The full-featured and CoreTrustSeal certified long term archiving service LTA WDCC (World Data Centre for Climate) at DKRZ (German Climate Computing Center, Hamburg) offers long term preservation for datasets relevant for climate and Earth System research. The WDCC collects, stores, and disseminates Earth System data with a focus on climate simulation data and climate related data products. It has established itself as a staple infrastructure for the global climate modelling research community. Data preservation in LTA WDCC is preceded by a thorough technical quality control and provides intense data curation for storage periods longer than 10 years. During the preservation period, long term findability, searchability and reusability of the data are ensured. Long term findability of the curated data is enabled through the possibility of assigning DataCite DOI’s to archived datasets. The data undergo additional quality checks before being eligible for DOI assignment. This process is performed in close collaboration with the data providers. The focus of these quality checks is to ensure the unambigous (inter-)disciplinary reusability of the preserved datasets and includes checking for proper documentation, adherence to domain specific (meta)data standards, uncertainty analysis and cross-referencing. Only then can a high level of reusability of the data be achieved, justifying the involved effort. The perceived need for research data repositories to comply with the 2016-published FAIR Guiding Principles has motivated us to perform an even-handed and systematic self assessment of LTA WDCC FAIRness. Due to lack of a standardised evaluation framework, this assessment reflects our specific, albeit objective, interpretation of the principles. Our assessment, published on the DKRZ webpages, shows that the native philosophy behind DKRZ’s LTA WDCC service – especially the focus on reusability – reflects the FAIR Guiding Principles by design and even goes beyond them by ensuring very long-term (>10 years) preservation and therefore reusability of archived data.