Roman Warm Period and Late Antique Little Ice Age in an Earth System Model Large Ensemble

Changes in climate during the Roman Warm Period (RWP, 1–250 CE) and Late Antique Little Ice Age (LALIA, 536–660 play a critical role early societal evolution, but differences between these two periods possible causes of changes remain poorly explored. Here we use LOch–Vecode-Ecbilt-CLio-agIsM model Large Common Era Ensemble with 70 members to examine change over intervals compare results this ensemble latest temperature reconstructions from Past Global 2k network transient simulation for past 2,000 years Community Earth System Model. Results both proxy simulations show warming mid-to-high latitudes Northern Hemisphere (NH) RWP compared LALIA. This is likely linked increased radiative forcing associated weaker volcanic eruptions RWP, which reduced sea ice area pronounced high-latitude through surface albedo lapse-rate feedbacks. increases upper ocean heat content centennial time scales maintain NH regions. Moreover, has drier (wetter) conditions eastern (western) equatorial Pacific than LALIA, related zonal gradient modification circulation.