We invite contributions on palaeoclimate-specific model development, tuning, simulations, and model-data comparison studies. Simulations may be targeted to address specific questions or follow specified protocols (as in the Paleoclimate Modelling Intercomparison Project – PMIP or the Deep Time Model Intercomparison Project – DeepMIP). They may include or juxtapose time-slice equilibrium experiments and long transient climate simulations (such as over the last millennium). Comparisons may include different time periods (e.g., deep time, Quaternary, historical as well as future simulations), and focus on comparison of mean states, spatial gradients, circulation or modes of variability using different models, or contrast model results with reconstructions of temperature, precipitation, vegetation or circulation tracers (e.g. δ18O, δD or Pa/Th).
Presentation and discussion of results using CMIP7 models and experiments that from part of PMIP7 are particularly encouraged. However, we also solicit comparisons across time periods, between models and data, and analyses of underlying mechanisms of change as well as contributions introducing novel model or experimental designs that allow to improve future projections.
The mechanisms governing the initiation and subsequent growth of Northern Hemisphere ice sheets during the last glacial inception remain incompletely understood, in particular, the transition from single, scattered ice nuclei to developed, large-scale ice sheets. Here we present fully coupled climate–ice sheet simulations spanning 127–65 ka BP, performed with the Earth system AWI-ESM. To make the long transient simulations computationally feasible, orbital and greenhouse gas forcing are accelerated by a factor of 20. A bias correction is applied for monthly near-surface air temperatures over North America.
The simulation produces extensive North American ice sheets, with initial ice-sheet development beginning around 120 ka over Baffin Island and the Quebec region. Rates of ice-sheet growth closely follow variations in boreal summer insolation at 65°N, reflecting the dominant role of the precession cycle during early glacial inception. During this phase, ice-sheet nucleation and early expansion are primarily controlled by reductions in summer near-surface air temperature, allowing persistent snow cover and positive snow–albedo feedbacks. At later stages, once a continental-scale ice sheet is established, a self-sustaining feedback emerges. The presence of the ice sheet enhances precipitation along its southern and southwestern margins, promoting further ice advance into lower latitudes and reinforcing ice-sheet growth.
Our results suggest a two-phase glacial inception: an insolation-driven initiation phase followed by a dynamically maintained growth phase governed by ice-atmosphere feedbacks. These findings provide new insights into the processes involved in the last glacial inception and highlight the importance of fully coupled climate–ice-sheet models.
How to cite: Ackermann, L., Knorr, G., and Lohmann, G.: Fully coupled climate–ice sheet simulation of North American ice-sheet evolution during the last glacial inception, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9567, https://doi.org/10.5194/egusphere-egu26-9567, 2026.
Modelling rapid climate perturbations in past warm climates of the geological record provides a powerful test for climate models under boundary conditions far outside the historical range. Eocene hyperthermal events are short-lived episodes of rapid greenhouse gas release, and represent the fastest large-scale carbon perturbations in the paleoclimate record. However, the mechanisms governing their onset, magnitude, and recovery remain partially understood due to limitations in proxy data coverage and resolution. Long transient simulations with fully coupled climate models are therefore essential to bridge this gap and to evaluate model behaviour under extreme climate forcing. Here, we present a novel low-resolution paleoclimate configuration (TL63L31–PALEORCA2; ~2.8° atmospheric and ~2° oceanic resolution) of the EC-Earth4 Earth System Model, developed to investigate past warm climate states. This configuration achieves a computational performance of ~230 simulated years per day using 256 MPI cores on the ECMWF ATOS HPC2020 system, enabling computationally efficient multi-century to multi-millennial simulations with a fully coupled atmosphere–ocean climate model. We apply this configuration to the DeepMIP protocol for the Paleocene–Eocene Thermal Maximum (PETM) to investigate Eocene climate dynamics, focusing on (1) atmospheric and oceanic circulation, (2) the hydrological cycle, and (3) regional and global climate extremes. We assess model proxy mismatches and evaluate the EC-Earth4 integrations in comparison with other DeepMIP integrations. The new configuration also establishes a shared modelling framework that can support paleoclimate research and collaborative model development within the European climate modelling community.
How to cite: Coppo, R., Sozza, A., Nurisso, M., Meccia, V., Fabiano, F., and Davini, P.: Unlocking Multi-Millennial Eocene Simulations with a New EC-Earth4 Configuration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10249, https://doi.org/10.5194/egusphere-egu26-10249, 2026.
The Penultimate Deglaciation (PDG, ~ 136-129 ka) saw warming from the Penultimate Glacial Maximum to the Last Interglacial (LIG), which was likely the most recent time Earth was as hot as today. The PDG may have seen a different pattern of AMOC behaviour compared to the more widely-studied Last Deglaciation. Using a low-resolution Earth System model with 3-D dynamic atmosphere and oceans and interactive sea-ice and vegetation, we run 18,000-year-long transient, perturbed parameter ensemble simulations varying 31 model parameters. Simulations span the entire PDG and the early LIG. AMOC can display either one, two or three phases of weakening and recovery, dependent on meltwater forcing uncertainty and parametric uncertainty. Surprisingly, vegetation parameters are shown to have a strong influence on PDG AMOC behaviour, including whether or not a brief interstadial occurs in the late stage of the PDG around 131 ka. The early AMOC stadial drives a reduction in Northern Hemisphere vegetation cover, particularly in Eurasia, which causes a multi-millennial cooling persisting beyond the termination of meltwater forcing. The ensemble spread of LIG global temperature is also strongly linked to vegetation parameters, and a stronger 131 ka AMOC interstadial is associated with a cooler (less realistic) LIG.
