B-WP1 - ALARM-II: Alert for LARge volcanic eruptions in Medium term climate prediction II

Project aims

Including volcanic forcing in the MiKlip prediction system has increased the prediction skill for global surface temperature (Timmreck et al., 2016). However, the regional impacts of volcanic forcing, in particular on the Northern Hemisphere (NH) winter climate, which are controlled largely by dynamical changes, are neither fully understood nor well represented in the current prediction system. ALARM-II will therefore explore and improve the representation of the climate response to aerosol perturbations caused by volcanic eruptions in the MiKlip prediction system, in order to prepare for future events and be able to forecast their effects immediately after a potential future eruption.

Project structure

ALARM II consists of three workpackages and is coordinated by Dr. Claudia Timmreck (MPI-M). Dr. Hauke Schmidt (MPI-M) and Prof. Dr. Kirstin Krüger (UiO), as an external partner, contribute to the project.

Tasks of the projects

  1. ALARM-II studies all seasons, but focusses especially on NH winter climate. Here exists the highest regional uncertainty in mid-term climate prediction for Europe after a large volcanic eruption. NH winter climate responses to external forcing presumably depend on the preconditioning of the polar vortex and the resolution of the prediction system.
  2. ALARM-II investigates if seasonal and decadal predictions after a large volcanic eruption can be improved if volcanically induced ozone changes are taken into account.
  3. The Coupled Model Inter Comparison Phase 6 (CMIP6) experiments investigate the impact of future volcanic eruptions on seasonal and decadal climate predictions. ALARM-II plays a leading role in the planning, analysis and interpretation of these, based on the experience gained in MiKlip.


  • Recommendation regarding the applied model configuration for post-volcanic studies.
  • Improved understanding of the impact of model background state and variability in response to volcanic forcing.
  • Assessment of the impact of volcanically induced ozone changes on the predictability of NH climate.
  • Synthesis of the seasonal and decadal post-volcanic response in a multi-model framework.
  • Updated version of the MiKlip volcanic impact recipe.

Progress so far

A multilinear regression analysis of five historical runs with the MPI-ESM-HR and CMIP5 forcing shows that the MPI-ESM-HR model reacts qualitatively similar, in the middle atmosphere to natural and anthropogenic forcings, to the MPI-ESM-LR and the MPI-ESM-MR model (see Schmidt et al., 2013). The temperature response to volcanic eruptions shows the typical pattern of a tropospheric cooling and a warming in the low to mid-latitude lower stratosphere. The meridional temperature signal from volcanic forcing is reflected in the westerly wind anomalies in large parts of the stratospheric high-latitudes. It is, however, difficult to interpret the difference between the model versions, as the volcanic signal is masked by the high interannual variability in NH winter. The large ensemble (≥25) of the planned VolMIP (Model Intercomparison Project on the climatic response to Volcanic forcing) Pinatubo simulations (Zanchettin et al., 2016) with the MPI-ESM in LR (low resolution) and HR (high resolution) will offer a great possibility to study the effect of an increased model resolution with an ensemble sufficiently large to get a significant response.

Figure 1: Multi-model mean of the zonal mean zonal wind anomaly in the first winter after the nine strongest tropical eruptions since 1880 (left) and after the two strongest eruptions since 1880 – Krakatau and Pinatubo (right). Stippling indicates where at least 14 of 15 models agree on the sign of the anomaly. Figure from Bittner et al. (2016).

The MPI Grand Ensemble, a 100-member ensemble of historical (1850–2005) simulations with the MPI-ESM-LR, has been analysed with focus on the stratospheric temperature and wind response in the 1st post volcanic NH winter (Bittner et al., 2016). Approximately 15 ensemble members are needed to get a significant (95%) response of the NH polar vortex in December to February (DJF) after the Pinatubo eruption. The amount of necessary ensemble members for a significant response depends on the magnitude of the anomaly and the interannual variability. Including smaller eruptions to increase the sample size does not necessarily improve the detectability of the volcanic signal. Analysing the dynamical response to volcanic eruptions in too small ensembles might therefore lead to false conclusions. Hence, the CMIP5 models do not generally fail to capture the dynamical response to tropical volcanic eruptions (Figure 1). Large uncertainties remain in the response of the real atmosphere to volcanic eruptions due to the small number of observed events.

