Knowledgebase : Global Change Master Directory (GCMD)
The GCMD holds more than 35,000 Earth science data set and service descriptions, which cover subject areas within the Earth and environmental sciences.  The project mission is to assist researchers, policy makers, and the public in the discovery of and access to data, related services, and ancillary information (which includes descriptions of instruments and platforms) relevant to global change and Earth science research.  Within this mission, the directory also offers online authoring tools to providers of data and services, facilitating the capability to make their products available to the Earth science community.  In addition, citation information to properly credit data set contributions is offered, along with direct links to data and services.  As an integral part of the project, keyword vocabularies have been developed and are constantly being refined and expanded.  These vocabularies are also used in other applications within the broader scientific community.  Users may perform searches through the Directory’s website using controlled keywords, free-text searches, map/date searches or any combination of these.  Users may also search or refine a search by data center, location, instrument, platform, project, or temporal/spatial resolution.

If you have a data set or service that is relevant to global change, consider advertising to the scientific community through the GCMD using the docBUILDER metadata authoring tool. The GCMD is not limited to governmental datasets nor is it restricted to freely distributed data. It is open to anyone having data or services that may advance our understanding of Earth and its systems, from the smallest, micro-scale dataset to the largest global satellite downloads. All are welcome.

In addition, you as the data holder both maintain control of the data and its distribution (the GCMD is a data locator) as well as receive credit for the data. For holders of a great deal of data or services, the GCMD is a convenient way to maintain a descriptive index of your data or service for your own reference as well. Best of all, both searching for and including dataset and service descriptions is completely free.

To add or modify descriptions in the GCMD, visit

A GCMD "portal" is defined as a virtual subset of the complete content of the directory. Recognizing the importance of customization for partner organizations, the staff generates subset views of the GCMD directory through "conceptual" portals. Portals have facilitated focused views for organizations to maintain and document their data in one place (within the directory), without duplicating the effort to create another online directory.

Many organizations acknowledge the importance of metadata related to their area of interest but do not have the resources to manage the content. Portals offer a targeted science or application-specific focus for other agencies, science focus groups, consortia, etc.

Portals may be branded with the logo of an organization, while offering the full functionality of the GCMD search engine and tools.

Using a portal (of which content is a "virtual subset") is advantageous in that as metadata are added to the subset, they are also freely available from the GCMD's comprehensive search pages for scientists in other disciplines to access and use.

View the list of GCMD portals at

The GCMD has made it very easy for the public to locate the data sets they desire. All the metadata are accessible via several search interfaces.

Search Options:

  • Earth Science Keywords: Search results can be modified Science discipline, geographic location, platform/source, or instrument. Or try the map/date combo data search.
  • Full-Text Search: This allows a query on user specified keywords. This can be of use when searching for metadata on specific topics (e.g., El Niño or Global Warming).

A tutorial on the new search functionality is available at

The GCMD contains descriptions of data sets covering all disciplines that produce and use data to help us understand our changing planet. The GCMD includes metadata from disciplines including atmospheric science, biology, oceanography, ecology, geology, hydrology, and human dimensions of climate change. This interdisciplinary focus is aimed at researchers exploring the interconnections and interrelations of mulitdisciplinary variables on global changes (e.g., How global warming may impact human health).

The full list of science disciplines is as follows:

  • Agriculture
  • Atmosphere
  • Biological Classifications
  • Biosphere
  • Climate Indicators
  • Cryosphere
  • Human Dimensions
  • Land Surface
  • Oceans
  • Paleoclimate
  • Solid Earth
  • Spectral/Engineering
  • Sun-Earth Interactions
  • Terrestrial Hydrosphere
Earth Science Data Set Descriptions Earth Science Data Service Descriptions