How to cite: Cutler, T., Holden, P., Edwards, N., and Anand, P.: Vegetation parameters control AMOC interstadials in Penultimate Deglaciation perturbed parameter ensemble simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14200, https://doi.org/10.5194/egusphere-egu26-14200, 2026.
This study employs the iTraCE transient simulation results over the past 21,000 years as lateral boundary conditions, nested within the RegCM4.7 regional climate model, to perform high-resolution simulations of millennial-scale climate variations in the China region since the Last Glacial Maximum (LGM). The findings indicate that the RegCM model significantly ameliorates the temperature and precipitation biases associated with the coarse resolution of iTraCE, thereby providing a more accurate representation of regional climate dynamics during the observational period. Comparative analyses of temperature and precipitation trends across various periods since the LGM show that both the iTraCE and RegCM simulations successfully reproduce the climatic features of the LGM, characterized by a dry and cold climate, as well as the Holocene, which is characterized by a warm and wet climate, as reconstructed from proxy data. By contrasting the reconstructed records with the simulation outputs for four distinct regions of China—northern China, southern China, the Tibetan Plateau, and the northwest—this study explores the contribution of seasonal temperature variations to the discrepancies in the trends of Holocene mean annual temperature changes between the reconstructed records and simulations. In northern China, the Tibetan Plateau, and the northwest, the simulations suggest that mid-Holocene temperatures were higher than those in the late Holocene, although winter temperatures during the mid-Holocene were lower than those in the late Holocene, with a more pronounced seasonal temperature variation. In contrast, in southern China, the simulated mid-Holocene summer and winter temperatures were lower than those of the late Holocene, leading to differences in the trends of simulated and reconstructed mean annual temperatures. Notably, the reconstructed summer temperature changes were found to be in good agreement with the simulated summer temperature variations in northern and northwest China.
How to cite: Cao, N., Ning, L., Liu, J., Liu, Z., Yan, M., Sun, W., Jiang, M., Kuang, X., Lu, H., Chen, K., Qin, Y., Wen, Q., and Xing, F.: Downscaling Simulation Study of Regional Climate in China Since the Last Glacial Maximum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2184, https://doi.org/10.5194/egusphere-egu26-2184, 2026.
Marine Isotope Stage 3 (MIS 3) is characterised by millennial-scale climate transitions, including Dansgaard–Oeschger events recorded in Greenland oxygen isotope ice cores and Heinrich events identified in marine sediment records. These changes are associated with variations in the Atlantic Meridional Overturning Circulation and are influenced by atmospheric circulation, with pronounced impacts on the regional paleoclimate in Europe.
Here we assess the changes in large-scale atmospheric circulation and regional climate during MIS 3, with a focus on the Iberian Peninsula. A freshwater hosing experiment was carried out using the global Earth system model NorESM1-F under boundary conditions representative of Greenland Interstadial 8 (GI-8; 38 kyr BP), capturing the transition from Heinrich Event 4 (H4) to GI-8. Dynamical downscaling was then performed for the Iberian Peninsula using the regional climate model WRF at 9 km horizontal resolution, forced by NorESM1-F output, to simulate regional circulation and associated temperature and precipitation patterns.
Preliminary results from the downscaled simulations suggest clear stadial–interstadial contrasts over Iberia, including a shift toward wetter winters and drier summers during cold stadials. These regional signals appear consistent with NorESM1-F–simulated changes in North Atlantic circulation, including shifts in the position and strength of the westerly jet and associated moisture transport during H4. This study offers an enhanced assessment of the regional climate in the Iberian Peninsula during MIS 3 by linking large-scale atmospheric dynamics with regional circulation and precipitation patterns.
How to cite: Ozdogru, I. N., Guo, C., Göktürk, O. M., Nisancioglu, K. H., and Cascalheira, J.: The Impact of the Heinrich Stadial–Greenland Interstadial Transition during Marine Isotope Stage 3 on Large-Scale Atmospheric Circulation over Western Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13009, https://doi.org/10.5194/egusphere-egu26-13009, 2026.
The Greening of the Sahara (GS) during the African Humid Period (AHP) is a striking example of past climate–vegetation interactions, yet its detailed spatiotemporal patterns across the Holocene remain insufficiently understood. This study develops a data-driven framework that combines paleoclimate simulations with machine learning to reconstruct vegetation dynamics in North Africa. Two machine learning models—an artificial neural network (ANN) and a random forest (RF)—were trained on observed nonlinear relationships between vegetation and climate variables. These models were applied to paleoclimate proxy data and the transient climate simulation TraCE-21ka to estimate Holocene normalized difference vegetation index (NDVI). The ANN model outperformed RF in representing complex vegetation–climate linkages and showed closer agreement with proxy evidence. ANN-based reconstructions indicate a rapid expansion of vegetation in North Africa and the Arabian Peninsula following the Younger Dryas (~12,000 years BP), sustained high vegetation cover during the AHP (10,000–6,200 years BP), and a gradual decline thereafter. However, the ANN underestimated both the overall vegetation cover and the abrupt decline around 6,000 years BP suggested by proxy data. Sensitivity analyses highlight monsoon-driven precipitation as the primary control on vegetation change, with temperature exerting a secondary but reinforcing influence. This machine learning–based framework provides a new perspective for investigating vegetation responses to past and future climate change.
How to cite: Hao, G., Sun, W., Liu, J., Chen, D., Ning, L., Shen, C., Lu, B., Zhang, X., and Lv, G.: Holocene Evolution of Saharan Vegetation Revealed by Paleoclimate Simulations and Machine Learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1967, https://doi.org/10.5194/egusphere-egu26-1967, 2026.
