Navigate terminal scrollback using keys
There are shortcuts for Page Up/Down and Line Up/Down in Terminal. You can find them under View menu item. For Page Up press ⌘ cmd+⇞ Page Up, for Line Up press ⌘ cmd+⌥ alt+⇞ Page Up.

Edit: you can get ⇞ Page Up on Macbook by pressing Fn+↑ Up Arrow.