The Coupled Model Intercomparison Project, which began in 1995 under the auspices of the World Climate Research Programme (WCRP), is now in its sixth phase (CMIP6). CMIP6 coordinates somewhat independent model intercomparison activities and their experiments which have adopted a common infrastructure for collecting, organizing, and distributing output from models performing common sets of experiments. The simulation data produced by models under previous phases of CMIP have been used in thousands of research papers (some of which are listed here), and the multi-model results provide some perspective on errors and uncertainty in model simulations. This information has proved invaluable in preparing high profile reports assessing our understanding of climate and climate change (e.g., the IPCC Assessment Reports).
Also see CMIP6 Data Holdings Summary for a summary table showing available experiments and models.
The following links will lead to additional information about CMIP6:
The complete archive of CMIP6 output is made available for search and download via any one of the following portals:
If you encounter slow responses from one search interface, you might try one of the other portals (perhaps one near you). Also note that the datasets themselves are stored (and partially replicated) on a federated system of data nodes, and again you may find differences from node to node in download speeds.