It's the average temperature at which trees start to die, not the average temperature over a year. Just a couple of weeks at that temp will do a lot of damage.

It's the average temperature at which trees start to die, not the average temperature over a year. Just a couple of weeks at that temp will do a lot of damage. The point is that ~2C or so from the pre-warming baseline you start seeing signs of a mass die off. And ~4C or so the damage starts to become systemic and irreversible.