The dataset in question is the "ERA5 hourly data on single levels from 1940 to present," part of the ECMWF's fifth-generation reanalysis product. It provides hourly estimates for various atmospheric, ocean-wave, and land-surface quantities globally since 1940, available on a regular latitude-longitude grid with a resolution of 0.25° x 0.25° for the atmosphere and 0.5° x 0.5° for ocean waves. The data is derived from combining model outputs and observations using advanced data assimilation techniques, ensuring a globally consistent and complete dataset. ERA5 includes precomputed uncertainty estimates through an ensemble mean and spread, essential for assessing data reliability. While daily updates are provided with a latency of about five days, users are informed if significant issues arise in the early release. The dataset is optimized for efficient access and retrieval, making it valuable for climate research, monitoring, and application development requiring high-resolution historical data.