(Roque Pedace) The climate system is a (global) ‘commons’ with different environmental roles. Up to the industrialization era it was considered a public good , since in practice it was infinite (it didn’t wear out with use) and non exclusive (use does not prevent others from using it). As greenhouse gases (GHG) have accumulated, the latter property was lost, since the current and future users no longer enjoy the possibility of emitting these gases without restrictions, since we are running the risk of a climate catastrophe for all. The system can now be compared to a road or a bridge, that wear out insignificantly when used, but which have a limited transportation capacity (in this case, the capacity of the atmosphere to absorb and recycle emissions in a stable way). Consequently, past and present emitters that exceed their quota (be it States, companies or individuals) have appropriated themselves of the system at the expense of others. In other terms, they occupy the environmental space of others. This happens as a result of obtaining de facto property rights, since the emitters are not the owners of the system in the same way that someone owns water or forests once he or she has obtained that right through the processes of privatization of goods and services. In fact, they do not appropriate themselves of the air as such, but of the right to contaminate it without taking responsibility for their polluting action.
The overall quantity of emissions that should be eliminated to recover the environmental integrity of the climate system is regardless of these considerations. But the future distribution of these reductions (mitigation) is not. The past emissions have an accumulative effect in the atmosphere and make up a climate debt that should be paid to those who were and are being de facto expropriated of their environmental space.
Meanwhile, to estimate the amount of that debt, the environmental space should be accurately defined, so many proposals have considered that we are all equal in the eyes of the atmosphere and therefore everyone has the same right of use (per capita equality principle). The Kyoto Protocol has not adopted this principle, but the one of ‘grandfathering’ (or acquired rights), by which those who polluted the most, could continue doing so as long as they accepted progressive reductions, whilst those who polluted the least, did not have reduction obligations. Currently, despite the mandatory reductions assigned to them by the Protocol, the former (be it States, companies or individuals) continue obtaining most of the benefits from the exploitation of fossil fuels and continue transferring proportionally their environmental impacts caused by climate change to the entire human kind, at negligible costs .
This unlawful appropriation of the atmosphere is at the root of the conflict, regardless in which way the reductions that were agreed under the Protocol are implemented. In fact, it would still be an unfair distribution, even if there were no market mechanisms involved and if the reductions were only applied at source, where the emissions originated. Thus, there is no cause-effect relation between both. Nonetheless, it can be rightfully argued that the Clean Development Mechanism (CDM), one of the Kyoto Protocol’s market mechanisms, is unfair from the outset, since the largest polluters are trading emission rights to which they are not legitimately entitled (regardless of other CDM injustices, such as the commodification of forests, the increase in the climate debt, etc.).
The solution agreed in the Protocol was actually the acceptance of a de facto situation, that is, that those that are historically responsible (for climate change) were not willing to apply justice criteria to burden sharing. Besides rejecting the assignment of per capita rights –which result from considering the atmosphere as a (global) commons—other criteria, such as the differentiated ability of the parties to act, were not duly taken into account, for instance, owing to the unequal wealth of the nations (also to some extent linked with the unequal current and past usage of the climate system).
The United Nations Framework Convention on Climate Change (UNFCCC), in contrast, includes principles such as the differentiated historical responsibility, which can be advocated as the basis for a solution based on justice.Also, the shared management approach (ideally exercising solidarity) of (global) commons such as the atmosphere is accepted in the UN ,as opposed to grandfathering the access to the resources in it .
Demand for climate justice has been targeted primarily against this appropriation of the quota of space in the climate system, which the governments who bear the greatest share of responsibility have attributed to themselves based on (ad hoc) power relations, instead of on explicit criteria of equity. It has also focused on urging them to take responsibility for the damages caused by their impacts, i.e. the reparation and compensation costs, besides the costs of the urgently needed energy transition (ie adaptation and mitigation costs).
It should also be taken into account that if the historical responsibility promoted by the Convention is taken seriously (see various documents on climate debt, eg Bolivian submission) , some countries should have inmissions, that is, negative emissions. One way to accomplish this is through domestic biological carbon sinks , but these are plagued with a variety of problems, both political and practical., eg the commodification of nature through plantations projects as proposed in the CDM or now in REDD. A better approach entails emissions reductions abroad which they should somehow pay for. This means an obligation to pay for sustainable activities without fossil fuels in the countries with the least share of responsibility. This is a big challenge for developing countries since they must adopt a zero emission target and at the same time fight for the recognition of this debt.
 The countries where the CDM projects are implemented get very little income out of that, and they sell their cheapest reduction options, which have little effect for a long term clean development and a more doubtful contribution to sustainability.