Programmatic access to CCI data is available through the following methods.

OpenSearch

Access all data of the CCI Open Data Portal through OpenSearch, a suite of web-based search engine and search protocol standards. An OpenSearch description provides the web interface of the CCI Open Data Portal search engine -
https://archive.opensearch.ceda.ac.uk/opensearch/description.xml

THREDDS

A THREDDS web server provides access to data and metadata on the CCI Open Data Portal via the Web Map Service (WMS) and Web Coverage Service (WCS) standards of the Open Geospatial Consortium and the Open-source Project for a Network Data Access Protocol (OPeNDAP) standard.
https://data.cci.ceda.ac.uk/

Earth System Grid Federation

CCI Obs4MIPs datasets are available through the Earth System Grid Federation (ESGF). These provide observational CCI products technically aligned with climate model data, specifically that made available from the Coupled Model Intercomparison Project (CMIP). ESGF provide a RESTful API.
https://esgf.ceda.ac.uk/esg-search/search/?query=CCI

FedEO

The CEOS Federated EO Gateway (FedEO) Clearinghouse STAC index provides interoperable access, following ISO/OGC interface guidelines, to Earth Observation metadata. The FedEO service periodically ingests the latest CCI Open Data Portal catalogue of all CCI datasets.

https://radiantearth.github.io/stac-browser/#/external/fedeo.ceos.org/series/eo:organisationName/CEDA

ESA Data Discovery Portal

The ESA Data Discovery Portal crawls publicly available metadata of ESA datasets and indexes the metadata, providing a unified view of all ESA data holdings including in a machine-readable way so it can be processed by search engines that index structured data.
https://data.esa.int/

CCI Data Policy

The CCI Data Policy ensures free and open access to CCI data. The policy is available here.

CCI Data Standards

The CCI Data Standards are community-driven requirements ensuring consistent essential climate variable (ECV) data production across the CCI programme. Version 2.3 is the latest. The requirements include data production conformance to the network Common Data Form (netCDF) format, the Climate and Forecasting (CF) metadata conventions, the Attribute Convention for Data Discovery (ACDD), and Infrastructure for Spatial Information in the European Community (INSPIRE) compliant discovery metadata.

CCI Ontology

To ensure consistency where the same global attributes apply to all CCI essential climate variables (ECVs), and to avoid different terms being used for the same entity, relevant terms have been gathered in a CCI Ontology defining all CCI entities and the relationship between those entities, including CCI project, platform, sensor and institution. For example, the ontology defines common entities for the satellite platforms used across the CCI projects in their data production.