[Question] Climate discounting: How do you value one tonne of CO2eq averted today versus (say) 30 years from now?

Cli­mate dis­count­ing: How do you value one tonne of CO2eq averted to­day ver­sus one tonne of CO2eq averted (say) 10 or 30 or 50 years from now?

Some (po­ten­tially over­lap­ping) fac­tors which should be con­sid­ered:

  • what does warm­ing effect as a func­tion of CO2eq con­cen­tra­tion look like? (pre­sum­ably it’s not lin­ear, i.e. pre­sum­ably the warm­ing effect of an­other tonne when CO2 is 412 ppm is not the same as the marginal effect when CO2 is 500ppm or 1000pm)

  • what does “bad­ness” as a func­tion of warm­ing look like? (again, pre­sum­ably not lin­ear, i.e. I sus­pect that 10 de­grees of warm­ing is prob­a­bly more than 5x worse than 2 de­grees of warm­ing)

  • are there vi­cious cir­cle/​run­away effects?

  • are there cliff-edge effects?

  • how much un­cer­tainty is there in the mod­els? (I un­der­stand the an­swer to be “lots”, in which case should that make us more risk averse, and there­fore more prone to place greater value on im­me­di­ate re­sults)