Scientists continue to be confounded by the various data types, formats and systems used for Earth Science data. For example, regional atmospheric air pollution models have to deal with over 20 different data sets. These data come in formats ranging from HDF to GRADS to GIS to MCIDAS to AIRS, each of which has a large manual describing the structure and format of the data. It is very difficult for individual scientists or even scientific groups to have expertise at their disposal to deal with each of these data types. Often important new data is not incorporated if it is in a format that is new to the scientists or their groups. The Earth Science Markup Language (ESML) provides an elegant solution to this problem. ESML is a specialized markup language for Earth Science that allows data descriptions to be easily written. ESML is based on the eXtensible Markup Language (XMLTM), and is unique in that it not only describes the content and structure of a data set, but also provides semantic information needed for the end user application to effect a runtime interpretation of the data. Thus, ESML facilitates the development of dataset independent search, visualization, and analysis tools without requiring data to be in any particular format or formats. ESML also allows wider interoperability of Earth Science data services, enabling Earth Scientists to author, discover, and interpret Earth Science information, and to work with data in a variety of formats. This paper will describe ESML, how it can be used by scientists to describe their data sets, and its advantages to both scientists and application developers.