Difficulties in Deriving Forecast Probabilities From General Circulation Models and Efforts to Estimate Uncertainty in Future Climate projections

Many decisions taken today will have long term consequences on time scales ranging from one or two decades to 50 or 100 years or beyond. Building design, flood protection measures and water resource planning often involve substantial investment in assets which we hope will be suitable for these very long periods. Over such time periods we know that the earth’s climate will undergo substantial further changes as a result of anthropogenic emissions of greenhouse gases. It is therefore sensible to make such decisions in the context of these changes. This is widely described as climate change adaptation and is in contrast to climate change mitigation where the focus is to limit the extent of changes in the physical climate rather than prepare for expected or inevitable changes ahead.