The Miocene epoch, marked by significant tectonic and climatic shifts, presents a unique period to study the evolution of South Asian summer monsoon (SASM) dynamics. Previous studies have shown conflicting evidence: wind proxies from the western Arabian Sea suggest a weaker Somali Jet during the Middle Miocene compared to the Late Miocene, while rain-related records indicate increased SASM rainfall. This apparent decoupling of monsoonal winds and rainfall has challenged our understanding of SASM variability. Here, using the fully coupled EC-Earth3 model, we identify a key driver of this decoupling: changes in African topography rather than other external forcings such as CO2 change. Our simulations reveal that changes in Miocene African topography weakened the cross-equatorial Somali Jet and reduced upwelling in the western Arabian Sea, while simultaneously enhancing monsoonal rainfall by inducing atmospheric circulation anomalies over the Arabian Sea. The weakened Somali Jet fostered a positive Indian Ocean Dipole-like warming pattern, further amplifying the monsoonal rainfall through ocean-atmosphere feedbacks. In contrast, CO2 forcing enhances both Somali Jet and rainfall simultaneously, showing no decoupling effect. These findings reconcile the discrepancies between wind and rainfall proxies and highlight the critical role of African topography in shaping the multi-stage evolution of the SASM system.
How to cite: Han, Z., Werner, N., Wang, Z., Li, X., Yao, Z., and Zhang, Q.: Miocene African topography induces decoupling of Somali Jet and South Asian summer monsoon rainfall, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7214, https://doi.org/10.5194/egusphere-egu26-7214, 2026.
While anthropogenic warming is projected to green the Sahara region, the potential impacts on tropical cyclone (TC) activity remain poorly understood. Here we examine the mid-Holocene (MH; ~6 ka BP) Sahara greening (characterized by expanded vegetation and substantially reduced dust emissions) as a potential analog for the future, combining high-resolution global atmospheric model simulations with paleoclimate proxy records. The simulation results demonstrate that Sahara greening dramatically reduced North Atlantic (NA) TC frequency to near-zero levels while causing minimal changes in other basins. In simulations without Sahara greening, the MH TC distribution resembles the pre-industrial pattern, albeit with an eastward shift of TC genesis in the North Pacific. The greening-induced TC suppression primarily resulted from two mechanisms: (1) enhanced vertical wind shear off West Africa and (2) reduced low-level moisture over the western tropical NA. These findings align well with reconstructed NA TC variability and may provide important insights into future TC activity under potential Sahara greening scenarios.
How to cite: Ou, Y., Zhang, M., Liu, Y., Zhao, H., Cao, X., and Zhu, J.: Green Sahara may have Diminished Atlantic Tropical Cyclones: Insights from the Mid-Holocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10533, https://doi.org/10.5194/egusphere-egu26-10533, 2026.
The Pliocene is thought to have been warmer than present-day and has been the focus of many studies as a possible analogue of near-future warming. In the Pliocene, there were less tundra and more forests in the Arctic, the Sahara Desert was smaller than in present-day, and there were more grassland and forests elsewhere. Studies with multiple climate models in PlioMIP2 have indicated that, factors other than atmospheric CO2, such as paleogeography, vegetation, and ice sheets, also play an important role in shaping the Pliocene climate. In many modelling studies, vegetation, which can change in response to the other forcings, is fixed. In this study, in order to investigate the role of CO2 and paleogeography including the effect of vegetation feedback, we conducted experiments using an atmosphere-ocean-vegetation coupled model, MIROC4m-AOV. We set CO2 concentration and paleogeography to those of pre-industrial and of the Pliocene as prescribed by the PlioMIP3 protocol. We also conducted experiments in which conditions at northern and southern high latitudes are set to Pliocene separately. While Pliocene CO2 concentration contributes to a globally warmer climate than pre-industrial, paleogeography has a large effect, both seasonally and locally. With Pliocene paleogeography, the continents at northern high latitudes tend to be warmer in summer and colder in winter. The summer warming in these regions causes a reduction in tundra and an increase in forests, further enhancing the warming. The Pliocene paleogeography of the northern high latitudes also enhances the precipitation in North Africa via the summer monsoon.
How to cite: Nakagawa, S., Abe-Ouchi, A., Chan, W.-L., O'ishi, R., and Higuchi, T.: Investigating the roles of CO2 and paleogeography in shaping the Pliocene climate using an atmosphere-ocean-vegetation coupled model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10200, https://doi.org/10.5194/egusphere-egu26-10200, 2026.
How to cite: Naik, T., de Boer, A., Coxall, H., Burls, N., Bradshaw, C., Donnadieu, Y., Farnsworth, A., Frigola, A., Herold, N., Huber, M., Karami, M. P., Knorr, G., LeGrande, A., Li, Y., Lohmann, G., Lunt, D., Prange, M., and Zhang, Y.: Large-Scale Ocean Circulation During the Early and Middle Miocene: Insights from MioMIP1 Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10949, https://doi.org/10.5194/egusphere-egu26-10949, 2026.
The Atacama is the driest warm desert on the planet yet the geological evidence indicate it was far more humid in the past. Factors such as Humboldt ocean current and orogenic effect of the Andes are said to contribute to it's extreme aridity today. How these factors and their influence on the hydroclimate of Atacama changed over geological time remains poorly understood.
As part of the CRC1211 project - Earth,Evolution at dry limits - we investigate the key drivers of Atacama hydroclimate and the mechanisms of land–ocean coupling that shape them using the stable-water-isotope-enabled AWI Earth System Model (AWI-ESM-wiso). The set up consists of coupled Atmosphere (ECHAM) and ocean(FESOM) models with Water ISOtope (WISO) model which simulates absolute concentrations of H$_2$$^{16}$O, H$_2$$^{18}$O, and D$_2$$^{16}$O in the atmosphere, ocean and ice.
