Abstract
AbstractMajor tropical volcanic eruptions have a large impact on climate, but there have only been three major eruptions during the recent relatively well‐observed period. Models are therefore an important tool to understand and predict the impacts of an eruption. This study uses five state‐of‐the‐art decadal prediction systems that have been initialized with the observed state before volcanic aerosols are introduced. The impact of the volcanic aerosols is found by subtracting the results of a reference experiment where the volcanic aerosols are omitted. We look for the robust impact across models and volcanoes by combining all the experiments, which helps reveal a signal even if it is weak in the models. The models used in this study simulate realistic levels of warming in the stratosphere, but zonal winds are weaker than the observations. As a consequence, models can produce a pattern similar to the North Atlantic Oscillation in the first winter following the eruption, but the response and impact on surface temperatures are weaker than in observations. Reproducing the pattern, but not the amplitude, may be related to a known model error. There are also impacts in the Pacific and Atlantic Oceans. This work contributes toward improving the interpretation of decadal predictions in the case of a future large tropical volcanic eruption.
Highlights
Volcanoes have global impacts on climate from monthly to centennial timescales (Ding et al, 2014; Robock, 2000; Timmreck, 2012; Timmreck et al, 2016; Zhong et al, 2011)
In the analysis that follows, we consider the surface and zonal-mean responses first, after which we focus on the large climate modes, North Atlantic Oscillation (NAO), El Niño–Southern Oscillation (ENSO), and Atlantic Meridional Overturning Circulation (AMOC), as other impacts can often be derived from them (Clark et al, 2017)
Impact on the North Atlantic Ocean To explore the potential longer-term climate response, we look at the North Atlantic Ocean, a region where volcanoes can induce
Summary
Volcanoes have global impacts on climate from monthly to centennial timescales (Ding et al, 2014; Robock, 2000; Timmreck, 2012; Timmreck et al, 2016; Zhong et al, 2011). Volcanic impacts are needed to fully explain the climate variability of the twentieth century (Smith et al, 2016). The Atlantic Meridional Overturning Circulation (AMOC) increases in strength and leads to regional warming (Iwi et al, 2012; Ottera et al, 2010; Stenchikov et al, 2009; Swingedouw et al, 2017). The problem may be further exacerbated by models having a smaller signal than the real world, especially in the North Atlantic, so very large ensembles (more than a 100 members) are likely necessary to capture a response (Baker et al, 2018; Dunstone et al, 2016; Scaife & Smith, 2018). We use experiments that have been run to show the impact of volcanic aerosols in the context of climate predictions and are designed to reduce model biases. In the analysis that follows, we consider the surface and zonal-mean responses first, after which we focus on the large climate modes, NAO, ENSO, and AMOC, as other impacts can often be derived from them (Clark et al, 2017)
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