the climbing rate gauge should have HUGE variations caused by atmosphere

[jf1981]

Originally Posted by zipper

In flight, corrections must (practically) be sent by radio from weather or control centers and be relevant for the aircraft's location.

Above 3000 ft agl we use standard reference 1013,25 (29.92), there would no point keeping accurate true altitude (some areas of the world, even impossible to know local pressure), only accurate pressure altitude is needed.