http://www.wmo.ch/pages/prog/hwrp/documents/EXPERTMEETINGWAT...

The meeting showed that climate predictions and seasonal climate outlooks at present have the highest potential to be more readily used while predictions of climate variability and change, while inherently useful, are not yet ready to be applied from an engineering point of view and other techniques, such as using multi-model ensembles and downscaling techniques are required to improve prediction skills to reduce large uncertainties.
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In order to statistically improve on climate prediction uncertainties, the use of multi-model ensembles has shown to be useful. However, with regard to information on the variability in the ensemble distribution, the there is little evidence that there is any information in the ensemble beyond the shift in the ensemble mean. For application purposes, most information is contained in the ensemble mean.