Christoph Bertram, Elina Brutschin, Laurent Drouet, Gunnar Luderer, Bas van Ruijven, Lara Aleluia Reis, Luiz Bernardo Baptista, Harmen-Sytze de Boer, Ryna Cui, Vassilis Daioglou, Florian Fosse, Dimitris Fragkiadakis, Oliver Fricko, Shinichiro Fujimori, Nate Hultman, Gokul Iyer, Kimon Keramidas, Volker Krey, Elmar Kriegler, Robin D. Lamboll, Rahel Mandaroux, Pedro Rochedo, Joeri Rogelj, Roberto Schaeffer, Diego Silva, Isabela Tagomori, Detlef van Vuuren, Zoi Vrontisi, Keywan Riahi

• Despite faster-than-expected progress in clean energy technology deployment, global annual CO2 emissions have increased from 2020 to 2023. The feasibility of limiting warming to 1.5 °C is therefore questioned. Here we present a model intercomparison study that accounts for emissions trends until 2023 and compares cost-effective scenarios to alternative scenarios with institutional, geophysical and technological feasibility constraints and enablers informed by previous literature. Our results show that the most ambitious mitigation trajectories with updated climate information still manage to limit peak warming to below 1.6 °C (‘low overshoot’) with around 50% likelihood. However, feasibility constraints, especially in the institutional dimension, decrease this maximum likelihood considerably to 5–45%. Accelerated energy demand transformation can reduce costs for staying below 2 °C but have only a limited impact on further increasing the likelihood of limiting warming to 1.6 °C. Our study helps to establish a new benchmark ofDespite faster-than-expected progress in clean energy technology deployment, global annual CO2 emissions have increased from 2020 to 2023. The feasibility of limiting warming to 1.5 °C is therefore questioned. Here we present a model intercomparison study that accounts for emissions trends until 2023 and compares cost-effective scenarios to alternative scenarios with institutional, geophysical and technological feasibility constraints and enablers informed by previous literature. Our results show that the most ambitious mitigation trajectories with updated climate information still manage to limit peak warming to below 1.6 °C (‘low overshoot’) with around 50% likelihood. However, feasibility constraints, especially in the institutional dimension, decrease this maximum likelihood considerably to 5–45%. Accelerated energy demand transformation can reduce costs for staying below 2 °C but have only a limited impact on further increasing the likelihood of limiting warming to 1.6 °C. Our study helps to establish a new benchmark of mitigation scenarios that goes beyond the dominant cost-effective scenario design.…