The time path of emissions also varies across models for a variety of reasons, including (1) differences in reference scenario emissions, (2) differences in the cost of abatement over time, (3) differences in the speed at which capital stock can be replaced, and (4) differences in assumptions about foresight (Fawcett et al. 2009). (link.springer.com)
In practice the growth in emissions is likely to be considerably less than this, because the IEA Reference Scenario does not take account of new policies that are under consideration in many countries. (johnquiggin.com)
Differences in carbon prices can be attributed to differences in reference scenario emissions, and thus the level of abatement required, along with differences in the cost of abatement technologies. (link.springer.com)