The probabilistic projections combine information from several collections of earth system climate models, including the HadCM3 family of Met Office Hadley Centre climate models, and earth system climate models from other climate centres contributing to CMIP5 (Coupled Model Intercomparison Project Phase 5) and the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013).

The leading sources of modelling uncertainty in the atmosphere, land surface, ocean, sulphur cycle, and terrestrial carbon cycle components of the climate system are sampled, and simulated responses are weighted by the likelihood for predicting a large multivariate set of climate observables. Observationally constrained uncertainty estimates for ranges of future climate are provided in the form of probability distribution functions or large sets of probabilistic realizations, for the RCP2.6, RCP4.5, RCP6.0, RCP8.5 and SRES-A1B emission-driven scenarios.