The European summer of 1816 has often been referred to as a “year without a summer” due to anomalously cold conditions and unusual wetness, which led to widespread famines and agricultural failures. The cause has often been assumed to be the eruption of Mount Tambora in April 1815, however this link has not, until now, been proven. Here we apply state-of-the-art event attribution methods to quantify the contribution by the eruption and random weather variability to this extreme European summer climate anomaly. By selecting analogue summers that have similar sea-level-pressure patterns to that observed in 1816 from both observations and unperturbed climate model simulations, we show that the circulation state can reproduce the precipitation anomaly without external forcing, but can explain only about a quarter of the anomalously cold conditions. We find that in climate models, including the forcing by the Tambora eruption makes the European cold anomaly up to 100 times more likely, while the precipitation anomaly became 1.5-3 times as likely, attributing a large fraction of the observed anomalies to the volcanic forcing. Our study thus demonstrates how linking regional climate anomalies to large-scale circulation is necessary
to quantitatively interpret and attribute post-eruption variability.
The Model data consists 50 HadCM3 Model simulations with volcanic forcing for the period 01/12/1814 to 01/12/1816.
The dataset is divided into atmosphere monthly mean and ocean monthly mean files. With each containing 24 monthly values for each of the 50 simulations.
The files are in the UK Metoffice pp format. This can be read using the iris python package:
Example_script.py is an example of a simple python script which reads the model data.
Schurer, Andrew. (2019). HadCM3 Model data used in the article "Disentangling the causes of the 1816 European year without a summer" by Schurer, Andrew; Hegerl, Gabriele; Luterbacher, Juerg; Broennimann, Stefan; Cowan, Tim; Tett, Simon; Zanchettin, Davide; Timmreck, Claudia, [dataset]. University of Edinburgh. School of GeoSciences. Institute of Geography. https://doi.org/10.7488/ds/2601.