(4a) The pre-industrial atmosphere (around 1750) had a CO2 concentration of about 280 ppm. Using the conversion factor from lecture (2.124 GtC per 1 ppm), what is the corresponding mass of the pre-industrial atmospheric carbon pool in GtC? Round your answer to zero decimal places.
(4b) [1 point] The atmospheric CO2 concentration is currently around 415 ppm. What is the corresponding mass of the current atmospheric carbon pool in GtC? Round your answer to zero decimal places.
(4c) [1 point] How much carbon (in GtC) have human activities added to the atmosphere between 1750 and now? Round your answer to zero decimal places.
