Climate Impact from Inter-Hemisphere Asymmetric Volcanic Eruptions in the FLOR Ensemble Modelling

Explosive volcanic eruptions have a great impact on the global climate system. Yet how the impact depends on the spatial structure of each eruption is not clear. In this study, we show that there are three types of large volcanic eruptions in the 20th century according to the inter-Hemispheric forcing structure: symmetric, Southern Hemispheric and Northern Hemispheric, which are represented by the 1991 Pinatubo, 1963 Agung and 1902 Santa Maria eruptions, respectively. Using the Forecast-Oriented Low Ocean Resolution (FLOR) version of the GFDL climate model CM2.5, we conduct 30-member ensemble simulations for each of the three volcanic eruptions. We find that the two asymmetric eruptions, although weaker than the symmetric (Pinatubo) eruption in terms of global mean surface temperature response, can have comparable response in the Hemisphere where the eruption occurs. More importantly, the two asymmetric eruptions have an even stronger impact in hydroclimate, pushing the ITCZ away from the eruption Hemisphere. Different responses of hurricane activity are also seen from the simulations. Our findings demonstrate the importance to distinguish climate impacts from volcanic forcings of different spatial structures.