Keywords from the Global Change Master Directory (GCMD).
Reference: Global Change Master Directory (GCMD). 2016. GCMD Keywords, Version 8.4. Greenbelt, MD: Global Change Data Center, Science and Exploration Directorate, Goddard Space Flight Center (GSFC) National Aeronautics and Space Administration (NASA). URL:http://gcmd.nasa.gov/learn/keywords.html
Please note that we are using the respective vocabularies essentially as they are provided from the respective maintainers. In some cases we made slight formal modifications, like adding language attributes "xml:lang" to <skos:prefLabel>, <skos:altLabel> etc. or changed <dc:description> to <skos:definition> for the reason of internal homogeneity. IN NO CASE we made conceptual changes like e.g. reordering of hierarchical relations (even if in some rare cases we thought it would make sense). So if you find questionable relations when browsing through the respective vocabularies, please send a message to the respective maintainers.