Earth System Model Response to Large Midlatitude and High-latitude Volcanic Eruptions

We used the Meteorological Research Institute Earth System Model to simulate the climate response to massive sulfur dioxide (SO2) emission from the volcanic eruptions of Paektusan (China/North Korea) and Eldgja (Iceland) into the stratosphere in the tenth century Common Era (CE). Assuming 3 times the SO2 emission of the 1883 Krakatau eruption, as recorded by Greenland ice core sulfate concentrations, simulations of Paektusan and Eldgja had roughly similar global mean impacts within 2 years of erupting: decreases in surface insolation (-10 W/m(2), -5%), surface air temperature (-1 degrees C), land net primary production (NPP; -3 GtC/year, -5%), and soil respiration (-5 GtC/year, -10%). While both simulations had severe impacts on the extratropical Northern Hemisphere, the simulated response to Paektusan is twice as strong as Eldgja in the tropics (cooling [1 degrees C], precipitation decrease [10%], and NPP increase [7%]). Simulation-Eldgja had almost no impact on the extratropical Southern Hemisphere because of its initial latitude. These regional differences combine so that Simulation-Paektusan has slightly larger global mean impacts, including an atmospheric CO2 decrease of similar to 2 ppm. Tropical NPP primarily increases due to the fact that photosynthesis maximizes at temperatures below the tropical mean temperature and secondarily to the cooling-induced decrease in respiration, which indicates relatively rich tropical harvests despite large volcanic eruptions. In contrast, the severe cooling (-2.5 degrees C) and decreased NPP (-20%) in the northern extratropics could mean poor harvests and famines, which can lead to social turmoil such as a rebellion in northeast Japan around the same time as the eruptions.