Volcanic stratospheric sulfur injections from 500 BCE to 1900 CE, eVolv2k_version4

Based on sulfate records from a suite of ice cores from Greenland and Antarctica, the eVolv2k database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events from 500 BCE to 1900 CE. We combined three ice-core records from Greenland and 18 from Antarctica, to determine the timing of past eruptions and the cumulative sulfate mass deposition over the polar ice sheets for 256 volcanic eruptions. Version 4 of this database incorporates improvements to the ice-core records based on 1) geochemical characterization of tephra to constrain the source volcano and its latitude (e.g. Ilopango, Okmok, Taupo), 2) sulfur isotope analyses to constrain volcanic plume height, e.g. for Samalas (Indonesia, 1257), Kuwae (Vanuatu, 1458), Tambora (Indonesia, 1815) and the proximity of the source eruptions relative to the ice sheets and 3) tree-ring records (i.e. frost rings, Miyake events) and documentary evidence (volcanic dust veils and dark lunar eclipses) to constrain the timing for specific volcanic eruptions. With several eruptions precisely tied to the exact years (e.g. in 536, 626, 946, 1257, 1477, 1783) we estimate an age uncertainty of less than ±1-2 years over the past 1500 years, and less than ±2-3 years between 500 BCE to 500 CE. We attributed 41 VSSI events to known volcanic eruptions and provided default latitudes of 45°N and 45°S to VSSI events only detected in the ice cores of the respective hemisphere. VSSI events which were detected in the ice sheets of both hemispheres were attributed by default to the tropics (0°). Overall, the 256 volcanic eruptions injected 1220 Tg of sulfur (TgS) into the stratosphere which equates to a long-term mean of 0.5 TgS/yr. 49% of the eruptions occurred in the Northern Hemisphere extra-tropics, 28% in the tropics and 23% in the Southern Hemisphere extra-tropics. The three largest eruptions were Samalas (1257), an unidentified eruption in the tropics in 426 BCE and Okmok II (Alaska in 43 BC). The 13th century (rank 1), the 19th century (rank 2) and the 6th century (rank 3) were the most active periods exceeding the long-term annual mean VSSI from major volcanic eruptions by 80 to 140 %. These periods are linked to overall cold climates promoting glacier expansions in the Northern Hemisphere. Periods of decreased volcanic activity occurred between 950 and 1100 CE (Medieval Quiet Period) and from 40 BCE to 160 CE (Roman Quiet Period). During these time intervals annual mean VSSI was 55 to 70 % less than the long-term mean. The eVolv2k database is the recommended volcanic forcing by the Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the PMIP (PMIP4) such as the past1000 transient simulations (Jungclaus et al., 2017). Version 4 of this database replaces the previous version eVolv2k_v3: an ice-core based volcanic stratospheric sulfur injection dataset version 3, https://www.wdc-climate.de/ui/entry?acronym=eVolv2k_v3.