The extent to which the future state of a system may be predicted based on knowledge of its current and past states. Predictability is inherently limited, since knowledge of the system’s past and current states is insufficient, and the models that utilize this knowledge to produce a prediction are generally imperfect. Even with arbitrarily accurate models and observations, there may still be limits to the predictability of a physical system.
A collection of model simulations characterizing a climate prediction or projection. Differences in initial conditions and model formulation result in different evolutions of the modelled system. In the case of climate forecasts, these simulations may give information on uncertainty associated with model errors and errors in the initial conditions. For projections of longer-term climate change, these simulations provide can provide information on uncertainty associated with model errors and with internally generated climate variability.