Unknown Eruption Source Parameters Cause Large Uncertainty in Historical Volcanic Radiative Forcing Reconstructions

• Main Authors: Marshall, Lauren R., Schmidt, Anja, Johnson, Jill S., Mann, Graham W., Lee, Lindsay A., Rigby, Richard, Carslaw, Ken S.
• Format: Text
• Language: unknown
• Published: Apollo - University of Cambridge Repository 2021
• Subjects: ATMOSPHERIC COMPOSITION AND STRUCTURE; Volcanic effects; Air/sea constituent fluxes; BIOGEOSCIENCES; Climate dynamics; Modeling; COMPUTATIONAL GEOPHYSICS; Numerical solutions; CRYOSPHERE; Avalanches; Mass balance; GEODESY AND GRAVITY; Ocean monitoring with geodetic techniques; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Global change from geodesy; GLOBAL CHANGE; Abrupt/rapid climate change; Climate variability; Earth system modeling; Impacts of global change; Land/atmosphere interactions; Oceans; Regional climate change; Sea level change; Solid Earth; Water cycles; HYDROLOGY; Climate impacts; Hydrological cycles and budgets; INFORMATICS; MARINE GEOLOGY AND GEOPHYSICS; Gravity and isostasy; ATMOSPHERIC PROCESSES; Climate change and variability; Climatology; General circulation; Ocean/atmosphere interactions; Regional modeling; Theoretical modeling; OCEANOGRAPHY GENERAL; Climate and interannual variability; Numerical modeling; NATURAL HAZARDS; Atmospheric; Geological; Oceanic; Physical modeling; Climate impact; Risk; Disaster risk analysis and assessment; OCEANOGRAPHY PHYSICAL; Air/sea interactions; Decadal ocean variability; Ocean influence of Earth rotation; Sea level variations and mean; Surface waves and tides; Tsunamis and storm surges; PALEOCEANOGRAPHY; POLICY SCIENCES; Benefit‐cost analysis; RADIO SCIENCE; Radio oceanography; SEISMOLOGY; Earthquake ground motions and engineering seismology; Volcano seismology; VOLCANOLOGY; Volcano/climate interactions; Atmospheric effects; Volcano monitoring; Effusive volcanism; Mud volcanism; Explosive volcanism; Volcanic hazards and risks; Research Article; volcanic radiative forcing; statistical emulation; volcanic aerosol; sulfate deposition; volcanic eruptions; ice core; Ice Sheet
• Online Access: https://dx.doi.org/10.17863/cam.71952; https://www.repository.cam.ac.uk/handle/1810/324499

Funder: U.K. China Research and Innovation Partnership Fund : Funder: National Centre for Atmospheric Science (NCAS); Id: http://dx.doi.org/10.13039/501100000662 : Abstract: Reconstructions of volcanic aerosol radiative forcing are required to understand past climate variability. Currently, reconstructions of pre‐20th century volcanic forcing are derived from sulfate concentrations measured in polar ice cores, mainly using a relationship between the average ice‐sheet sulfate deposition and stratospheric sulfate aerosol burden based on a single explosive eruption—the 1991 eruption of Mt. Pinatubo. Here we estimate volcanic radiative forcings and associated uncertainty ranges from ice‐core sulfate records of eight of the largest bipolar deposition signals in the last 2,500 years using statistical emulation of a perturbed parameter ensemble of aerosol‐climate model simulations of explosive eruptions. Extensive sampling of different combinations of eruption source parameters using the emulators reveals that a very wide range of eruptions in different seasons with different sulfur dioxide emissions, eruption latitudes, and emission altitudes produce ice‐sheet sulfate deposition consistent with ice‐core records. Consequently, we find a large range in the volcanic forcing that can be directly attributed to the unknown eruption source parameters. We estimate that the uncertainty in volcanic forcing caused by many plausible eruption realizations leads to uncertainties in the global mean surface cooling of around 1°C for the largest unidentified historical eruptions. Our emulators are available online (https://cemac.github.io/volcanic-forcing-deposition) where eruption realizations for given ice‐sheet sulfate depositions can be explored.