  Probabilistic projections of baseline (with no additional mitigation
policies) future carbon emissions are important for sound climate risk
assessments. Deep uncertainty surrounds many drivers of projected emissions.
Here we use a simple integrated assessment model, calibrated to century-scale
data and expert assessments of baseline emissions, global economic growth, and
population growth, to make probabilistic projections of carbon emissions
through 2100. Under a variety of assumptions about fossil fuel resource levels
and decarbonization rates, our projections largely agree with several emissions
projections under current policy conditions. Our global sensitivity analysis
identifies several key economic drivers of uncertainty in future emissions and
shows important higher-level interactions between economic and technological
parameters, while population uncertainties are less important. Our analysis
also projects relatively low global economic growth rates over the remainder of
the century. This illustrates the importance of additional research into
economic growth dynamics for climate risk assessment, especially if pledged and
future climate mitigation policies are weakened or have delayed
implementations. These results showcase the power of using a simple,
transparent, and calibrated model. While the simple model structure has several
advantages, it also creates caveats for our results which are related to
important areas for further research.
