Thanks for the great comments, all. Thanks PIF for that link. And I think Medved in absentia for all those old topics about how giant critters could function. :’)
There’s been some suggestion that there was a higher CO2 level in the atmosphere (and not just a little higher, orders of magnitude more) in order to A) get funding for research from the “global warming” agenda, and B) try to explain how dinos were found from pole to pole (drifting continents can’t account for it, the former dino ranges weren’t in the temperate or subtropical or tropical zones).
A thicker atmosphere transports heat from here to there more efficiently. The global temperature would be more uniform even in the absence of a greenhouse effect.
With the current atmospheric thickness, sea level temperatures range from ~-140°F to ~140°F, with a global average of about 60°.
Without actually running the numbers (mostly because I don’t have a clue how to do it) I would not be surprised if an atmosphere twice as thick were 20° warmer on the average, and had a range 3 times narrower, 30° to 115°. Very pole-to-pole survivable even for a reptile.
You, of course, can make up your own numbers...