NASA Earthdata
NASA Earthdata is the single entry point to NASA's Earth science holdings, covering the atmosphere, ocean, land, and cryosphere, plus assessments of how humans interact with the environment. The data comes from dozens of satellite missions, airborne campaigns, and ground stations.
You can search and pull data programmatically through the Common Metadata Repository, the search API that lets you discover and access all 12,400+ datasets using spatial, temporal, and keyword filters. The data is openly available without restriction, though you need a free Earthdata Login to download.
Related sources
Copernicus (EU Earth Observation)
The EU's flagship Earth observation programme. The Copernicus Climate Change Service portal provides authoritative information about past, present, and future global climate, derived from Sentinel reference products alongside other satellite observations and in-situ measurements.
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.
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.