Reducing uncertainty in projections of terrestrial carbon uptake

Here, we quantify and isolate the sources of projection uncertainty in cumulative ocean and terrestrial carbon uptake over 2006-2100 by performing an analysis of variance on output from an ensemble of 12 Earth System Models.

Whereas uncertainty in projections of global ocean carbon accumulation by 2100 is 160 Pg C and driven primarily by model structure. To statistically reduce uncertainty in terrestrial carbon projections, we devise schemes to weight the models based on their ability to represent the observed change in carbon accumulation over 1959-2005. The weighting schemes incrementally reduce uncertainty to a minimum value of 125 Pg C in 2100, but this reduction requires an impractical observational constraint.