We examine climate conditions across four time periods: the Miocene, the Last Glacial Maximum, the Last Interglacial, and the Mid-Holocene. We investigate how the Humbolt current have changed during this time to understand its effect on precipitation over Atacama. Our results reveal distinct shifts in moisture-transport pathways and moisture sources to the Atacama throughout the time intervals. To assess model performance, we compare simulated δ¹⁸O values with measured δ¹⁸O from foraminifera.
How to cite: Prasannakumar, A., Werner, M., Grunert, P., Samal, S., Sun, Y., and Knorr, G.: Past Climates of Atacama Desert, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-795, https://doi.org/10.5194/egusphere-egu26-795, 2026.
Tropical Cyclones are a dominant feature of the summertime climate over northern Australia. Their passage onto the continent brings severe winds, heavy precipitation and storm surges that have significant impacts on inhabitants lying in their path. Tropical Cyclones that impact Australia form in three genesis regions, the Coral Sea to the north-east of Australia, the western Gulf of Carpentaria, and off the north-west coast of Australia. The present-day climate of Australia experiences up to 20 Tropical Cyclones per year, with an average of 5 of these classified as severe.
The present-day climate of Tropical Cyclones impacting Australia has been widely studied. There has, however, never been analysis of Tropical Cyclones for the palaeoclimate of Australia using down-scaled climate models. Here we present the first analysis of Tropical Cyclones from such modelling. The results presented are from three time slice simulations: mid-Holocene (6 ka), the late Pleistocene (12 ka), and the Last Glacial Maximum (21 ka), compared to a pre-industrial control simulation (1850 CE). The simulations were performed with the Weather Research and Forecasting (WRF) model, downscaled from boundary and initial conditions taken from the Community Earth System Model (CESM).
How to cite: Lowry, A. and McGowan, H.: Quantifying Tropical Cyclones impacting Australia in the late Quaternary using downscaled models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7008, https://doi.org/10.5194/egusphere-egu26-7008, 2026.
East Asia (EA) has experienced a decreasing trend in the summer-to-winter temperature difference (temperature seasonality) in the context of ongoing global warming. However, the impacts of natural external forcing remain unclear. The last deglaciation, marked by substantial global warming, provides a paleoclimate context for understanding the roles of natural forcing in EA temperature seasonality changes. Here, using transient simulations (iTraCE), we demonstrate that EA experienced greater winter warming compared to summer during the last deglaciation, supported by paleo-climatic reconstructions. Sensitivity experiments indicate that the inundation of continental shelf area due to rising sea-level played a critical role in driving these differential warming trends. Further quantifications highlight the contributions of greater heat capacity instead of reduced surface albedo of the expanded ocean area. Resulting atmospheric responses expanded the seasonality change to EA landmass by cloud‒radiation feedback and temperature advection processes. These findings provide insight into the potential climatic impacts of sea-level rise under ongoing global warming.
How to cite: Ma, Y., Sun, W., Liu, J., Ning, L., Chen, D., Zhao, K., Meng, X., Yan, M., and Lu, H.: Continental shelf area inundation drove reduced temperature seasonality in East Asia during the last deglaciation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3930, https://doi.org/10.5194/egusphere-egu26-3930, 2026.
Anthropogenic climate change threatens to push many Earth system components towards uncharted territory, including the ocean circulation and marine ecosystems, which may substantially impact the oceans capacity to take up additional CO2 in the future. Paleoceanographic reconstructions offer critical insights into how these systems respond to past abrupt and long-term climate changes. Yet, their interpretation often remains challenging and uncertain due to the inherent local signal of marine sediment cores as well as confounding factors from other environmental variables. Proxy-enabled Earth system models have emerged as essential tools to address these challenges. Here we present initial results from a new nitrogen isotope implementation in the Bern3D Earth system model of intermediate complexity. Nitrogen isotopes are sensitive indicators of the oceanic fixed nitrogen inventory, which regulates the strength of the biological pump, and are increasingly reconstructed from marine sediments. In the Bern3D model, they are complemented by a wide array of already implemented proxies for ocean circulation and marine biogeochemistry, which further strengthens the robustness of this approach. New reconstructions and data compilations of a range of proxies, including N-isotopes, are generated within the Past-To-Future Horizon Europe project and will be crucial to constrain the model’s biogeochemical response to past climate change, here investigated for snapshot and transient simulations.
How to cite: Millet, B. and Pöppelmeier, F.: Novel implementation of nitrogen isotopes in the Bern3D model to constrain its past utilization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4869, https://doi.org/10.5194/egusphere-egu26-4869, 2026.
The 4.2 ka BP event (approximately 4200~3900 years before present) was a widespread episode of global drought and cooling during the middle-late Holocene, which has attracted significant attention due to the temporal coincidence with the evolution and sociocultural transformations of early human civilizations in the Indus Valley, the Yellow River basin, and Mesopotamia, among other regions. However, the global consistency and the climate change mechanisms of the 4.2 ka BP event remain debated, particularly regarding the spatial hydroclimatic patterns and principal driving factors within the East Asian monsoon region. Here we conducted a set of transient simulations for the middle-late Holocene (6~3 ka BP) using the Community Earth System Model version 1.0.4 (CESM1.0.4), incorporating orbital parameters (precession, eccentricity, and obliquity), greenhouse gases (CO₂, CH₄, and N₂O), and solar irradiance as external forcings. The Weather Research and Forecasting (WRF) model was employed for dynamical downscaling to produce a high-resolution (~40 km) dataset over the East Asian monsoon domain. These data are synthesised to reveal the spatial modes of temperature and precipitation in the East Asian monsoon region and their connection to global ocean-atmosphere system variations during the 4.2 ka BP event.
