Supported by an Accelerated Scientific Discovery (ASD) Derecho computing grant (ACGD0008 to Otto-Bliesner; PaleoWeather), high-resolution Community Earth System Model (CESM-HR) simulations of the Early Eocene Climatic Optimum (EECO, ~50 million years ago) have been completed. The high-resolution simulations also include water isotope capability, enabling direct comparisons with isotope records of past and present climate change from a range of archives. The simulations followed the protocols of the Deep-time Model Intercomparison Project (DeepMIP) and were conducted at atmospheric CO2 concentrations of 3× and 6× preindustrial levels (284.7 ppmv) to span the plausible CO2 range inferred from the geological record. Each simulation was initialized from a near-equilibrated, low-resolution companion simulation and integrated for 60 years. Further details of the experimental design and simulation results can be found in Zhu et al. (2026; DOI: 10.21203/rs.3.rs-9097760/v1).

The EECO dataset is one of four high-resolution simulation datasets produced through the ASD PaleoWeather project. The other datasets represent the Preindustrial (21 TB), Last Glacial Maximum (29 TB), and mid Pliocene Warm Period (28 TB). Establishing separate GDEX dataset records for each period will allow the respective leads who set up and ran the simulations to serve as leads for the corresponding DOI. Each GDEX landing page will include links to the other PaleoWeather simulations, enabling discovery and comparison across climate periods.

To our knowledge, the ASD PaleoWeather collection represents the first high-resolution paleoclimate simulation suite of this kind made available to the community. Its horizontal grid spacing is approximately ten times finer than traditional climate-model configurations, which typically use resolutions of 1-2 degrees. The CESM-HR resolution more realistically represents synoptic and mesoscale atmospheric and oceanic phenomena, together with their interactions with large-scale circulation.

The EECO dataset will support research on weather-climate interactions in a warm-climate state, including studies of extreme events such as heat waves, atmospheric rivers, and tropical cyclones. More broadly, the PaleoWeather simulations complement the MESACLIP historical and future simulations, providing opportunities to investigate links between climate and weather extremes across Earth's past, present, and future climate states.