LIFSCI 7B XL - Animation: Carbon cycle

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.)

5.2 gigatons yr-1

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)?

Approximately 3 gT yr^(-1) decrease

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?

Atmospheric increase by 1.0 gT yr-1

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

Both of these choices are correct: -Burning fossil fuels for heating, cooling and transportation. -Clear cutting forests.

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?

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.