Copernicus (EU Earth Observation)
Copernicus is the European Union's Earth observation programme, built on the Sentinel family of satellites. Its Climate Change Service portal offers authoritative information about past, present, and future global climate, drawing on Sentinel reference products, other satellite observations, and in-situ measurements taken on the ground.
Access is free, full, and open under the Copernicus licence. That licence lets you reuse the data for any purpose, including commercial use, as long as you attribute Copernicus as the source.
Related sources
Met Office DataPoint / CEDA
The Centre for Environmental Data Analysis hosts UK atmospheric and Earth observation data, including Met Office archives, climate model outputs, and satellite data.
NASA Earthdata
The home for full and open access to NASA's Earth science data collections. The umbrella portal for the largest collection of freely available Earth science data in the world, with over 12,400 datasets spanning land, ocean, atmosphere, and cryosphere, collected by satellite missions, airborne campaigns, and ground stations.
NOAA Open Data Dissemination (NODD)
Free, full, and open access to NOAA data through partner platforms including Amazon Web Services, Google, and Microsoft Azure. Covers climate data records and atmospheric, oceanic, and terrestrial datasets from one of the largest climate archives in the world.
World Resources Institute
Free environmental data for GIS, climate research, and sustainability projects. Includes Global Forest Watch and other environmental monitoring datasets.