In the rekognition
of the uncertainties, the IPCC Good - Practice - Guidance - Paper on
using climate model results offers some
wise advice (first
bullet point under section 3.5 on p. 10): the local climate change scenarios should be based on (i) historical change, (ii) process change (e.g. changes in the driving circulation), (iii) global climate change projected by GCMs, and (iv) downscaled projected change.