CMIP5 scientific gaps and recommendations for CMIP6

The scientific gaps identified in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) that guided the experiment for its next phase, CMIP6, are identified. CMIP needs to create a scien�tific framework for a set of coordinated multimodel experiments designed to increase our understanding of the climate system. At the same time CMIP needs to remain relevant to the broader climate change community. CMIP5 incorporated new paradigms for developing future emission scenarios, introduced experiments to explore carbon climate interactions, and used high-resolution atmosphere-only models to provide more detailed regional climate change information. The future climate change problem was defined by time scale in terms of near-term and long-term. A survey of the various parts of the climate community subsequent to CMIP5 and the Fifth Assessment Report of the IPCC revealed a number of challenges and gaps in the CMIP5 process. Poor quantification and understanding of radiative forcing have been a long-standing problem within CMIP and will be revisited with new approaches in CMIP6, including more coordinated representation of the atmospheric aerosol and land surface processes and much more detailed online and offline intercomparison activities. The problems of comparing models to observations when the signals are small relative to the natural climatic variability, as well as trying to understand and predict the variability on longer than annual time scales will also be addressed in CMIP6. CMIP6 will consist of individual CMIP6-endorsed MIPs that focus on specific scientific themes.