National ‘fair shares’ in reducing greenhouse gas emissions within the principled framework of international environmental law

This article tests fairness justifications offered in 168 nationally determined contributions (NDCs) to the 2015 Paris Agreement against the touchstone of principles of international environmental law. It finds that while many NDCs refer to elements and indicators that are backed by principles of international law in determining fair shares (sustainable development, special circumstances, common but differentiated responsibilities and equity), some NDCs justify their contributions on the basis of indicators not backed by such principles (indicators including small share of global emissions (for states that are not LDCs and SIDSs), least cost pathways, and emissions per GDP). These insights are used to select a sub-set of approaches to the quantification of national fair share emissions targets among approaches previously surveyed in the literature. This leads to the exclusion of approaches based on cost and grandfathering. Next, the principles of harm prevention and precaution, and the normative pillars of the climate change regime, including its objective, ‘progression’, and ‘highest possible ambition,’ and the norms relating to human rights, are engaged to argue for further narrowing the range of national fair shares such that the sum of individual contributions is collectively compatible with the Paris Agreement’s long-term temperature goal. This leads to the finding that developed states have a Paris temperature goal compatible emission level in 2030 that is net-negative. Of the G20 states, only India and Indonesia can temporarily increase their emissions relative to 2010, only India relative to today. Around half the G20 states have increased emissions over the 2010s, and those decreasing emissions have done so too slowly. Key policy insights States’ fairness justifications for their contributions to the Paris Agreement should be scrutinized for compatibility with widely-accepted principles of international environmental law as well as the normative pillars of the climate change regime.Fair share ranges consistent with international environmental law principles offer a benchmark for existing and new nationally determined contributions under the Paris Agreement, for peer-to-peer comparisons, and to feed into the global stocktakes.Such fair share ranges can inform climate litigation in which the adequacy of national contributions, and thus a state’s fair share, is at issue. States’ fairness justifications for their contributions to the Paris Agreement should be scrutinized for compatibility with widely-accepted principles of international environmental law as well as the normative pillars of the climate change regime. Fair share ranges consistent with international environmental law principles offer a benchmark for existing and new nationally determined contributions under the Paris Agreement, for peer-to-peer comparisons, and to feed into the global stocktakes. Such fair share ranges can inform climate litigation in which the adequacy of national contributions, and thus a state’s fair share, is at issue

National ‘fair shares’ in reducing greenhouse gas emissions within the principled framework of international environmental law

This article tests fairness justifications offered in 168 nationally determined contributions (NDCs) to the 2015 Paris Agreement against the touchstone of principles of international environmental law. It finds that while many NDCs refer to elements and indicators that are backed by principles of international law in determining fair shares (sustainable development, special circumstances, common but differentiated responsibilities and equity), some NDCs justify their contributions on the basis of indicators not backed by such principles (indicators including small share of global emissions (for states that are not LDCs and SIDSs), least cost pathways, and emissions per GDP). These insights are used to select a sub-set of approaches to the quantification of national fair share emissions targets among approaches previously surveyed in the literature. This leads to the exclusion of approaches based on cost and grandfathering. Next, the principles of harm prevention and precaution, and the normative pillars of the climate change regime, including its objective, ‘progression’, and ‘highest possible ambition,’ and the norms relating to human rights, are engaged to argue for further narrowing the range of national fair shares such that the sum of individual contributions is collectively compatible with the Paris Agreement’s long-term temperature goal. This leads to the finding that developed states have a Paris temperature goal compatible emission level in 2030 that is net-negative. Of the G20 states, only India and Indonesia can temporarily increase their emissions relative to 2010, only India relative to today. Around half the G20 states have increased emissions over the 2010s, and those decreasing emissions have done so too slowly. Key policy insightsStates’ fairness justifications for their contributions to the Paris Agreement should be scrutinized for compatibility with widely-accepted principles of international environmental law as well as the normative pillars of the climate change regime. Fair share ranges consistent with international environmental law principles offer a benchmark for existing and new nationally determined contributions under the Paris Agreement, for peer-to-peer comparisons, and to feed into the global stocktakes. Such fair share ranges can inform climate litigation in which the adequacy of national contributions, and thus a state’s fair share, is at issue

Fairness and feasibility in deep mitigation pathways with novel carbon dioxide removal considering institutional capacity to mitigate

Questions around the technical and political feasibility of deep mitigation scenarios assessed by the Intergovernmental Panel on Climate Change have increasingly been raised as have calls for more directly analyzing and incorporating aspects of justice and fairness. Simultaneously, models are increasing the technical representation of novel carbon-dioxide removal (CDR) approaches to provide policy-relevant analyses of mitigation portfolios in the context of the rising number of net-zero CO _2 and GHG targets made by parties to the Paris Agreement. Still, in most cost-effective mitigation scenarios developed by integrated assessment models, a significant portion of mitigation is assumed to take place in developing regions. We address these intersecting questions through analyzing scenarios that include direct air capture of CO _2 with storage (DACCS), a novel CDR technology that is not dependent on land potential and can be deployed widely, as well as regional variations in institutional capacity for mitigation based on country-level governance indicators. We find that including novel CDR and representations of institutional capacity can enhance both the feasibility and fairness of 2 °C and 1.5 °C high-overshoot scenarios, especially in the near term, with institutional capacity playing a stronger role than the presence of additional carbon removal methods. However, our results indicate that new CDR methods being studied by models are not likely to change regional mitigation outcomes of scenarios which achieve the 1.5 °C goal of the Paris Agreement. Thus, while engineered carbon removals like DACCS may play a significant role by midcentury, gross emissions reductions in mitigation pathways arriving at net-zero CO _2 emissions in line with 1.5 °C do not substantially change. Our results highlight that further investment and development of novel CDR is critical for post-net-zero CO _2 mitigation, but that equitable achievement of this milestone will need to arrive through technical and financial transfers, rather than by substantial carbon removals in developed countries before mid-century

Are equilibrium multichannel networks predictable? The case of the regulated Indus River, Pakistan

Arguably, the current planform behaviour of the Indus River is broadly predictable. Between Chashma and Taunsa, Pakistan, the Indus is a 264-km-long multiple-channel reach. Remote sensing imagery, encompassing major floods in 2007 and 2010, shows that the Indus has a minimum of two and a maximum of nine channels, with on average four active channels during the dry season and five during the annual monsoon. Thus, the network structure, if not detailed planform, remains stable even for the record 2010 flood (27,100 m3 s− 1; recurrence interval > 100 years). Bankline recession is negligible for discharges less than a peak annual discharge of 6000 m3 s− 1 (~ 80% of mean annual flood). The Maximum Flow Efficiency (MFE) principle demonstrates that the channel network is insensitive to the monsoon floods, which typically peak at 13,200 m3 s− 1. Rather, the network is in near-equilibrium with the mean annual flood (7530 m3 s− 1). The MFE principle indicates that stable networks have three to four channels, thus the observed stability in the number of active channels accords with the presence of a near-equilibrium reach-scale channel network. Insensitivity to the annual hydrological cycle demonstrates that the timescale for network adjustment is much longer than the timescale of the monsoon hydrograph, with the annual excess water being stored on floodplains rather than being conveyed in an enlarged channel network. The analysis explains the lack of significant channel adjustment following the largest flood in 40 years and the extensive Indus flooding experienced on an annual basis, with its substantial impacts on the populace and agricultural production