Tool
How Serious Is an S-Risk?
Severity times probability: compare scenarios of future suffering.
How serious an s-risk is equals how bad the scenario would be multiplied by the probability that it will happen: its expected disvalue. Adjust the values with your own estimates and watch the order of priority change.
The size of each risk
Each square is a scenario: the shaded width is the severity and the height is the probability. The larger the area, the more serious the risk.
Ranking by seriousness
The scenarios are examples from Volume IX; the starting numbers are only illustrative, for you to change. The book's point is the method: even unlikely scenarios can deserve priority if they are gigantic.
Based on Vol. IX, ch. 1: Future Risks for Sentient Beings: An Introduction.