Abstract
AbstractMore than 40 model groups worldwide are participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), providing a new and rich source of information to better understand past, present, and future climate change. Here, we use the Earth System Model Evaluation Tool (ESMValTool) to assess the performance of the CMIP6 ensemble compared to the previous generations CMIP3 and CMIP5. While CMIP5 models did not capture the observed pause in the increase in global mean surface temperature between 1998 and 2013, the historical CMIP6 simulations agree well with the observed recent temperature increase, but some models have difficulties in reproducing the observed global mean surface temperature record of the second half of the twentieth century. While systematic biases in annual mean surface temperature and precipitation remain in the CMIP6 multimodel mean, individual models and high‐resolution versions of the models show significant reductions in many long‐standing biases. Some improvements are also found in the vertical temperature, water vapor, and zonal wind speed distributions, and root‐mean‐square errors for selected fields are generally smaller with reduced intermodel spread and higher average skill in the correlation patterns relative to observations. An emerging property of the CMIP6 ensemble is a higher effective climate sensitivity with an increased range between 2.3 and 5.6 K. A possible reason for this increase in some models is improvements in cloud representation resulting in stronger shortwave cloud feedbacks than in their predecessor versions.
Highlights
Climate model simulations are coordinated as part of the World Climate Research Programme's (WCRP) Coupled Model Intercomparison Project (CMIP) since the early 1990s (Eyring, Bony, et al, 2016; Meehl et al, 1997, 2000, 2005, 2007; Taylor et al, 2012)
We evaluated multimodel ensembles from three different phases of CMIP, namely CMIP3, CMIP5 and CMIP6
Improvements or changes in model performance from one CMIP phase to the are typically a combination of different factors such as an increasing spatial and vertical resolution, a more complete and a more detailed representation of individual Earth system models (ESMs) components and the inclusion of additional Earth system processes that could be added in recent years as increasing computing power became available
Summary
Climate model simulations are coordinated as part of the World Climate Research Programme's (WCRP) Coupled Model Intercomparison Project (CMIP) since the early 1990s (Eyring, Bony, et al, 2016; Meehl et al, 1997, 2000, 2005, 2007; Taylor et al, 2012). An important question to answer is how these new simulations compare to previous generations of CMIP ensembles, and whether systematic biases detected earlier are reduced or remain. A systematic evaluation of models results by comparisons with observations and reanalysis data is commonly seen as an important prerequisite to building up confidence in the models' future climate projections (Flato et al, 2013). This more general assessment of model performance is complimented with approaches that use observations to constrain the uncertainty in multimodel projections or feedbacks with observations (Eyring et al, 2019).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
