Also in this chapter:
For this assessment, the analyses of 13 modelling groups have been reviewed39. Of these, nine groups have performed a global analysis and four have focused on either Annex I or a subset of other countries. These groups have made different assumptions about how the conditionality of pledges plays out in global emissions. Hence, adjustments have been made to the various estimates, in order to facilitate a meaningful comparison. The adjustments made are briefly explained in Box 3a and detailed in the appendices available online. The aim has been to construct a set of pledge cases with estimates of different 2020 emission levels.
To estimate emissions expected in 2020 we have to make assumptions about the policy choices of governments. Since these choices are uncertain we specify four different cases, each giving a different combination of choices (Box 3a). The results for emissions are as follows (and are summarised in Figure 2):
As a reference point, without pledges global greenhouse gas emissions may increase from 45 GtCO2e in 2005 to around 56 GtCO2e in 2020 (with a range44 of 54-60 GtCO2e) according to business-as-usual projections.
It is worth noting that there is the possibility of higher global emissions if international offsets are counted towards both industrialized and developing countries’ pledges (the so-called “double counting” of offsets). It should also be noted that in some countries the impact of existing domestic policies or national plans could lead to lower emissions than the conditional pledges submitted to the Copenhagen Accord. International climate finance could also leverage further mitigation and lower emissions. All these issues have been analysed and found to have a significant effect on 2020 emissions. However, they are not included in any of these cases but are discussed as additional factors in Section 3.4 below.
From the analysis of these four cases it is interesting to note that the international policy options being discussed in the UNFCCC negotiations, and inherent in these cases, can significantly reduce the level of emissions in 2020. The most ambitious of the cases (case 4) is expected to be 7 GtCO2e lower than business-as-usual emissions (range of 6-9 GtCO2e lower).
For Annex I countries, in the least ambitious case (“unconditional pledges, lenient rules”), emissions are estimated to be 6 per cent above 1990 levels (range of 1-12 per cent above) or equivalent to business-as-usual emissions in 2020. In fact, in many cases the use by Annex I countries of surplus units and “lenient LULUCF credits” provides more overall emission units than needed. This could result in higher emissions after 2020 if those units were to be banked for use in the following period.
In the most ambitious case (“conditional pledges, strict rules”), Annex I emissions in 2020 are expected to be 16 per cent below 1990 levels (range of 15-18 per cent below) and 20 per cent below business-as-usual emissions (range of 17-26 per cent).
For non-Annex I countries, in the least ambitious case (“unconditional pledges”) emissions are estimated to be 7 per cent lower than business-as-usual emissions (range of 6-8 per cent lower). In the most ambitious case (“conditional pledges”), non-Annex I emissions are 9 per cent lower than business-as-usual (range of 8-9 per cent lower).
This implies that the aggregate Annex I countries’ emission goals are less ambitious than the 25-40 per cent reduction by 2020 (compared with 1990) suggested in the IPCC Fourth Assessment Report (IPCC 2007a). Collectively the non-Annex I countries’ goals are less ambitious than the 15-30 per cent deviation from business-as-usual which is also commonly used as a benchmark (den Elzen and Höhne 2008, 2010). Whilst these values are helpful as a benchmark, it should be noted that, as described in chapters 2 and 4, various other emission pathways are consistent with the 2° C and 1.5° C temperature limits.
The cases presented in Figure 2 will be taken forward into the next chapter, which compares global emissions projections for 2020 with the emission pathways associated with limiting temperature rise to 2° C or 1.5° C. There are many possible combinations of the uncertainties considered in the preceding section that may lead to different 2020 emissions. However, the four cases presented above represent a reasonable summary of the potential low and high ambition outcomes that may be associated with the pledges.
Several options exist for policymakers to influence the final global 2020 emission level by delivering on their highest announced ambition and ensuring that accounting rules do not displace mitigation, and by finding ways to deliver further ambition either domestically, through finance or in sectors not currently covered.
All emissions in this figure and chapter refer to GtCO2e (gigatonnes or billion tonnes of carbon dioxide equivalent)—the global warming potential-weighted sum of the six Kyoto greenhouse gases, that is, CO2, CH4, N2O, HFCs, PFCs and SF6, including LULUCF CO2 emissions.
n = number of studies; High = maximum of full range; Low = minimum of full range; 20th-80th = 20th and 80th percentile values of the range
1. The data presented in the table have been harmonised to a common emissions level in 2005 (45 GtCO2e) in order to make these data more comparable to results in Chapter 2.
2. The range in 1990 emissions stems from the use of different data sources and assumptions especially for non-Annex I countries.
3. In the set of studies examined in this report, nine modelling groups have analysed the impact of pledges at the global level, while four have analysed only a subset of countries.