Isn't that overly pessimistic, not optimistic?

Surely if plants are absorbing more CO2 than we thought, that's a good thing for climate change? (More CO2 absorbed by plants -> less CO2 staying in the atmosphere -> less warming. No?)

>(More CO2 absorbed by plants -> less CO2 staying in the atmosphere -> less warming. No?)

The vast vast vast majority of co2 absorbed by plants remains in the carbon cycle. The share that leaves it is in fact ridiculously small.

There's absolutely no reasonable scenario where we wait for plants to deal with the output of the fossil fuels pumped up.

Most emitted CO2 also remains in the carbon cycle.

What matters is accumulation at a particular point in the cycle because CO₂ is added to the atmosphere faster than it is removed. If it is removed faster then it ceases to be a problem.

I'm not sure what you're trying to say here. It seems to me the first and last line don't really add anything and I don't see why the middle sentence is necessarily true.

I think the counting errors were "we expected these sinks to fill up slower. They are already full, and not contribute instead of being a sink".

I don't understand this reasoning. How does the presence of a single recent post on HN say anything about if the errors go in one direction or in both directions?

The errors on direct influences to warming have been overwhelming on the "too optimistic" direction. We are above the most pessimistic predictions from decades ago.

The errors on consequences of the warming... I'm not sure one can even talk about them without citing specific studies, because those things tend to have undefined timeframes and way into the future contexts (like this 4°C one... is this even possible to achieve by burning fossil fuels?)