Preliminary results indicate that: (1) multicentennial variations in the Atlantic Meridional Overturning Circulation (AMOC) likely dominated winter-half year (October to March) and summer (July to September) precipitation anomalies in North China during 4.2~3.9 ka BP; and (2) multicentennial variations in AMOC and the Pacific Decadal Oscillation (PDO) may be linked to shifts between “north-dry/south-wet” and “north-wet/south-dry” rainfall patterns over East Asia. The underlying mechanisms, however, require further investigation. This study aims to advance the understanding of abrupt climate change events and to provide a scientific basis for examining the relationship between climatic variability and the development of human civilizations.
How to cite: Wang, Y. and Yang, H.: Transient Simulation and Dynamics of the 4.2 ka BP Event in the East Asian Monsoon Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9408, https://doi.org/10.5194/egusphere-egu26-9408, 2026.
Paleoclimates provide examples of past climate change that inform estimates of modern warming from greenhouse-gas emissions, known as Earth's climate sensitivity. However, differences between past and present climate change must be accounted for when inferring climate sensitivity from paleoclimate evidence. The closest paleoclimate analog to near-term warming from greenhouse-gas emissions is the Pliocene (5.3-2.6 Ma), a warm epoch with atmospheric CO2 concentrations similar to today. Recent reconstructions indicate the Pliocene was 1°C warmer than previously thought, implying higher climate sensitivity, which is also supported by recent reconstructions showing more cooling with reduced CO2 at the Last Glacial Maximum (LGM; 19-23 thousand years ago).
However, large-scale patterns of paleoclimate temperature change differ strongly from modern projections under CO2 forcing. Climate feedbacks and sensitivity depend on temperature patterns, and such "pattern effects" must be accounted for when using paleoclimates to constrain modern climate sensitivity.
Here we combine data-assimilation reconstructions with atmospheric general circulation models to show Earth's climate is more sensitive to Pliocene and LGM forcing than modern CO2 forcing. Pliocene ice sheets, topography, and vegetation alter patterns of ocean warming and excite destabilizing cloud feedbacks, and LGM feedbacks are similarly amplified by massive ice sheets. Accounting for paleoclimate pattern effects produces a best estimate (median) for modern climate sensitivity of 2.8°C and 66% confidence interval of 2.4-3.4°C (90% CI: 2.1-4.0°C), substantially revising climate sensitivity's upper bound and projections of 21st-century warming.
How to cite: Cooper, V., Armour, K., Hakim, G., Tierney, J., Burls, N., Proistosescu, C., Andrews, T., Dong, W., Dvorak, M., Feng, R., Osman, M., and Dong, Y.: Paleoclimate Pattern Effects in the Pliocene and Last Glacial Maximum Help Constrain Modern Climate Sensitivity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13141, https://doi.org/10.5194/egusphere-egu26-13141, 2026.
In order to reconstruct long-term global climate variability, climate simulations using Global Climate Models (GCMs) are essential. However, long-term GCM simulations that incorporate complex physical processes require substantial computational resources, often prompting studies to adopt a time-slice simulation approach or use GCMs with intermediate complexity. To address issues arising from limited computational resources, statistical climate emulators constructed from GCM ensemble simulations have been proposed as a mean of quickly producing GCM’s climate responses to any changes in input parameters that were not explicitly simulated by the GCM. In this study, we built a Gaussian Process (GP)–based emulator to approximate key climate variables simulated by the intermediate-complexity climate model LOVECLIM, including surface air temperature, precipitation, surface pressure and zonal and meridional winds. Following future the CO2 emission scenarios employed by Lord et al., we constructed 80 LOVECLIM ensemble equilibrium climate simulations covering both the near-future high-CO₂ state and the long-term low-CO₂ state. Each simulation was distinguished by four external forcing variables (ecosω, esinω, ε and CO2). Multivariate (five climate variables) principal component analysis (PCA) was applied to extract the principal components (PCs) of inter-ensemble variability. GP emulations were conducted using the leading five PCs, thereby setting up a GP-PCA-based emulator. The performance of this emulator was evaluated using Leave-One-Out Cross Validation (LOOCV). Comparisons with LOVECLIM simulations revealed stable overall predictive performance, as indicated by scatter plots and RMSE values. Reconstructed climate time series over the past one million years exhibit differences in scale and variability specific to each variable, leading to variations in the magnitude and representation of prediction errors. Nevertheless, the multivariate emulator consistently reproduces the evolution of the climate time series over the past one million years, as well as the corresponding global spatial patterns. Its evaluation through comparisons with regional sea surface temperature (SST) proxy records. Future projections exhibited scenario-dependent differences in the early stages, followed by gradual convergence across CO₂ scenarios. Future work will extend to the ensemble emulator by incorporating additional GCMs, such as CESM, and will compare their predictive performance.
How to cite: Lee, C.-Y., Kim, J.-H., and Jun, S.-Y.: Long-Term Climate Reconstruction Using a Statistical Emulator Based on Gaussian Process and Multivariate Principal Component Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15885, https://doi.org/10.5194/egusphere-egu26-15885, 2026.
