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Carbon Cycle

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Animation Assessment

Question 1 of 5

On an annual basis, what is the net result of the contributions/removals of CO₂ from the atmosphere due to global photosynthesis and respiration (both terrestrial and marine)?

Question 1 choicesChoice A., approximately 3 gT yr^-1 decreaseChoice B., approximately 9.5 gT yr^-1 increaseChoice C., approximately 209 gT yr^-1 increaseChoice D., approximately 212 gT yr^-1 decrease

Correct.

Incorrect.

Question 2 of 5

Measurable increases in carbon dioxide in the atmosphere over the past 200 years have resulted primarily from human addition of carbon dioxide from:

Question 2 choicesChoice A., burning fossil fuels for heating, cooling and transportation.Choice B., clear cutting forests.Choice C., Both of these choices are correct.

Correct.

Incorrect.

Question 3 of 5

Net human inputs to atmospheric carbon dioxide per year are estimated at approximately 8.8 gigatons. This is considerably less than the 209 gigatons of carbon dioxide added to the atmosphere by the respiration of all marine and terrestrial organisms. Given this, should we be concerned?

Question 3 choicesChoice A., We shouldn’t be concerned; this addition is much too small to make a difference.Choice B., We shouldn’t be concerned; variations in CO₂ levels are naturally occurring events.Choice C., We should be concerned because this addition is not counterbalanced by photosynthesis or other removal processes and therefore can accumulate or build in the atmosphere over many years leading to climate change.Choice D., We should be concerned because this addition is not counterbalanced by respiration or other removal processes and therefore can accumulate or build in the atmosphere over many years leading to climate change.

Correct.

Incorrect.

Question 4 of 5

Estimates are that all natural processes (not including human activities) result in a near balance between carbon entering and leaving the atmosphere (actually slightly less entering than leaving). What is the estimate of the excess CO₂ in gigatons of carbon per year added to the atmosphere from human activities (that is, the amount above that removed by natural processes)? (Select the closest value.)

Question 4 choicesChoice A., 9.5 gigatons yr^-1Choice B., 8.0 gigatons yr^-1Choice C., 5.2 gigatons yr^-1Choice D., 218.6 gigatons yr^-1Choice E., 213.4 gigatons yr^-1

Correct.

Incorrect.

Question 5 of 5

Reforestation efforts around the world contribute to increased uptake of CO₂ from the atmosphere and conversion to organic matter. Deforestation, on the other hand, typically by clearing and burning of natural vegetation, results in added CO₂ in the atmosphere. What is the current estimate of the annual net balance between these two processes?

Question 5 choicesChoice A., atmospheric increase by 0.5 gT yr^-1Choice B., atmospheric increase by 1.0 gT yr^-1Choice C., atmospheric decrease by 1.0 gT yr^-1Choice D., atmospheric increase by 1.5 gT yr^-1Choice E., atmospheric decrease by 1.5 gT yr^-1

Correct.

Incorrect.

Assessment Summary

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