On another thread bbr2314 has stated that IPCC RPC is "useless".
To make it clear I assume we are talking about this:
http://sedac.ipcc-data.org/ddc/ar5_scenario_process/RCPs.htmlI disagree. I could go into a long and detailed defence of the RCP - also listing the flaws I know of in the RCP (There are several - there always will be in a future modeling project of this type) but I don't see why I should have to; To prove something is useless it is not necessary to list all the things it is useful for, it is required to state what the assumed purpose of that something is and why it doesn't meet that purpose, never has done and never will.
All I will say is that the general methodology follows what James Hansen did in the 1980s with 3 "pathways" (Which 30 years later has been generally agreed on as a useful way to frame the model data and questions which we need answers to) and the RCP includes (mainly - nothing is perfect!) all the latest model data known to required margins of error. Given that heritage, to say RCP is "useless" is a pretty extreme statement which requires pretty extreme evidence/argument to back up that statement (imho).