Pretty simple. Compressed Overlay Distortion. Squeeze like hell in the head voice until you create so much noise in the upper vocal tract that you have distortion. Effective, but hella fatiguing and if you are not doing other things properly in your technique, it can destroy your voice.
This performance is awful. It is the head voice he used to use, without the compressed overlay, resulting in essentially, falsetto. Why he can't squeeze the hell out of it like he used to back in the day at least for one night, IDK.
Training for this technique is found HERE: