The ongoing climate emergency has proved to be a far-reaching point of discussion in recent years, with the effects of rising temperatures, melting ice caps, changing seasons and more intense storms having the potential to affect aspects of our everyday lives across the globe. In the world of geohazards, the most discussed consequences are how changing weather patterns can influence landslides, slope stability and coastal erosion. But another potentially significant link, and in some cases the topic of intense debate, is that between climate variability and the triggering of volcanic activity.
One area of study where climate influence on volcanism is better understood and broadly accepted is that of glacial melting and the subsequent unloading of underlying magma chambers. Work done by Albino et al. (2010) looked at how surface load variations around Icelandic volcanoes act on their shallow magma chambers. Findings showed that in line with model predictions, the last nine historical eruptions at Katla volcano occurred during the summer season when snow cover was at its smallest. The 2004 Grímsvötn eruption was also noted to have been immediately preceded by a ‘jökulhlaup’, or glacial outburst flood, which may have triggered the event if the magmatic system was already close to failure. Another paper from Sigmundsson et al. (2010) supports these findings, stating that pressure can influence both magma production as well as the failure of magmatic systems and making the wider claim that a current reduction in ice load on subglacial volcanoes, due to climate change, is modifying pressure conditions in magmatic systems. More recent work by Praetorius et al. (2016) and Rawson et al. (2016) finds evidence for a similar link during deglacial transitions in Alaska and Chile respectively, suggesting this is not a phenomenon limited to certain geographies or volcanic settings. These findings suggest that not only are the failure conditions of magmatic systems altered by melting snow and ice, but an increased rate of magma production threatens more voluminous eruptive activity from subglacial volcanoes as well as potentially greater frequency.
Another potential link between the effects of a changing climate and volcanism comes in the form of sea level change at island arc volcanoes. A paper by Coussens et al. (2016) uses evidence in the rock record to find a connection between periods of rapid sea level rise and flank collapse at Soufrière Hills, Montserrat, and periods of heightened volcanic activity over the past million years. Satow et al. (2021) also identifies a link between sea level change and eruption frequency at Santorini, however these results show the opposite to Coussens et al. with periods of sea level fall triggering dyke injection and feeding eruption over the past 360,000 years. This could indicate that the effect sea level has on volcanism is dependent on geography or tectonic setting, but in either case the work shows that rapid sea level rise from climate change will have an effect on volcanoes around the world.
The relationship between volcanoes and our climate can work in both directions. Some climate change sceptics claim that volcanoes, rather than people, are responsible for current global warming trends. Looking back through history, we can see that the opposite is true. In addition to lava and ash, sulphur dioxide (SO2) is a major output from volcanic eruptions. If propelled high enough into the atmosphere in sufficient concentrations, this gas can reflect solar radiation and have a cooling effect on the Earth. There are records of these ‘volcanic winter’ events occurring throughout history, with a notable entry being the 1815 eruption of Mount Tambora resulting in the ‘year without a summer’ and credited as helping contribute to Mary Shelley’s writing of “Frankenstein”. Similarly, many historical records of famines can be linked to volcanic eruption events, such as the 1783 Laki eruption in Iceland. More recently, the eruption of Mount Pinatubo in 1991 caused ~15 million tons of SO2 to be propelled into the stratosphere, resulting in a 0.5°C drop in average global temperature for the next 2-3 years.
So could a potential increase in the frequency of eruptions, as a result of climate change, result in enough SO2 being released into the atmosphere to in fact cool the Earth and solve the problem? Although not impossible, this eventuality is extremely unlikely. There have been records showing periods of heightened volcanic activity triggering ‘little ice ages’ of regional cooling, but the size of eruptions needed to cause this are significant. For reference, the recent eruption of the submarine Hunga Tonga-Hunga Ha’apai volcano had effects felt across the globe (as discussed in our recent insight piece), but even this only produced a volcanic cloud containing ~50x less SO2 than the Mount Pinatubo eruption, and is reported to have had negligible effects on the climate.
