Permafrost carbon–climate feedback amplifies Earth system tipping risks

Global warming leads to widespread permafrost thaw and subsequent emissions of carbon dioxide and methane, driving the permafrost carbon–climate feedback (PCF) which amplifies climate change. Many current-generation climate models omit this feedback, limiting projections of long-term temperature outcomes and associated Earth system tipping risks. Here, we investigate how this feedback affects the risk and timing of crossing tipping points in the Earth system by integrating permafrost carbon emissions into temperature projections for idealized stabilization and overshoot scenarios. In a conceptual network model of interacting climate tipping elements—including the Greenland and West Antarctic ice sheets, the Atlantic Meridional Overturning Circulation, and the Amazon rainforest, we find that PCF leads to additional warming that increases the probability of exceeding one or more tipping elements by up to 50% and can substantially accelerate the timing of tipping events by hundreds of years. The effect of PCF on tipping risk and acceleration is particularly evident in overshoot scenarios with lower peak temperatures below 2–3 C or peak cumulative emissions of below 2000 PgC. Considering PCF, therefore, narrows the critical temperature space for overshoot pathways. Our results highlight that failing to account for PCF underestimates both climate risks and the urgency of mitigation, increasing the likelihood of tipping events across the Earth system.