All hail Robert Boyle, the inventor of the atmosphere. Really? Well, he was the first to note that the pressure and volume of a gas are inversely proportional at a constant temperature and that led us to the . . .
— James Albright
. . . "standard atmosphere" which sets the starting point for all things to do with aircraft performance.
1 — International Standard Atmosphere (ISA)
- Earth's long-term average global temperature is 59°F (15°C)
- The average decrease in temperature with altitude through the lowest 11 km (approx. 36,000 ft) is roughly 6.5°C per 1000 m (3.6°F or 2°C/1000 ft).
Aeronautical Information Manual
Shein, Karsten, "Common Sense and Winter Flying," Professional Pilot, Nov 2011