AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Radiative and Climate Impacts of Concurrent Stratospheric Sulfur Geoengineering and a Large Volcanic Eruption
ANTON LAAKSO, Antti-Ilari Partanen, Harri Kokkola, Ulrike Niemeier, Claudia Timmreck, Kari Lehtinen, Hannele Korhonen, Finnish Meteorological Institute
Abstract Number: 119 Working Group: Aerosols, Clouds, and Climate
Abstract Solar radiation management (SRM) by stratospheric sulfur injection is one of the most discussed and probably the most cost effective geoengineering method. Injecting sulfur to the stratosphere could be seen as an analogy of large volcanic eruptions, where large amounts of sulfur dioxide are released into the stratosphere. In the atmosphere SO2 oxidizes and forms aqueous sulfuric acid aerosols which reflect incoming solar radiation back to space. If SRM is ever used to cool the climate it is possible that a huge volcanic eruption could happen also during the SRM, which would lead temporally to a very strong cooling.
Simulations have been performed in two steps. In the first step, we have used the aerosol-climate model MAECHAM5-HAM-SALSA to define aerosol fields. In the second step of the study we have performed climate simulations using Max-Planck-Institute's Earth system model (MPI-ESM) by using aerosol fields defined by MAECHAM5-HAM-SALSA. We studied scenarios of volcanic eruptions in two different locations and seasons and during the SRM sulfur injections and without injections.
Sulfate burden and radiative forcing after the volcanic eruption decrease clearly faster if volcanic eruption happens during the geoengineering injections. In this situation, sulfur from the eruption does not only form new particles but it also condenses into pre-existing particles. This leads to larger particles which lifetime is shorter. Because there is less and larger particles, the effect to the shortwave radiation is smaller. Thus the global mean temperature would have returned to the level before the eruption faster after volcanic eruption during SRM than normal atmospheric conditions. This also means that observations of strong volcano eruptions cannot be applied when estimating the consequences of an eruption during geoengineering. If the eruption took place in the high latitudes, the resulting global forcing would be highly dependent on the season of the eruption.