What We Can Learn from the Next Large Volcanic Eruption

Abstract:

The April 1982 eruption of El Chichón in México stimulated interest in the climate response to volcanic eruptions and produced very useful observations and modeling studies. The last large volcanic eruption, the June 15, 1991 eruption of Mt. Pinatubo in the Philippines, was the best observed eruption ever, and serves as a canonical example for studies of aerosol production and transport, climate response, and deposition on ice sheets. However, many aspects of both eruptions were poorly observed, climate model simulations of the response are imperfect, and new scientific issues, such as stratospheric sulfate geoengineering, raise new scientific questions that could be answered by better observations of the next large volcanic eruption. In this talk I will summarize what we know and do not know about large volcanic eruptions, and discuss new questions that can be addressed by being prepared for the next large eruption. These include:

• How and how fast will SO₂ convert to sulfate aerosols?
• How will the aerosols grow?
• What will be the size distribution of the resulting sulfate aerosol particles?
• How will the aerosols be transported throughout the stratosphere?
• How much fine ash gets to the stratosphere, how long does it stay there, and what are its radiative and chemical impacts?
• How will temperatures change in the stratosphere as a result of the aerosol interactions with shortwave (particularly near IR) and longwave radiation?
• Are there large stratospheric water vapor changes associated with stratospheric aerosols? Is there an initial injection of water from the eruption?
• Is there ozone depletion from heterogeneous reactions on the stratospheric aerosols?
• As the aerosols leave the stratosphere, and as the aerosols affect the upper troposphere temperature and circulation, are there interactions with cirrus and other clouds?