GPU temperature is above 70 C, and CPU fan is above 2400 rpm I've had my iMac for two years now. I play a lot of games and watch a lot of HD videos. In the past week, the computer has gotten a lot hotter than usual and it stutters a lot, and I feel like the two are related.

Today while playing a game I noticed that the GPU Diode reached 70 C (using iStat Pro), which I have never seen before. Therefore, the CPU fan was at 2400 rpm.

I play a lot of games, including this same one, and I have never seen the GPU this hot before, and almost never hear the fans running so loudly and so rapidly. (I can't even recall a time when I could very clearly hear the fans running.)

Could all this be a sign to a more bigger problem?
Yes, it could. Some things that could be happening, in order of probability:


Your computer's innards could be dusty. This is the the most likely cause, and is easily remedied by unplugging your computer, taking it outside or into the garage,  and using a compressed air canister to blow out all of the dust in the vents. (If you have allergies or asthma, I suggest wearing safety goggles and/or a mask. Also, the can will get very cold, so wearing gloves is probably a good idea as well.)
A(n unrelated) background process could be taking up a lot of CPU. What was the CPU percentage? Did you check if any other processes were running? If this is happening often, it could be that some other program (Software Update, Finder, Skype, etc.) is trying to run in the background, and is experiencing errors that cause it to hog memory.
The game and/or media player you use may have recently undergone an update that consumes significantly more CPU and/or memory and/or disk usage that you are used to. If you ran a software update in the last two or three weeks, or if the game and/or media player performs automatic updates, this may explain the problem. (If this is the case, and the issue is very bothersome, you can probably contact the vendor to get the previous version.)
A government entity could be spying on you through your computer.