Variability of Atmospheric Pressure
One can say with certainty that atmospheric pressure, while reasonably constant now, was much higher in the past. Every reasonable consideration supports higher past atmospheric pressure. The entire evolution of Earth including life’s transition to modern life supports higher past atmospheric pressures- higher pressures that have dwindled to current levels. As a result, past surface temperatures were at higher average levels. Cooler modern temperatures are the reason cold-blooded reptiles that were successful during the Mesozoic must bask in sunlight for energy even in modern tropical climates. How well would basking reptiles survive in the predator rich Mesozoic?
An atmospheric drop explains the deluge of Noah’s flood (Noah’s Ark).