My iPhoto library takes way too much space on my Mac Air. Can I upload it to the iCloud? So, the iPhoto library (not to be confused with the "Photos library") takes almost 30 gigs on my 250 gb macbook air. I am curious, I've managed to upload the Photos library to the iCloud reducing it's size to mere 3 GB. Is there any way I can do the same trick with the iPhoto library? As far as I can understand, it's the location for my older photos, taken and uploaded before apple rolled the new photos library in?
No, you can’t. In order to do this, you have to migrate from iPhoto to Photos.

Photos contains the integration with iCloud storage that can offload to your iCloud account on demand to free up local space.