Two numbers decide most climate arguments, and both are ethical judgements wearing technical costume. Turn the discount rate and watch what a stranger’s future losses are worth to a spreadsheet today. Then switch the accounting basis and watch the list of who owes the most reorder itself — without a single fact about the atmosphere changing.
1 · Turn the dial
Annual discount rate3.0%
0% — future counts fully7%
Damage arrives in100 yrs
10 yrs150 yrs (year 2175)
Anchors used in real analyses
The set-up. One million dollars of damage — a flooded neighbourhood, a lost harvest, a heat-related death toll — lands on people alive in the year shown. The dial says what a regulator today is permitted to call that worth.
3 · Who owes what?
Or set the accounting basis directly
Present value of $1,000,000 of future damage
$0
The ledger
Figures are rounded illustrative shares drawn from the chapter and from standard emissions accounting, used to show how much the ranking depends on the question you ask. Cumulative fossil carbon dioxide since the industrial revolution puts the United States near a quarter of the total and the European Union near a sixth; current annual emissions put China near thirty percent; per person the ordering changes again.