How to pass variable to application controller from emberjs child controllers?

Question

Ember.js

The application.hbs template contains the {{pageTitile}} variable.
It is necessary to pass values ​​from child templates/controllers to it.
For example, we load a post (posts/:post_id) and pass the variable {{pageTitile}}, which is in the site header, the title of the post.
Tried to hobble this moment on crutches:

Failed. Yes, and I want to know how Amber offers to solve such problems.
You can pass a variable from each controller to the parent one, and accept it in the parent one, but there are about 50 page templates in the project, the parent controller will be completely cluttered.
Maybe there is an elegant solution?