In aviation, and particularly in the sport of gliding, a stick thermal is an illusion that the glider is climbing in a thermal when, in fact, the upward movement of the glider is caused by nothing more than the pilot pulling backwards on the control stick, causing the aircraft to climb, but lose airspeed.
They can use this to find the strongest area of lift in the thermal.
So the variometer shows zero rate of climb, and does not indicate the presence of the thermal.
A total energy compensated variometer will show the actual rate of climb of the thermal, regardless of the movement of the aircraft.
You can help Wikipedia by expanding it.This air sports-related article is a stub.