What is the difference between CMIP5 and CMIP6?
In short: CMIP5 and CMIP6 are successive phases of the Coupled Model Intercomparison Project, not two interchangeable versions of one dataset. CMIP5 future experiments mainly use Representative Concentration Pathways (RCPs), whereas CMIP6 future experiments use Shared Socioeconomic Pathway (SSP) combinations. CMIP6 also includes newer model generations, updated forcings, revised experiments, and different data conventions.
Scenario and experiment differences
An RCP label and an SSP label may have similar end-of-century forcing levels, but their socioeconomic assumptions, emissions pathways, and experiment definitions are not identical. Comparisons should use the appropriate historical and scenario experiment from the same model generation.
Data-handling differences
Variable names can look similar across phases, but calendars, grids, units, ensemble labels, file metadata, and available periods may differ. Each dataset should be checked and harmonized before evaluation or downscaling.
Process either CMIP5 RCP data or CMIP6 SSP data with the compatible SD-GCM desktop workflow.