Seasonal hydroclimate variability governs water availability, agricultural productivity, and societal resilience across monsoon Asia, yet its response to abrupt climatic extremes remains poorly constrained. Here we present seasonal-resolution δ18O and trace-element data from an annually laminated stalagmite in northern China, providing a direct reconstruction of East Asian summer monsoon (EASM) seasonality across the 2.8 ka extreme event. The records reveal rapid (<10 yr) transitions into multi-decadal weakened-monsoon states, marked by delayed onset and shortened midsummer rainfall stage, together with a shift from “W-shaped’’ to “V-shaped” δ18O seasonal cycle at the northern margin of the EASM domain. Our experiments with an isotope-enabled simulations show that North Atlantic cooling associated with weakened overturning circulation suppressed the Arabian Sea convection, displacing the westerly jet southward, shortening the core monsoon rainfall stage, and imparting northwestern westerly-dominated δ18O seasonality to the monsoon fringe. Comparison with contemporaneous historical and archaeological evidence indicates that the intensification of hydroclimate seasonality during dry-wet transitions may have imposed the decisive climatic stress precipitating the Shang dynasty’s decline. These results highlight altered monsoon seasonality, rather than mean aridity alone, as a critical dimension of past climate extremes and a key determinant of societal vulnerability.
How to cite: Lin, F., Tan, L., and Liu, Z.: Rapid reorganization of monsoon seasonality during the 2.8 ka event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16033, https://doi.org/10.5194/egusphere-egu26-16033, 2026.
The Last Glacial Maximum (LGM, ~21 ka BP) is a key period for assessing climate sensitivity and evaluating Global Circulation Models (GCMs) used for future climate projections. However, determining whether regional cooling reflects a uniform decrease in monthly temperatures throughout the year (i.e., no change in seasonality) or a change in seasonality, would have significant implications for many paleotemperature reconstructions, including those based on paleo-glacier equilibrium lines.
In this study, we provide assessment of European climate seasonality during the LGM, using both GCMs and sensitivity experiments performed with the Earth system model of intermediate complexity iLOVECLIM downscaled over Europe. Models generally show a large dispersion in the pattern of differences between summer and winter, although some common features seem to emerge. Southern Europe shows a reduction in average seasonality during the LGM, in contrast to an amplification further north, relative to PI condition. Near coastal regions (low longitudes), models indicate a slight and consistent increase in seasonal anomalies, whereas eastern Europe shows a larger increase in seasonal anomalies, though with greater inter-model variability. We identify variations in LGM MTCO (the winter temperatures) as the primary drivers of both seasonality changes and inter-model discrepancies in both the GCM and iLOVECLIM outputs, with the largest disagreements occurring in northeastern Europe, over and near the Fennoscandian ice sheet.
Motivated by the fact that the iLOVECLIM model produces some features largely different from the GCM mean, we performed a series of sensitivity experiments. These include changes in greenhouse gas concentration, thermohaline circulation, albedo and topography of the Fennoscandian ice sheet and vegetation cover. We show that none of these processes reduces the mismatch between iLOVECLIM and the mean response of the GCMs. A significant reduction of this mismatch is achieved only by changing the vertical parametrisation in iLOVECLIM, suggesting that the lack of an explicit vertical representation in iLOVECLIM might bias the simulated seasonality changes at the LGM relative to PI.
Pollen-based reconstructions are generally consistent with model results. However, the regions that display the largest inter-model differences are also not covered by this type of data. European seasonality changes since the LGM therefore remain a key yet poorly constrained characteristic of LGM climates, calling for more single-model sensitivity experiments to improve our understanding of past and future seasonality changes.
How to cite: Fénisse, G., Quiquet, A., Blard, P.-H., and Bekaert, D. V.: European seasonal temperature changes since the Last Glacial Maximum: Insights from model simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18642, https://doi.org/10.5194/egusphere-egu26-18642, 2026.
The tectonic transition from the open to closed CAS during the mid-Miocene to mid-Pliocene (~16-3 Ma BP) is often thought of as a key factor for the development of the tropical Pacific oxygen minimum zone. In this study we investigate the impact of an open Central American Seaway (CAS) on the equatorial current system and oxygen minimum zone in the tropical Pacific. We compare simulations with two independent global climate models (Kiel Climate Model and HadCM3) where the sill depth of the open CAS was set to the same different levels, ranging from shallow to deep.
Both models show a substantial increase in oxygen concentrations in the subsurface eastern tropical Pacific waters in response to the open CAS. Detailed multi-model analysis reveals that the CAS opening results in two main oxygen anomalies in the eastern Pacific, one located below the surface (more northward) and another in deeper (more equatorward) water masses.
Estimates of the water mass transport from west to east driven by the equatorial undercurrent (EUC), the north equatorial counter current (NECC) and the northern subsurface counter current (NSCC) agree well between both models for preindustrial (closed CAS) as well as for the open CAS experiments. Both models show that the open CAS is associated with an enhanced eastward subsurface NSCC in the northeastern tropical Pacific that transports oxygen-rich waters from the western tropical Pacific toward the eastern equatorial Pacific. This mechanism can explain the simulated deeper (and more equatorward) oxygen enrichment in the eastern equatorial Pacific. Potential factors responsible for the more northern anomaly are also analysed.
How to cite: Khon, V., Hoogakker, B., Schneider, B., Segschneider, J., Park, W., Tindall, J., and Haywood, A.: Impact of an open Central American Seaway on the Pacific oxygen minimum zone from simulations with global climate models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21261, https://doi.org/10.5194/egusphere-egu26-21261, 2026.
Past ocean temperatures are widely used to constrain Earth System Models under climate states that differ substantially from the historical period, like the Last Glacial Maximum (LGM). However, the reliability of model–data comparisons critically depends on the robustness of the temperature proxies and on our ability to correctly interpret the signals they record. The alkenone-based UK’37 index is among the most widely applied proxies for reconstructing past sea surface temperatures (SST), but significant deviations persist at both low and high temperatures of the modern calibration. These biases highlight unresolved uncertainties in the environmental and biological controls on alkenone production, as most UK’37 calibrations implicitly assume that coccolithophores record surface temperature uniformly and continuously, neglecting ecological variability in depth habitat and seasonality.
