Informant38

Origins and estimates of uncertainty in predictions of twenty-first century temperature rise Temperatures will fluctuate about their mean climatic state owing to natural internal variability. We include decadal variability in our uncertainty analysis, but we do not consider sub-decadal variations that would be additional to the uncertainty in decadal temperatures presented here. We also consider fluctuations due to potential future changes in solar output and volcanic eruptions. As it is not possible to predict deterministically changes in natural forcings, we estimate natural external variability from simulations of the past 140 years that include these natural forcings.