legacy/src/main/java/ucar/nc2/NetcdfFileWriteable.java
public Attribute addGlobalAttribute(String name, String value) {
    return addGlobalAttribute( new Attribute(name, value));
  }
public Attribute addGlobalAttribute(String name, String value) {
    return addGlobalAttribute( new Attribute(name, value));
  }
Add a Global attribute of type String to the file. Must be in define mode.

@param name  name of attribute.
@param value value of atribute.
@return the created attribute