Zeke Hausfather and Glen Peters’s discussion of future climate scenarios focuses on what we might expect by 2100 (Nature 577, 618–620; 2020). But why 2100? This inordinate focus on the century’s end, largely derived from Intergovernmental Panel on Climate Change scenarios, has coloured much of the literature for years and now saturates the public debate.

Take, for instance, the authors’ tags for warming above pre-industrial levels: 1.5 °C, “mitigation required to reach Paris goals”; 2.5 °C, “modest mitigation”; 3 °C, “weak mitigation (likely)”; 4 °C, “average no policy (unlikely)”; 5 °C, “worst-case no policy (highly unlikely)”. Peak warming will post-date peak emissions and, depending on feedbacks, the planet will still be warming in 2100 — even in some of the “likely” pathways and certainly in the “unlikely” and “highly unlikely” ones.

Let’s move the discussion to peak impact and a full-recovery timescale, especially when considering policy.