To add to the above comments, but Rich Hickey goes into the relationship between ClojureScript and Google Closure tools in his intro of ClojureScript. http://blip.tv/clojure/rich-hickey-unveils-clojurescript-5399498

Basic gist is in the comments:

> [Robert Harvey: ClojureScript is a compiler for Clojure that emits JavaScript ... and is design to emit ... code [that] is compatible with the advanced compilation mode of the Google Closure optimizing compiler.][1]


  [1]: http://programmers.stackexchange.com/questions/139703/getting-started-with-clojurescript-and-google-closure?newsletter=1&nlcode=18924|ae92