Here, we present a revised calibration approach that explicitly incorporates the spatiotemporal ecology of alkenone-producing coccolithophores. We combine new global biomass estimates derived from a machine-learning reconstruction(a) based on the CASCADE dataset(b) with simple growth relationships(c) to estimate coccolithophore net primary productivity. These depth- and season-resolved coccolithophores productivity estimates are then used to weight the global temperature field.
Our results indicate that accounting for the impact of coccolithophore ecology on the UK’37 signal leads to systematically warmer reconstructed temperatures in cold regions and cooler ones in warm regions relative to classical SST-based calibrations. This produces a slightly reduced calibration slope relative to previous field calibrations, although in good agreement with culture work, and a pronounced latitudinal structure in bias relative to mean annual SST. Applying the same framework to the analysis of the IPSL-CM5A2 present and LGM climate simulations (which explicitly represents the nano-phytoplankton group using the PISCES module), demonstrates that these biological biases vary across climate states and that using our revised calibration reduces model-data mismatches. Overall, this approach highlights the value of coupling biogeochemical information with climate simulations to improve proxies interpretation and strengthen the paleoclimate constraints imposed on climate models.
(a). de Vries, J., Poulton, A. J., Young, J. R., Monteiro, F. M., Sheward, R. M., Johnson, R., Hagino, K., Ziveri, P., and Wolf, L. J.: CASCADE: Dataset of extant coccolithophore size, carbon content and global distribution, Scientific Data, 11, 920, https://doi.org/10.1038/s41597-024-03724-z, 2024.
(b). de Vries, J., Monteiro, F. M., Poulton, A. J., Wiseman, N. A., and Wolf, L. J.: A diverse community constitutes global coccolithophore calcium carbonate stocks, in review, 2025.
(c). Hopkins, J. and Balch, W. M.: A New Approach to Estimating Coccolithophore Calcification Rates from Space, Journal of Geophysical Research, 123, 1447–1459, https://doi.org/10.1002/2017JG004235, 2018.
How to cite: Bauer, V., Gray, W. R., de Vries, J., and Kageyama, M.: Accounting for habitat-depth and seasonality effects on the UK′37 temperature proxy: calibration and insights into model-data comparison, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18741, https://doi.org/10.5194/egusphere-egu26-18741, 2026.
In the present day, global oceans have absorbed most of the excess anthropogenic heat, abating surface temperature warming. The Mid-Pliocene Warm Period (MPWP; ~3.2 million years ago) is often cited as a potential analogue for future climate change due to atmospheric CO2 levels similar to today (~400 ppm) and global mean surface temperature ~2-4°C warmer than pre-industrial; the MPWP therefore offers a good opportunity to understand how a globally warmer climate stores oceanic heat. We use the PlioMIP2 model ensemble to quantify global ocean heat content (OHC), defined as that in the 0-700 m fixed-depth layer, to present an overview of the spatial characteristics of Indo-Pacific OHC during the MPWP, and to compare global OHC to future scenarios. Simulated MPWP OHC is globally higher than the pre-industrial except for in the Arabian Sea, where the lower OHC is attributed to weakened Northeast monsoon wind strength. Using the dt/dz definition of the thermocline, we find that the thermocline shoals over much of the northern Indian Ocean, including in the Arabian Sea, and deepens in the South China Sea; the equatorial Pacific thermocline warms by ~2°C from pre-industrial to the MPWP without deepening. Globally, MPWP OHC exceeds that of the highest SSP5-8.5 future scenario for the late 21st century (2081-2100). This suggests that the ocean can absorb substantial amounts of heat, though the dynamics of heat uptake remain important for abating surface temperature warming given potential nonlinearities.
How to cite: Grosvenor, H., Ford, H., Brierley, C., and Williams, C.: Ocean Heat Content in Warm Climates: Pliocene Simulations and Future Comparison , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3149, https://doi.org/10.5194/egusphere-egu26-3149, 2026.
With ongoing anthropogenic warming, the Arctic is increasingly dominated by thin, first-year ice. Understanding the ice-ocean-atmosphere interactions in warmer climates is therefore essential. We analyse the Arctic sea-ice energy budget in nine CMIP6-PMIP4 lig127k simulations of the Last Interglacial warm Arctic. All models show reduced Last Interglacial summer sea ice, but with substantial inter-model spread. We demonstrate that this arises from differences in surface energy anomalies, which is highly correlated with sea ice anomalies. Ice-albedo feedbacks dominate this response: reduced ice cover exposes more open ocean, enhances shortwave absorption, and warms the upper ocean. This heat is released in autumn, delaying sea-ice regrowth. Although modern anthropogenic warming is driven primarily by longwave forcing, our results highlight that shortwave absorption from reduced albedo is a key driver of summer sea-ice loss, underscoring the need for accurate representation of surface heat-balance processes in future Arctic projections. The Assessment Fast Track contains an idealised palaeoclimate experiment called abrupt127k, which is designed to explore Arctic sea ice response in CMIP7 models. We will, therefore, expand the analysis to include emerging CMIP7 results.
How to cite: Brierley, C., Pollock, M., Diamond, R., Heorton, H., Sime, L., and Schroeder, D.: An Arctic Sea Ice Energy Budget for the Last Interglacial, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9967, https://doi.org/10.5194/egusphere-egu26-9967, 2026.
