We know of no other recent modeling exercise that exhibits all these useful features. Nevertheless, we also recognize some important limitations of the EMF22 study. These include, for instance, the question of how aerosols and land use impacts are represented in the models. We note in the subsequent sections where these limitations affect our analysis, but overall we do not believe these effects significantly change our main conclusions and recommendations.
167 gigatons (Gt) CO2-eq9 (and a 50 percent reduction corresponds to a budget of 203 Gt CO2-eq10). Table 2.1 illustrates that the budget values do not change a great deal if different baseline years are selected. This is a useful characteristic of a cumulative budget, since the choice of baseline year is often an issue of contentious debate in policy negotiations.
We chose to round these EMF numbers and adopt a cumulative emissions budget in a range of 170 to 200 Gt CO2-eq over the period 2012-2050 as a reasonably representative U.S. budget target, which can serve as a benchmark for developing policy recommendations and testing their feasibility. This budget range, which represents a significant change from business-as-usual U.S. emissions out to 2050, is roughly in line with the types of emissions-reduction goals found in many recent policy propos-