CFMIP is a WCRP endorsed project which aims to improve the understanding and evaluation of clouds, cloud feedbacks and changes in regional-scale circulation and precipitation.
CFMIP started in 2003 and its first phase (CFMIP-1) organised an intercomparison based on perpetual July SST forced Cess style +2K experiments and 2xCO2 equilibrium mixed-layer model experiments containing ISCCP simulator in parallel with CMIP3 (McAvaney and Le Treut, 2003). Results from CFMIP-1 had a substantial impact on the evaluation of clouds in models and in the identification of low level cloud feedbacks as the primary cause of inter-model spread in cloud feedback, and featured prominently in the fourth and fifth IPCC assessments.
The subsequent objective of CFMIP-2 was to inform improved assessments of climate change cloud feedbacks by providing better tools to support evaluation of clouds simulated by climate models and to understand cloud-climate feedback processes. CFMIP-2 organized further experiments as part of CMIP5, introducing seasonally varying SST perturbation experiments for the first time, as well as fixed SST CO2 forcing experiments to examine cloud adjustments, and idealized ‘aquaplanet’ experiments to establish the contributions of land and zonally asymmetric circulations to cloud feedback uncertainties (Bony et al., 2011). CFMIP-2 also introduced satellite simulators to CMIP via the CFMIP Observation Simulator Package (COSP), not only the ISCCP simulator, but additional simulators to facilitate the quantitative evaluation clouds using a new generation of active RADARs and LIDARs in space. Additionally CFMIP-2 introduced into CMIP5 process diagnostics such as temperature and humidity budget tendency terms and high frequency ‘cfSites’ outputs at 120 locations around the globe. CFMIP also organized a joint project with the GEWEX Global Atmospheric System Study (GASS) called CGILS (the CFMIP-GASS Intercomparison of LES and SCMs) to develop cloud feedback intercomparison cases to assess the physical credibility of cloud feedbacks in climate models by comparing Single Column Models (SCM) versions of GCMs with high resolution Large Eddy Simulations (LES) models. Additionally CFMIP-2 developed the CFMIP-OBS data portal and the CFMIP diagnostic codes repository.
Early studies arising from CFMIP-2 include numerous model evaluation studies using COSP, studies attributing cloud feedbacks and cloud adjustments to different cloud types, and the finding that idealized ‘aquaplanet’ experiments without land or Walker circulations are able to capture the essential differences between models’ global cloud feedbacks and cloud adjustments. Process outputs from CFMIP have also been used to develop and test physical mechanisms proposed to explain and constrain inter-model spread in cloud feedbacks in the CMIP5 models. CGILS has demonstrated a consensus in the responses of LES models to climate forcings and identified a number of shortcomings in the physical representations of cloud feedbacks in climate models. Additionally the CFMIP experiments have, due to their idealized nature, proven useful in a number of studies not directly related to clouds, but instead analyzing the responses of regional precipitation and circulation patterns to CO2 forcing and climate change. Studies using CFMIP-2 outputs from CMIP5 remain ongoing and many further results are expected to feed into future assessments of the representation of clouds and cloud feedbacks in climate models. For a list of publications arising from CFMIP-2, please refer to the CFMIP publications page.
In 2015, CFMIP proposed a new set of coordinated experiments for CMIP6, and was subsequently endorsed as a CMIP6 project. For more details, please refer the the CFMIP website at http://cfmip.metoffice.com.