Fedora 18 severe overheating HP Envy 4 1002tx in Gnome shell
The issue has been resolved by installing the Gnome Shell Extension - Radeon Power Profile Manager and selecting Set profile to "low" option in it.
More details can be found at: http://smexyyweby.wordpress.com/2013/02/03/resolve-overheating-issue-for-amd-radeon-graphics-card-for-gnome-3-6-in-fedora-18/