The Evaluation of Forecasts

The ultimate goal of climate dynamics is the prediction of climate variability on interannual to interdecadal and longer timescales. Two necessary, but not sufficient, conditions for the usefulness of such forecasts is that they have real skill in discriminating one forecast situation from another and that this skill is known in advance by the user. Two “no-skill” forecast schemes would be random forecasts or constant (e.g. fixed climatology) forecasts. An additional factor relevant to a scheme’s usefulness is its efficiency — in other words its skill with respect to more simple forecast schemes (like persistence of existing conditions).