Reservoirs in Non-steady-state

Let us analyze the situation when one observes a change in reservoir content and wants to draw conclusions regarding the sources and sinks. We 

Tobs fo- In this case, there has to be an approximate balance between the two terms on the right-hand side of the equation  

This means that the observed change in M mainly reflects a change in the source flux Q or the sink function. As an example, we may take the methane concentration in the atmosphere, which is now increasing by about 1% per year. The turnover time is estimated to be about 10 years, i.e. much less than r bs of 100 years (Cicerone and Oremland, 1988). Consequently, the observed rate of increase in atmospheric methane is a direct consequence of a similar rate of increase of emissions into the atmosphere. (In fact, this is not quite true. A fraction of the observed increase is probably due to a decrease in sink strength caused by a decrease in the concentration of hydroxyl radicals responsible for the decomposition of methane in the atmosphere.) 

2- fobs fo- lo this case, the balance is dM/dt = Q, which means that there is an increase in reservoir content about equal to the source flux with little influence of the sink. The reservoir is then in an accumulative stage and its mass is increasing with time largely as a function of Q. The content of CFC-12 in the atmosphere is an interesting example of this situation. The observed increase is about 4% per year (ToSs 25 years) and the turnover time is about 120years. The rate of increase is thus a reflection of an imbalance between sources and sinks rather than an increase in the source flux Q. The emissions of CFC-12 actually remained essentially constant between 1974 and 1988. 

In situations where T bs is comparable in magnitude to To, a more complex relation prevails between Q, S, and M. Atmospheric CO2 falls in 

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