sharing/connecting categories between blogs

Hi, I need to run 8 blogs all on various subdomains of the same site (it is for a research project involving 8 authors). All eight blogs want to use the same categories, and my question is whether its possible to connect all 8 blogs to shared category index pages somehow?
So that when you clicked a category, it would show all the posts from authors who have assigned that particular category.

I currently have the blogs that I have already set up connected to one database.

I have read up as much as possible, but haven’t found this question anywhere. I am also a few months old in terms of dealing with things web related, so please be kind! Thanks a lot for any help.