Code accessibility and code quality across phases of the models of the Coupled Model Intercomparison Project

Abstract. This study extends previous research on CMIP5 models to investigate the reproducibility of climate models within the Coupled Model Intercomparison Project (CMIP). It evaluates the accessibility to the source code of the CMIP models through all their phases, emphasizing the need for public repositories to ensure transparency regarding model input, output, and usage rights, along with an analysis of licenses for compliance with scientific standards. A central focus of the research is the assessment of code quality against best practices. In addition, the study examines the historical evolution of computational and code quality across various phases of CMIP, highlighting progress and improving traceability to support scientific reproducibility. We provide valuable insights for future research, proposing solutions and tools designed to improve replicability and enhance project lifecycles that are applicable not only to CMIP but also to broader scientific contexts.