Dr. Valentina Aquila
Assistant Professor, Dept of Environmental Science
American University, Washington DC

Title: Climate impacts of the Mount Pinatubo eruption: from the stratosphere to the troposphere

Abstract: Valentina Aquila, Department of Environmental Science, American University, Washington DC

Large explosive volcanic eruptions can increase the stratospheric aerosol load by orders of magnitude and impact the climate at a global scale. Volcanic eruptions inject sulfur dioxide (SO2) in the stratosphere, where it nucleates and condenses to form sulfate aerosols. These aerosols scatter shortwave radiation, cooling the global mean surface temperature, and absorb infrared and near-infrared radiation, warming the lower stratosphere. To date, the largest volcanic eruption to be extensively characterized using satellite observations is that of Mt. Pinatubo, Philippines on June 15th, 1991. Volcanic aerosols from Mt. Pinatubo reached up to 30 km altitude and were still detected in the atmosphere five years after the eruption. During this period, they acted as a major forcing on the Earth’s climate. In the stratosphere, aerosol from Mt. Pinatubo led to chemical ozone depletion and changes in the Brewer-Dobson circulation. In the troposphere, the volcanic radiative forcing caused a cooling of the global mean temperature as large as 0.5˚C despite the development of El Niño in 1991-1992. In this talk, I will present results from simulations with the Goddard Earth Observing System (GEOS) that identify the effects of the Mt. Pinatubo eruption on atmospheric temperatures and composition. I will focus on the role of Mt. Pinatubo in changes in stratospheric ozone concentrations and temperatures, isolating the effects of Mt. Pinatubo from the effects of other forcings and its role in the development of the 1991-1992 El Niño.