The temporary bump in TOT is due to the engines having to run the RPM up to the new values.
Once the new, higher RPM is established, the TOT will return to close to the original value.
As 212man stated, the value of this is that power is torque times RPM. 100% torque at 100% RPM will equal a certain horsepower, where 102% RPM AT 100% torque will be 2% more power.
Power is needed to overcome the drag of the blades to provide the lift you need. Higher RPM means slightly less angle of attack is needed to produce the same lift than a lower RPM, so the drag will be slightly less than trying to produce the same lift at the lower RPM, and you will magically rise into the air...