Climate of the eastern Mediterranean and Middle East in the 6th century CE with COSMO-CLM

The climate of the eastern Mediterranean and the Middle East is well documented in natural (speleothems, tree rings, sediments and pollen) and human-historical archives. The 6th century CE is of particular interest from both a historical and climatic perspective. It is a period of prosperity for the Eastern Byzantine Empire and political stability, but also a time when there was a heavily debated plague pandemic and significant climate variability associated with a major cluster of volcanic eruptions. Dynamical downscaling can bridge the gap between palaeo-records and climate reconstructions, which can be affected by various sources of uncertainty, and the coarsely resolved Earth System Models (ESMs) with 200 km or more horizontal resolution. A transient paleo-simulation with the appropriately adjusted regional climate model COSMO-CLM (CCLM, COSMO 5.0 clm16) is carried out to investigate possible links and feedbacks between the socio-political and economic conditions and the climate variability of that period in more detail.

The state-of-the-art and CMIP6 compliant forcing reconstructions of volcanic (stratospheric aerosol optical depth), orbital (eccentricity, obliquity, precession), solar (irradiance), land-use and greenhouse-gas changes used for the MPI-ESM-LR (Jungclaus et al. 2017) are therefore implemented in the regional climate model. The simulated temperature and precipitation are compared with those of other CMIP6 models as well as with proxy records and reconstructions. In connection with the two successive volcanic eruptions in 536 and 540 CE, the annual temperature of the entire region dropped noticeably until about 550 CE. The signal for precipitation is not as clear, but the years of the eruptions are the driest of the century in the eastern Sahara and Arabian Peninsula and the wettest in the eastern Mediterranean.