[incrudible]

> This is modulo natural sources and syncs, of course, but CO2's half-life in the atmosphere is long enough that on the immediate timescale those influences can be ignored.

On the immediate time scale, anything can be ignored. Climate change is not about what's going to happen immediately.

Excess CO2 "officially" has a half-life of around 20 years, but this begs the question as to what "excess" actually means. If an increase in CO2 leads to an increase in plant growth and therefore an increased capacity of further uptake down the road, that excess may now in fact be required to maintain plant growth. Those "excess plants" can't wait for all the other plants to decompose and return to the carbon cycle, because that happens on a much longer timescale.

I don't see that this aspect is accounted for in the IPCC models: https://gmd.copernicus.org/articles/11/1887/2018/