A dataset often contains many geodata layers representing the same kind of measurement, but for different values of some parameters - time periods, models or scenarios, different species, etc.  A value must be chosen for each such parameter in order to select a specific layer  or raster which associated a single value with each geographic location (cell).  The parameters or choices relevant to selecting layers from  this dataset are described here.
Multi-year Ranges: 
120,000 yr BP, 21,000 yr BP, 6000 yr BP, 1950-2000, 2050, 2070