion, and are not due to natural sources. [60%] b) The bottom panel of the figure below shows δ 13 C measurements of CO 2 (in ) made at Barrow, Alaska (71ºN), with data from 1990 to Describe the main processes which result in the seasonal cycle and long-term trend shown. The top panel shows concurrent measurements of CO 2 concentration (in ppm); you should not explain the top panel, but it may assist you in answering the question. [40%] PLEASE TURN OVER

4 4 5. a) Describe the rectifier effect as applied to atmospheric measurements. Discuss how atmospheric transport models that do not account for the rectifier effect will give erroneous results when computing CO 2 concentrations at ground-level observation sites. [40%] b) The two figures below show two 1-week periods of continuous atmospheric measurements collected from UEA s Weybourne Atmospheric Observatory. The left figure shows data from 29 July 2012 to 05 August 2012; the right figure shows data from November The top panels show CO 2 concentration, the middle show O 2, and the bottom show APO, that is, Atmospheric Potential Oxygen. Y-axis ranges shown are the same for both figures, namely: CO 2 : 360 to 460 ppm; O 2 : -900 to -300 per meg; APO: -450 to 0 per meg. Describe in detail the most prominent features or events illustrated in these figures and discuss the possible causes of these features. [60%] 6. a) For the terrestrial biosphere, briefly define the terms GPP (Gross Primary Production), NPP (Net Primary Production), NEP (Net Ecosystem Production) and NBP (Net Biosphere Production). [20%] b) In a particular forest, GPP is determined to be 10 Gg C/yr. The net amount of O 2 released by this forest is 2 Gg O 2 /yr. Calculate the NBP of this forest in Gg C/yr. Assume all photosynthesis, respiration and terrestrial combustion processes consume and produce atmospheric CO 2 or O 2 at a molar ratio of 1.1 mol O 2 per mole of CO 2. Also note that 1 Gg = 10 9 g. [15%] c) Given that there are no disturbances in this forest, and that all non-plant respiration processes produced CO 2 equivalent to 5 Gg C/yr, how much O 2 must have been consumed by plant respiration, in Gg O 2 /yr? [30%] d) What are the values for NPP and NEP for this forest, in Gg C/yr? Which of all of these productivity terms (GPP, NPP, NEP, NBP) is most relevant to the net land biospheric carbon sink? [15%]

5 5 e) In 2010, global CO 2 emissions from fossil fuel combustion were 9.1 Pg C. How much atmospheric O 2 must have been consumed in these combustion processes? Assume that the global average O 2 :CO 2 molar ratio for fossil fuel combustion is 1.40:1.00. Express your answer in Pg O 2. (1 Pg = g). [10%] f) Given that the total moles of dry air in the global atmosphere is 1.769x10 20, calculate the global decrease in atmospheric O 2 concentration, in ppm, caused by the fossil fuel combustion in 2010 that you calculated in e). Assume no other processes affect atmospheric O 2 concentration. [10%] END OF PAPER