We use WP as a CMS and have maintained a client site for

We use WP as a CMS and have maintained a client site for over a year. The ../wp-content/uploads folder has 2,000 files (over 2GB total), and I'm guessing 80% of them are obsolete (no longer referenced by published or private pages). I would like to clean up this directory. Is there a way to easily (or relatively easily) identify orphan files?