A group of UKCP09 25 km grid squares for which a single UKCP09 probabilistic climate projection is available.
The probabilistic nature of the UKCP09 climate projections means that the projected changes at a particular probability level (for example, 90%) for multiple grid squares cannot simply be averaged together (as was possible with previous UK climate projections like UKCIP02).
For this reason projections in UKCP09 are also given for three sets of aggregated areas (administrative regions and river basins over land, and over the sea). The definition and extent of which were informed by consultation with the UKCP09 Users’ Panel. Probabilistic climate projections are provided as an average value across all UKCP09 25 km grid squares that comprise each aggregated area.