Policy solutions to better assess progress toward Paris goals given warming-induced ecosystem emissions, which shorten timelines by 2–5 years

Bioclimatic feedbacks, driven by anthropogenic warming, produce indirectly human-caused emissions that contribute to a significant discrepancy between models, quantification frameworks, and atmospheric change. This discrepancy threatens climate ambitions, but policy is ill equipped to quantify the threat. Under two scenarios (SSP 1-1.9, roughly aligned with Paris Agreement goals and SSP 2-4.5, roughly current trajectory), thawing permafrost, increasing circumboreal fires, and warming tropical wetlands increase CO 2 emissions by ∼15 to ∼300 Tg C year −1 and CH 4 by ∼17 to ∼50 Tg C year −1 above 2020 levels by 2050, lessening time to the 1.5°C and 2.0°C Paris thresholds by ∼21%–25%. Policy frameworks and tools for quantifying/reporting indirect emissions from managed and unmanaged lands should be developed. The Earth system modeling community could inform this effort and would benefit from additional data. Ultimately, increased mitigation ambition to compensate for indirect emissions will likely proceed only if processes are measured and reported.