In the absence of abatement policies global greenhouse gas (GHG) emissions

are estimated to grow at an annual rate of 5%. Suppose the current level of

emissions is 7.5 GtC. The current stock of CO2 is estimated to be 800 GtC.

The pre-industrial level of stock is 590 GtC. Suppose a decay rate of 0.01

applies.

a. Calculate the time when emissions will have doubled?

b. Does the stock grow or decline currently? By how much?

c. Does the stock grow or decline in one year from now? By how much?

d. Is the change in stock slowing down or accelerating?

Now suppose freezing of global emissions is negotiated and implemented,

that is, emissions are constant at their current level.

e. At which level will the stock of CO2 be stationary (i.e. it will not change

anymore)?

f. Which level of emissions can be allowed if global CO2 stocks should not

exceed the double pre-industrial level?