EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The unidentified volcanic eruption of ~1809: why it remains a climatic cold case

Claudia Timmreck1, Matthew Toohey2, Davide Zanchettin3, Stefan Brönnimann4, Elin Lundstadt4, and Robert Wilson5
Claudia Timmreck et al.
  • 1Max-Planck-Institut für Meteorologie, Atmosphere in the Earth System, Hamburg, Germany (
  • 2Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Canada
  • 3Department of Environmental Sciences, Informatics and Statistics, University Ca’ Foscari of Venice, Mestre, Italy
  • 4Institute of Geography Climatology and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 5School of Earth & Environmental Sciences, University of St. Andrews, United Kingdom

The  "1809 eruption” is one of the most recent unidentified volcanic eruptions with a global climate impact. Even though the eruption ranks as the 3rd largest since 1500 with an eruption magnitude estimated to be two times that of the 1991 eruption of Pinatubo, not much is known of it from historic sources. Based on a compilation of instrumental and reconstructed temperature time series, we show here that tropical temperatures show a significant drop in response to the ~1809 eruption, similar to that produced by the Mt. Tambora eruption in 1815, while the response of Northern Hemisphere (NH) boreal summer temperature is spatially heterogeneous.  Here, we present the sensitivity of the climate response simulated by the MPI Earth system model to a range of volcanic forcing estimates constructed using estimated volcanic stratospheric sulfur injections (VSSI) and uncertainties from ice core records. Three of the forcing reconstructions represent a tropical eruption with approximately symmetric hemispheric aerosol spread but different forcing magnitudes, while a fourth reflects a hemispherically asymmetric scenario without volcanic forcing in the NH extratropics. Observed and reconstructed post-volcanic surface NH summer temperature anomalies lie within the range of all the scenario simulations. Therefore, assuming the model climate sensitivity is correct, the VSSI estimate is accurate within the uncertainty bounds. Comparison of observed and simulated tropical temperature anomalies suggests that the most likely VSSI for the 1809 eruption would be somewhere between 12 -19 Tg of sulfur. Model results show that NH large-scale climate modes are sensitive to both volcanic forcing strength and its spatial structure.  While spatial correlations between the N-TREND NH temperature reconstruction and the model simulations are weak in terms of the ensemble mean model results, individual model simulations show good correlation over North America and Europe, suggesting the spatial heterogeneity of the 1810 cooling could be due to internal climate variability. 

How to cite: Timmreck, C., Toohey, M., Zanchettin, D., Brönnimann, S., Lundstadt, E., and Wilson, R.: The unidentified volcanic eruption of ~1809: why it remains a climatic cold case, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5330,, 2021.

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