Is there any way to enable inverse scrolling like on Mac OSX?
You can use "Natural Scrolling" to have a system wide inverse scrolling.
What is Natural Scrolling?
Natural Scrolling is a GNOME Applet allowing you to reverse the direction of scrolling. You push your fingers upwards to move the page content upwards (and downwards for downwards) just like on iOS devices. Don't move scrollbars anymore but your file.
Install Natural Scrolling:
Natural Scrolling can be installed from its PPA.
Hit Alt+Ctrl+T to open terminal and run following commands:
sudo add-apt-repository ppa:zedtux/naturalscrolling sudo apt-get update sudo apt-get install naturalscrolling
How to enable Natural Scrolling?
Once installed, Hit Super key (Windows key) to open Unity dash and search for "natural scrolling" and open it. You'll see a new indicator in Unity panel, Click on it and select your device. In the preferences you can set it to start at login. That's it!
The Natural Scrolling application referred to in Basharat Sial's answer does not fix natural scrolling in certain system windows.
As an alternative, I recommend the guide provided in this answer. You won't need the natural scrolling application anymore when you use his guide.
You can also use Ubuntu Tweak tool to enable natural scrolling (misc settings)
Official homepage with .deb distributive: http://ubuntu-tweak.com/