The characteristics of multi-scale Asian summer monsoon (ASM) variability and corresponding dominating mechanisms since the Last Glacial Maximum (LGM) are investigated through model simulations, and also comparisons and assimilations with proxy records. The evolutions of ASM precipitation, oxygen isotope, and circulation are first investigated using the isotope-enabled transient experiment (iTraCE). On orbital and millennial scales, the monsoon variability are dominated mainly by external forcings (e.g., orbital parameter, ice sheet, melting water) through dynamic terms, while shorter scale monsoon variability are dominated mainly by internal variability (e.g., AMOC, AMV, PDV).
Then, high-resolution simulations of ASM precipitation are performed using dynamical downscaling through RegCM. The downscaled results show better consistence with proxy records. Paleoclimate data assimilation is applied to the model simulations to improve the underestimation of isotope and precipitation on orbital scale. Assimilated results show a new mega-tripolar pattern of ASM precipitation variations accompanying a continental‐wide enrichment of δ18O from the early to late Holocene over the entire ASM continental region. This pattern is dominated by the strengthening of westerly jet and weakening of ASM dominated by the precession. Characteristics of centennial scale ASM weakening events (such as 4.2 ka BP event) are also investigated using the assimilated results.
How to cite: Ning, L., Liu, Z., Liu, J., Yan, M., Cao, N., Xing, F., Chen, K., Sun, W., and Wen, Q.: Simulations and assimilations of Asian summer monsoon since LGM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2110, https://doi.org/10.5194/egusphere-egu26-2110, 2026.
It was well established that the East Asian summer monsoon experienced a long-term weakening during the transition from precession minimum (Pmin) to maximum (Pmax), but how the leading monsoonal precipitation modes at interdecadal/interannual timescale superimposing on this weakening trend may vary remains unknown, owing to the dispersively distributed proxies and their coarse resolution. To address this challenge, we perform a transient global climate simulation at ~1° resolution during 130–115 ka that encompasses the transition from Pmin (~127 ka) to Pmax (~116 ka). We demonstrate that the first leading mode of summer precipitation over eastern China shifted from monopole to dipole patterns during the Pmin-to-Pmax transition, with the second leading mode switching from dipole to tripole patterns. The shifts of precipitation modes were shaped by the southward shift of the regressed atmospheric circulation systems at interdecadal/interannual timescale during the Pmin-to-Pmax transition, which were further regulated by the long-term southward retreat and weakening of the East Asian summer monsoonal circulations due to decreased summer insolation. This elucidated interdecadal/interannual drought-flood variability superimposing on the long-term weakening of the East Asian summer monsoon, which may provide insight into how gradual orbital changes reorganize short-term precipitation variability and shed light on ecological civilizations over East Asia during the Pmin-to-Pmax transition.
How to cite: Jiang, N. and Yan, Q.: Precession-Induced Regime Shift of Summer Precipitation Leading Modes over Eastern China across the Last Interglacial, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3252, https://doi.org/10.5194/egusphere-egu26-3252, 2026.
The variation of the upper-level subtropical westerly jet over East Asia (EASWJ) in summer during the last deglaciation (LD) and its impact on precipitation distributions in China are investigated using a set of transient simulation. The results show that the EASWJ variability during the LD is characterized by a millennial variation along with a weakening trend. The millennial variation of the EASWJ can lead to a north-south dipole precipitation pattern in eastern China and a uniform precipitation pattern in northern China. The weakening trend of the EASWJ is accompanied with a tripole precipitation pattern in eastern China and a uniform precipitation pattern in northern China. The millennial EASWJ variability is related to the millennial AMOC variability, which is induced by the meltwater flux. The weakening trend is attributed to the warming trend induced by the orbital parameters. Due to the different warming structure, the EASWJ change driven by the greenhouse gas, which is strengthening, is different from that driven by the orbital parameters, although they both tend to lead to a warming trend. Our findings may have implications to better understanding the regional westerly jet variation in response to global climate change, especially the global warming.
How to cite: Yan, M. and Wang, J.: Variation of the summer westerly jet in East Asia during the last deglaciation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2389, https://doi.org/10.5194/egusphere-egu26-2389, 2026.
The South Asian summer monsoon (SASM) rainfall exerts a profound influence on the densely populated region and its surrounding oceans. Giving synchronous rainfall changes across the South Asian continent (SAC) and the Bay of Bengal (BoB) in the current climate, both terrestrial and marine proxies are widely used to reconstruct the past SASM variations. However, earlier studies based on proxy records and climate models have suggested an increased rainfall over SAC and a decreased rainfall over BoB at the mid-Holocene, challenging the traditional view of synchronous rainfall variation between SAC and BoB.
Using the TraCE-21ka simulation and PMIP4 models, this study delves into the underlying mechanisms of the opposite land-ocean rainfall response in MH, underscoring the crucial role of North Africa rainfall anomaly in remotely regulating the BoB rainfall. During the boreal summer, enhanced insolation amplified the land-sea thermal gradient, which further intensifies the southwest monsoon and thus leads to an increased SAC rainfall. Conversely, the reduction in BoB rainfall can be attributed to the weakness of monsoon trough circulation triggered by increased rainfall over North Africa. The North African rainfall anomaly excites Kelvin waves to its east, consequently resulting in anomalous easterlies over the northern Indian Ocean and anticyclonic circulation over the BoB. These findings not only deepen our grasp of the SASM system, but provides essential insights for interpreting the marine sedimentary records and projecting the future SASM responses.
How to cite: Wang, T., Wen, Q., Liu, J., Liu, Z., Ning, L., Yan, M., and Sun, W.: Opposite terrestrial and marine South Asian summer monsoon rainfall response at Mid-Holocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2017, https://doi.org/10.5194/egusphere-egu26-2017, 2026.
