Carbon cycle variations over time

We have emphasized in Section 8.09.3 that the carbon-cycle variations observed on glacial/ interglacial time scales during the Quaternary period can be understood in terms of the redistribution of carbon among the atmosphere, oceans, biosphere, and reactive sediments. Over timescales of millions of years and longer, many... 

Secular variation Offsets or deviations from equilibrium natural C concentrations due to production rate variations and/or changes in the parameters of the carbon cycle over time. 

One of the most fundamental assumptions of the method is the requircment that natural C concentrations in materials of zero " C age in a particular carbon reservoir are equivalent to that which has been characteristic of living oi nisms in that same reservoir over the entire time scale. Generally this assumption is seen to require an eqnilibrinm or steady-state relationship in which the prodnction and decay rates have been in approximate balance. Since the decay rate of " C is constant, the principal variables affecting equilibrium conditions would be changes in the atmospheric prodnction rate of " C, long-and short-term climatic perturbations arrd effects related to variations in the parameters of the carbon cycle such as reservoir sizes and rates of trarrsfer of between differ-... 

---