(1) If all the fluxes into and out of the atmosphere remain constant, how long would it take for the amount of carbon in the atmosphere to reach double the pre-industrial level (which was 590Gt(C))? ?years.
(2) If all the fluxes into and out of the Atmosphere remain constant except that fossil fuel emissions doubled to 12Gt(C)/yr (which is one projected emission scenario for 2040), how long would it take for the amount of carbon in the atmosphere to go from 760 to double pre-industrial at that rate of anthropogenic emissions? ?years.