Analysing the conflicting requirements of the Framework Convention on Climate Change

The objectives of the Framework Convention on Climate Change imply the conflicting constraints of minimising concentrations and maximising emissions (i.e. minimising emission restrictions). Carbon cycle models are readily used for ‘forward’ calculations of future CO₂ given specified emissions and the ‘inverse’ problem of deducing the emissions required to achieve specified concentration profiles. However these approaches (a) are each geared to only one side of the problem; and (b) each requires the specification of a particular pathway in terms of either emissions or concentrations. These limitations can be avoided by analysing the relations between future emissions and concentrations of CO₂ using a formalism that optimises over all possible future emission profiles, subject to relevant constraints on both emissions and concentrations. We present specific calculations indicating which combinations of upper bounds on concentrations and lower bounds on emissions are mutually inconsistent and which are consistent. We also calculate the (smaller) consistency regions that apply if emission reductions are restricted to less than 0.5% p.a. or less than 1% p.a. In each case, two reference periods (1990-2100 and 1990-2200) are considered.