In our view, Zeke Hausfather and Glen Peters’s recommendation to assign a single set of best-estimate probabilities to all future emissions scenarios as a means to assess climate-change risks (Nature 577, 618–620; 2020) could give decision-makers a false sense of certainty, leading to costly adjustments if the world evolves in unanticipated ways.

The Society for Decision Making Under Deep Uncertainty (www.deepuncertainty.org), to which we belong, offers a better strategy. It relies on methods that focus on the implications of alternative scenarios and the extent to which response tactics are shared across a wide range of scenarios. This helps to manage uncertainties — for example, in sea-level rise after 2050 — by identifying long-term options and short-term, flexible actions that can prepare for a range of future emissions.

Bypassing the need to assign probabilities enables decision-makers to better understand the combination of uncertainties that most affect their choices, thereby reducing locked-in choices and decision delays that can arise when using a single scenario.