Global Admin User?

I suspect this has been asked before, however I can’t seem to find it.

Can I set up a ‘global’ admin who when logged in, would be able to administer ALL the networks that have been created under a single WP install?

Right now, each of my networks has the same admin user, and I must log in to each network in order to administer it. It would be nice if I only had to log in once, and administer any of the networks that I have set up.

Thanks.