15 July 2016

Volcanic Effects on Climate

Science

Objective
• To understand and interpret results published by Johansson et al. in a 2015 paper in Nature Climate Change

Research

• To determine why Johansson et al. obtained very small estimates of the surface cooling (-0.2°C) and the net radiative forcing (-1W/m2) caused by the eruption of Pinatubo

Impact
  •  Johansson et al.’s estimate of the radiative forcing from Pinatubo is 2.5 to 5 times smaller than the forcing inferred from direct and indirect observations

  • •  Future Bayesian studies seeking to estimate volcanic cooling signals should incorporate beOer observational constraints (like ISCCP and CERES measurements of net radiative fluxes)

  • •  Johansson et al.’s estimate of volcanically-caused surface temperature changes during the “hiatus” period does not accurately reflect known shortcomings and uncertainties in volcanic forcing

Summary

The paper attempts to understand and interpret results published by Johansson et al. in a 2015 paper in Nature Climate Change. It shows that Johansson et al.’s estimate of the radiative forcing from Pinatubo is 2.5 to 5 times smaller than the forcing inferred from direct and indirect observations. Our research provides scientific motivation for incorporating better observational constraints (like ISCCP and CERES measurements of net radiative fluxes) in Bayesian studies that seek to estimate volcanically induced cooling signals.
 

Contact
Benjamin Santer
Lawrence Livermore National Laboratory (LLNL)
Publications
2016.  "Correspondence: Volcanic effects on climate."  Nature Climate Change 6: 3-4, doi:10.1038/nclimate2859.