In this chapter we have constructed four distinct pledge cases that could result from different policy choices of Governments or from different outcomes of the negotiations. These four cases are combinations of the following two interdependent factors:
Unconditional versus conditional pledges: We have distinguished between countries’ unconditional and conditional pledges. Several industrialized countries have made pledges conditional on actions from other countries or the passing of domestic legislation, and developing countries’ pledges are often conditional on finance or technology transfer. We have made common assumptions as to whether a country’s pledge is deemed conditional or not (detailed in Appendix 2) and applied that to all modelling groups’ estimates. We have then summed the estimates to create a global total, which also includes international transport emissions. Note that where a country does not have an unconditional pledge (e.g. Canada, Japan, US and South Africa) the business-as-usual estimate for that country is assumed for the unconditional case reflected in Figure 241.
“Lenient” versus “strict” rules: We have adjusted these results to take into account the maximum42 impact of two unresolved issues in the negotiations: LULUCF accounting and the use of surplus emissions units. These issues have the potential to displace mitigation action in other sectors and thus lead to higher global emissions in 2020. The adjustments made are based on a review of existing literature and are reflected in the two “lenient” pledge cases (the “strict rules” cases do not include any impact from these issues). Specifically, for LULUCF accounting we have applied a maximum expected impact of 4.2 per cent of 1990 Annex I emissions annually in 2020 (approximately 0.8 GtCO2e). We assumed that credits of this magnitude would be given for carbon removals from existing forests or other sinks that would have occurred without further policy interventions (see Box 3b). For surplus emissions units, we have made two adjustments: the first for the expected impact of surplus emissions units “carried over” or “banked” from the first commitment period and used in the next. We have applied the maximum expected impact of 1.3 GtCO2e on 2020 emissions. The second adjustment is to account for any new surplus units that are expected to be generated in the next commitment period as a result of the pledges from Russia, Ukraine and Belarus remaining above business-as-usual. The expected impact of these depends on the modelling assumptions of each group and ranges up to 1 GtCO2e in 2020.43 A more detailed description of these issues and adjustments is available in Appendix 1.
In order to make consistent comparisons across modelling groups, we have had to adjust the global emission estimates of some groups to ensure that all sectors and countries are covered. In the case where data were missing (e.g. international transport emissions), we have added the median value of other modelling groups’ data. In addition, in order to ensure a consistent comparison with the results from Chapter 2 we have harmonised the data for the same 2005 emissions used in that chapter. These adjustments result in slightly different emission levels for each of the groups compared with those included in their publications. Appendix 3 provides more detail on the differences between modelling groups’ findings and the adjustments made.
In Figure 2 we show median results for each case to reflect the clustering of results from modelling groups. In the text we report the 20th and 80th percentile range to reflect the majority of the results.