Rapid warming in South America during the last deglaciation

Understanding tropical land temperature response to rising atmospheric CO₂ in the past is crucial for better constraining future climate projections. However, the evolution of regional land temperatures on paleoclimate timescales remains uncertain due to the paucity of precise records. Here we reconstructed temperatures across the last deglaciation using nucleation-assisted microthermometry in a stalagmite from central-eastern South America. We show that cave temperatures increased by 5.8 ± 0.3 °C (2 standard errors of the mean, SEM) from the Last Glacial Maximum to the early Holocene, broadly tracking global atmospheric CO₂ and Antarctic temperatures. Our results reveal an abrupt regional warming across the Antarctic Cold Reversal-Younger Dryas (ACR-YD) transition, linked to the weakening of the Atlantic Meridional overturning circulation (AMOC). Notably, the most rapid warming at our cave was still slower than projections of future long-term warming, highlighting the unprecedented nature of the current greenhouse gas forcing.