“CO2 has a bonafide hockey stick, probably the highest in millions of years although that can’t be proven since the ice cores have such poor resolution. But certainly a sharp rise since about 1950 using a combination of high res ice cores from the last 20k years from Greenland and the atmospheric measurements.”
Disagree. Nothing bonafide about it. CO2 isn’t a ‘greenhouse’ gas. CO2 definitely settles, there’s no science saying it does otherwise. We had kickplates in our CO2 rooms PRECISELY because it settles.
Smokestacks are there to ensure whatever heavier-than-air gasses settled somewhere other than the local environment. Regardless how high you make the stack, the NOX, SOX, and CO2 always settles to the ground. That is science, and its repeatable in a lab anywhere on earth.
In a sealed room with no circulation CO2 will eventually settle in the lower part of the room but that takes hours. Outdoors there are almost no weather conditions under which that can happen. But going back to Brewer (1949): http://acmg.seas.harvard.edu/students/Q_J_Roy_Meteor_Soc_1949_Brewer.pdf we can see that CO2 mixes (rises) in the stratosphere with the very slightest bit of turbulence in that stratified layer. In the troposphere the air is mixed enough vertically to cause an even distribution of CO2 (and all other gases) with altitude.
The only exception I can find to that is a very slight decrease of CO2 with altitude, e.g ftp://wxmaps.org/pub/klinger/CLIM690/thoningetal89.pdf of about 2ppm (in summer) over a rise of 13,000 feet.