Climate simulations and ice core data highlight the Holocene conundrum over tropical mountains

Resolving discrepancies in long-term Holocene temperature trends between climate models and proxy records is essential to improve future climate projections. However, uncertainties in paleoclimate reconstructions limit their ability to constrain models. This study compares ice core-derived oxygen isotope records with isotope-enabled climate simulations to evaluate model performance and investigate Holocene temperature variability. Our results show that simulated and observed oxygen isotope trends in Greenland and West Antarctica are generally consistent, driven by orbital forcing. However, the model underestimates the early Holocene peak and subsequent decline observed in Greenland records. The most striking mismatch appears in tropical mountains, where the model shows a slight increase in isotopic trends, while proxy records indicate a clear decline. The mechanisms controlling this decreasing isotopic trend remain unclear and cannot be fully explained by temperature or hydroclimate changes alone. Addressing this tropical mountain oxygen isotope conundrum requires efforts to improve the model and paleoclimate interpretations. Analysis of Holocene climate forcing mechanisms suggests a general agreement between ice core oxygen isotope records and climate models in Greenland and West Antarctica. However, contrasting model-data isotopic trends in tropical mountains challenge interpretations and call for further investigation by the paleoclimate community.