MacBook Pro fan whirring non-stop after upgrading to MacOS Sierra

[iMore Question]

This is driving me bonkers and I've tried all the recommended steps to stop this issue but it is my third day with the fan whirring non-stop. It happens when I start up Safari and do my usual thing of logging on to my usual stuff and surfing. I've checked the Activity Monitor as suggested on many websites and it is usually the "safari web content not responding" or a "kernel task" that's causing the surge in energy/CPU usage. I've tried the SMC re-set 3-4 times now and that usually works for the day but the fan starts up again the next day after I start up the laptop. I've also tried disabling the WebGL and plug-in options but that doesn't make any difference and then I've got to enable them for certain sites anyway. Does anybody have any further ideas that would rectify this permanently? The other option of course is to downgrade back to El Capitan, which will be frustrating. Thank you!

 

[Just_Me_D]

How much RAM does your MBP have installed?

 

[BlackNightmare]

It may be some issue crated by the upgrading procedure. Before the downgrade, you can try and create a booth drive of Sierra, and, after a backup though Time Machine or other backup software on an external hard drive, perform a clean install of the software, wiping clean all your MacBook