1/ check out the airplane performance at the higher temperature (full thrust).
2/ though the temperature is actually somewhat lower, we set that previously 'checked out' thrust, by not actually pushing the thrust levers all the way up, (hence the lower work-load).
3/ we know the performance will be sufficient at that lower thrust setting because we checked it out. (thrust, ASDA etc)
4/ in actual fact, the airplane performance will be better than that 'checked out' performance, because the airframe will actually respond better in the cooler environment.
That's about as simple as I can manage!
Cheers...FD...
