If you have a fear of flying, there might be an intensification of this feeling as you board the plane, and again when you take off. That is, your feelings of fear might increase or "intensify."
An intensification is an increase in strength or magnitude (or intensity). Agricultural intensification is an increase of productivity per acre. The intensification of a conflict, as in a war, usually means an increase in fighting. Gender intensification is an increasing preference by boys for "boy things" and by girls for "girl things."