To address the question how does the pre-eruption climate state influence the impact of the volcanic signal on the prediction, we have performed together with Module D FLEXFORDEC/INTEGRATION decadal forecasts with the MiKlip prediction system, for the initialisation years 2012 and 2014, which differ in the Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO) phase llling et al (2018). Each forecast contains an artificial Pinatubo-like eruption starting in June of the first prediction year and consists of 10 ensemble members. Our results show that the average global cooling response over 4 years of about 0.2 K and the precipitation decrease of about 0.025 mm day−1 is relatively robust throughout the different experiments and seemingly independent of the initialisation state. However, on a regional scale, we find substantial differences between the initialisations. The cooling effect in the North Atlantic and Europe lasts longer and the Arctic sea ice increase is stronger in the simulations initialised in 2014. In contrast, the forecast initialised in 2012 with a negative PDO shows a prolonged cooling in the North Pacific basin.


  • Bittner, M., H. Schmidt, C. Timmreck and F. Sienz (2016) Using a large ensemble of simulations to assess the Northern Hemisphere stratospheric dynamical response to tropical volcanic eruptions and its uncertainty, Geophys. Res. Lett., 43, doi:10.1002/2016GL070587.
  • Schmidt, H., S. Rast, F. Bunzel, M. Esch, M.A. Giorgetta, S. Kinne, T. Krismer, G. Stenchikov, C. Timmreck, L. Tomassini  and M. Walz (2013). The response of the middle atmosphere to anthropogenic and natural forcing in the CMIP5 simulations with the MPI-ESM., Journal of Advances in Modeling Earth Systems (JAMES), 5, 98-116, doi: 10.1002/jame.20014.
  • Timmreck, C., H. Pohlmann, S. Illing and C. Kadow (2016). The impact of stratospheric volcanic aerosol on decadal scale predictability. Geophys. Res. Lett, 43, doi: 10.1002/2015GL067431.
  • Zanchettin, D., M. Khodri, C. Timmreck, et al. (2016). The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP): experimental design and forcing input data, Geosci. Model Dev., 9, 2701-2719, doi:10.5194/gmd-9-2701-2016.



Max-Planck Institute for Meteorology
Dr. Claudia Timmreck (PI)

Max-Planck Institute for Meteorology
Dr. Hauke Schmidt

University of Oslo
Prof. Dr. Kirstin Krüger

Disentangling the causes of the 1816 European year without a summer

2019 - Environmental Research Letters, Volume 14, Number 9

Schurer, A.P. | Hegerl, G.C., Luterbacher, J., Brönnimann, S., Cowan, T., Tett, S.F.B., Zanchettin, D., Timmreck, C.

Revisiting the Agung 1963 volcanic forcing – impact of one or two eruptions

2019 - Atmos. Chem. Phys., 19, 10379–10390,

Niemeier, U. | Timmreck, C., Krüger, K.

Disproportionately strong climate forcing from extratropical explosive volcanic eruptions

2019 - Nature Geosciencevolume 12, pages100–107

Toohey, M. | Krüger, K., Schmidt, H., Timmreck, C., Sigl, M., Stoffel, M., Wilson, R.

Clarifying the Relative Role of Forcing Uncertainties and Initial‐Condition Unknowns in Spreading the Climate Response to Volcanic Eruptions

2019 - Geophysical Research Letters

Zanchettin, D. | Timmreck, C., Toohey, M., Jungclaus, J., Bittner, M., Lorenz, S., Rubino, A.

The Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP): motivation and experimental design

2018 - Geosci. Model Dev., 11, 2581-2608

Claudia Timmreck | Graham W. Mann, Valentina Aquila, Rene Hommel, Lindsay A. Lee, Anja Schmidt, Christoph Brühl, Simon Carn, Mian Chin, Sandip S. Dhomse, Thomas Diehl, Jason M. English, Michael J. Mills, Ryan Neely, Jianxiong Sheng, Matthew Toohey, and Debra Weisenstein