Quantifying the Impact of Volcanic Aerosol Forcing Uncertainties on Lower Troposphere Temperature

• Activity Number: 602
• Type: Contributed
• Date/Time: Wednesday, August 12, 2015 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics and the Environment
• Author(s): Francisco Beltrán* and Benjamin D. Santer and Gardar Johannesson
• Companies: Lawrence Livermore National Laboratory and Lawrence Livermore National Laboratory and Lawrence Livermore National Laboratory
• Keywords: Volcanic Aerosols ; External Forcing ; Bayesian Modeling ; Atmospheric Data

Abstract

We present a general methodology to de-convolve climate data into important patterns such as natural internal variability, external forcing signals, and trends, in an effort to analyze the impact of external forcing uncertainties. This work primarily focuses on the treatment of volcanic aerosol forcings over the period 1979 to 2012 and it's effect on the observed trend. We use a Bayesian framework to jointly estimate the volcanic effect on satellite derived lower tropospheric temperature (TLT) while also capturing the variability induced by El Niño/Southern Oscillation (ENSO). The volcanic signal is analyzed under four different scenarios: No volcanic activity; El Chichón and Pinatubo eruptions only; No 21st century volcanic activity; and inclusion of 21st century volcanic activity. Our analysis clearly illustrates the discrepancies in observed trend under the different treatments of the volcanic aerosol forcings. We conclude that correctly depicting volcanic aerosol forcings is vital in properly representing TLT. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.