The mission of the Global Change Master Directory (GCMD) is to enable the scientific community to discover and access Earth science data and services through distributed, integrated information technology systems. The GCMD offers authoring tools to achieve this mission, which conform to international standards. Tools are available to write, directly submit, and directly update metadata records.

The GCMD offers descriptions of Earth science data sets using a specified set of information - known as the Directory Interchange Format (DIF). The GCMD's philosophy for using the DIF is that the specific set of attributes, the content metadata, is the critical set needed for a user to determine if the data sets returned from a database query are those that define viable data sets for the user's needs. Using a specific set of fields also helps to "normalize" the search for data sets through the use of several alternative search engines.

As part of the overall mission, the GCMD supports NASA and NASA partners in related activities:

Support's NASA's Earth Observing System Data and Information System (EOSDIS) and the NASA Federation of Earth Science Information Partners (ESIP) Serves as one of NASA's contributions to the Committee on Earth Observation Satellites (CEOS) by developing and sharing software for the International Directory Network (IDN). Serves as the maintenance body for the Directory Interchange Format standard through the "Interoperability Forum", thus contributing a distinctly valuable service to the Earth science user community. Works with CEOS partners in developing tools aimed at unifying the international communities, such as an Earth science thesaurus. Collaborates with other partners and organizations Creates search "portals" for associated groups who wish to share their data set descriptions through the GCMD and also wish to offer a focused view of their specific data. Assists associated distributed data systems in locating specific data through the use of the GCMD's Applications Programming Interface (API). Develops prototype systems in response to specific needs and requests, such as the Earth Science data-related services. Maintains one of the world's most popular hierarchical set of Earth science keywords. Develops software to improve the discovery of Earth science data and designs software tools to ease the impact on those contributing and updating metadata. Serves as NASA's node for the Federal Geographic Data Committee's (FGDC) Clearinghouse , offering NASA's data set descriptions as part of the National Spatial Data Infrastructure.

The Global Change Master Directory staff plans its work in line with its mission statement, in conjunction with the goals and responsibilities as the American Coordinating Node of the Committee on Earth Observation Satellites' (CEOS) International Directory Network (IDN), the shared goals with EOSDIS, and in response to feedback from the GCMD Science User Working Group. GCMD accomplishments can be viewed in the State of the GCMD Report .