Large volcanic eruptions produce stratospheric sulfate aerosols that can persist for one to two years following the eruption. In addition to a reduction in global-mean temperature over this time period, the aerosols can produce regional climatic responses including reductions in tropical monsoon rainfall, winter warming over the Northern Hemisphere continents, and possibly an increase in the likelihood of El Nino events. While these effects may only last for one or two years, the impact on subsurface ocean temperatures can last longer, up to several decades for water masses below the thermocline.
This project seeks to determine the extent to which the above climatic consequences are predictable. While the eruptions themselves are not predictable, the amount of sulfate injected into the stratosphere can be determined within days of an eruption, and this information may suffice to determine the volcanic influence over the years to decades following an eruption.
A large part of the research effort is devoted to identifying the volcanic signal in climate simulations from multi-model ensembles including the Coupled Model Intercomparison Project versions 3 and 5 (CMIP3, CMIP5), the Paleoclimate Model Intercomparison Project versions 2 and 3 (PMIP2, PMIP3), and the NCAR Large Ensemble (LE) and Past Millenium (PM) simulations. Several aspects of the simulations will be evaluated as part of this effort, including the nature of the volcanic forcing used, the state of the atmosphere and ocean (in terms of climatic fluctuations associated with El Nino and other climate modes) at the time of the eruption, and the effect of the eruption on stratospheric ozone. Following this analysis the Principal Investigator and his team will conduct a suite of climate simulations with the Community Earth System Model version 1 (CESM1). A number of simulations will be performed including simulations of past volcanic eruptions and simulations of eruptions starting at specific climate states (e.g. the warm and cold phases of El Nino). Simulations will also consider the predictability of climatic effects as a function of the size, location (particularly high latitude versus low latitude), and time of year of the eruption.
The work has societal broader impacts due to the substantial human impacts that eruption-induced climate fluctuations can have. Work performed under this award could contribute to the development of a forecasting system for the long-term climatic disruptions following volcanic eruptions, which would enable adaptation efforts for communities likely to be adversely affected. In addition, the project supports a graduate student and a postdoctoral research associate, thereby providing for the future scientific workforce in this research area.
