Climate are usually presented as smooth lines rising with emissions.
Several components of the system do not behave that way.
Ice sheets, and some ocean currents have beyond which change continues without further forcing.
Melting lowers the surface of an ice sheet into warmer air, which melts it further.
Once such a is established, stopping emissions does not stop the process.
The uncertainty is not whether these exist but where they sit.
Estimates have moved downward as observation has improved, which is the wrong direction for comfort.
Policy handles this badly because the standard tool is cost-benefit analysis.
That method requires a probability and a price for each outcome.
Neither exists for an event that has no historical and no reversal.
Economists have therefore borrowed the logic of insurance instead.
Nobody insures a house because a fire is likely; they insure it because the loss is unrecoverable.
Framed that way, the argument shifts from the most probable warming to the tail of the .
The tail is where the outcomes sit and where most public debate never goes.
A policy built only around the central estimate is, in insurance terms, an uninsured house.