Most of the emission pathways consistent with a likely chance of meeting the 2º C limit show emissions peaking before 2020 (see Chapter 2). Hence, peaking is an important indicator of whether pledges are consistent with the 2º C limit.
Making an assessment of whether global emissions peak between now and 2020 requires understanding of where the emissions will be in 2020, as well as their trajectory in the interval between now and then. If the emissions in 2020 are close to or below current levels, then it is possible that emissions will peak over this period. Estimates of current (2009) emission levels are around 48 GtCO2e (Manning et al. 2010). Since only the most ambitious of the pledge cases comes close to current levels, we expect that this pledge case is the one most likely to result in a peak in emissions before 2020. By contrast, the least ambitious pledge case (“unconditional pledges, lenient rules”) results in a strong increase in emissions and is therefore the least likely to peak before 2020.
It should be noted that, it is also possible that emissions could peak before 2020, but still remain significantly above current levels in 2020. This could occur, for example, if the emission reduction policies are only introduced or start to take significant effect towards the end of this decade. However, it is difficult to assess the likelihood of this from the pledges alone.