But there is another factor at play which is geographical, other than the mountains. The position of Anarctica, cut off from the other continents, allows it to be a freezer. The southern hemisphere has not warmed as much as the NH. The southern ocean near Antarctica has not warmed at all. Obviousky any warming of Antarctica is a good thing just like the warming of the Arctic. That's because of this simple reason: if the Antarctic sea ice sheild expands far enough north, it will trigger a full glacial period by reflecting the sun.
Our biggest threat is cooling not warming. Now you are correct that CO2 declines with cooling and increases with warming,. But higher CO2 also causes some warming. Not a lot, because if it caused a lot we would have had runaway warming some time in the past billions of years. But the reason we know there's a little warming from CO2 is that with low levels, mainly due to the weathering, we are in a permanent ice age.
Another simple way of looking at CO2 is that about one degree of warming (or cooling) causes about 5 or 10 ppm of increase (or decrease) in CO2. We have had 130 ppm rise of CO2 caused in the recent past by fossil fuel burning, etc. not by warming. Now the pertinent question is how much warming has that increase in CO2 caused. The answer: not much.
And not enough to make one iota of difference in plant growth. If it were greenhouses wouldn't pump it up to 1,000 ppm.
We have had 130 ppm rise of CO2 caused in the recent past by fossil fuel burning, etc. not by warming.
That's just a guess not a fact.