1.2.3.6 Public good

The climate system tends to be overused (excessive GHG concentrations) because of its natural availability as a resource whose access is open to all free of charge. In contrast, climate protection tends to be underprovided. In general, the benefits of avoided climate change are spatially indivisible, freely available to all (non-excludability), irrespective of whether one is contributing to the regime costs or not. As regime benefits by one individual (nation) do not diminish their availability to others (non-rivalry), it is difficult to enforce binding commitments on the use of the climate system^[4] (Kaul et al., 1999; 2003). This may result in ‘free riding’, a situation in which mitigation costs are borne by some individuals (nations) while others (the ‘free riders’) succeed in evading them but still enjoy the benefits of the mitigation commitments of the former.

The incentive to evade mitigation costs increases with the degree of substitutability among individual mitigation efforts (mitigation is largely additive) and with the inequality of the distribution of net benefits among regime participants. However, individual mitigation costs decrease with efficient mitigation actions undertaken by others. Because mitigation efforts are additive, the larger the number of participants, the smaller the individual cost of providing the public good – in this case, climate system stabilization. Cooperation requires the sharing of both information on climate change and technologies through technology transfers as well as the coordination of national actions lest the efforts required by the climate regime be underprovided.

1.3.3.7 Equity

Equity is an ethical construct that demands the articulation and implementation of choices with respect to the distribution of rights to benefits and the responsibilities for bearing the costs resulting from particular circumstances – for example, climate change – within and among communities, including future generations. Climate change is subject to a very asymmetric distribution of present emissions and future impacts and vulnerabilities. Equity can be elaborated in terms of distributing the costs of mitigation or adaptation, distributing future emission rights and ensuring institutional and procedural fairness (Chapter 13, Section 13.3.4.3). Equity also exhibits preventative (avoidance of damage inflicted on others), retributive (sanctions), and corrective elements (e.g. ‘common but differentiated responsibilities’) (Chapter 2, Section 2.6), each of which has an important place in the international response to the climate change problem (Chapter 13).