Dr Roy is having a mid life crisis. He writes:
"But what if (I’m NOT necessarily advocating this) most of the CO2 humans produce, which is near the land surface, is absorbed by vegetation, and the observed global increase is partly or mostly due to outgassing of the oceans?"
Most of the CO2 humans produce is created by combustion of fossil fuels.
What part of hot air rises doesn't Dr. Roy understand?
There are more sophisticated answers to this from a whole bunch of atmospheric transport studies