An area where the links between climate variability and volcanism are somewhat less well-defined is regarding the influence of rainfall. A paper published in Nature by Farquharson & Amelung (2020) discusses the theory that anomalously high rainfall and a subsequent increase in pore pressure may have influenced the weakening and mechanical failure of the volcanic edifice at Kīlauea Volcano, Hawai‘i in 2018, contributing to the triggering of a subsequent eruption in May of that year. This connection raises an important question in the worlds of hazard and risk assessment; could more frequent intense rainfall events, driven by climate change, also influence the frequency of volcanic activity in a similar way to glacial melting and sea level change?
At this stage the answer seems to be that further study is required. Farquharson & Amelung’s findings are not universally accepted, and have been the subject of some fervent academic debate in recent years. Scientists at the USGS led by Dr. Mike Poland have responded to the article casting doubts on the links between rainfall and the 2018 Kīlauea eruption, questioning the rain gauge data used, the GPS measurements signaling pressurization of the magma chamber prior to eruption, and the significance of the relatively small pore pressure changes (~0.1 kPa) reported by Farquharson & Amelung. This in turn has been rebutted by the paper’s original authors in February 2022, responding to the questions raised and holding to their theory. They also point out in their response that the USGS themselves found links between anomalous rainfall and volcanic eruptions, discussed in a paper by Fred Klein (1984), but this was dismissed at the time because it was “difficult to imagine a physical triggering mechanism of rainfall on eruptions”. Other past work has been done in this area, including a paper by Barclay et al. (2005) linking increased rainfall to heightened probability of primary volcanic activity (pyroclastic flows, dome collapses and explosions) at Soufrière Hills Volcano, Montserrat between 1998 and 2003, and calling for integration of meteorological data into volcano monitoring.
The controversy surrounding this research suggests that more work will need to be undertaken, in order to determine how robust the links are between intense rainfall events and volcanic activity and their worldwide applicability. If evidence suggests that this is a global phenomenon, with high-quality data that reinforces the theories put forward and satisfies those with doubts, the implications would be profound. Not only would it mean that weather data and forecasts could provide another means of helping to predict volcanic hazards, but also that the continuing effects of climate change may mean activity such as dome explosions and flank collapses occur more frequently as intense rainfall occurs more often at active volcanoes. Another paper by Farquharson & Amelung (Preprint) widens the scope to examine what links between heavy rainfall and both eruptive and non-eruptive volcanic hazards may mean for subaerial volcanic regions globally in the face of rapid climate change. How this conversation develops will be of great interest, not only to those in the academic community, but also those involved with volcanic hazard assessment such as the WTW Research Network and its partners.
Overall, the links between climate and volcanism are definitive, but the how, when and where of climate change affecting the occurrence of volcanic activity is an area still under investigation. Even if claims that extreme rainfall can directly contribute to triggering of eruptions are considered unlikely, the combined findings of these papers prove that numerous aspects of climate variability have been seen to promote volcanic activity in the past, and that the continuing results of rapid climate change may have the potential to reshape the volcanic risk landscape around the globe.
An upcoming special issue in the Bulletin of Volcanology looks at progress made over the past twenty years and future challenges in the field, and includes a perspective paper by Aubry et al. discussing climate-volcano impacts. Given how this could affect those at risk from volcanic hazards, further exploration of these impacts is a potential focus point for the WTW Research Network in the future. Together with other teams in WTW such as the Climate & Resilience Hub, we have formed an Earth Risk Working Group to bring earth scientists, hazard analysts and stakeholders together and discuss what areas of research could most benefit everyone. The climate emergency is one issue at the top of our agenda, and these sort of links with other geohazards are an area we shall all be watching with great interest.
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Aubry, Thomas J.et al. “Impact of climate change on volcanic processes: current understanding and future challenges.” Perspective paper, special section of Bulletin of Volcanology "Looking Backwards and Forwards in Volcanology: Perspectives on the Trajectory of a Science." Accepted;
Barclay, Jenni, Jade E. Johnstone, and Adrian J. Matthews. "Meteorological monitoring of an active volcano: implications for eruption prediction." Journal of volcanology and geothermal research 150.4 (2006): 339-358.
Coussens, Maya, et al. "The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long‐term (> 1 Ma) record offshore Montserrat, Lesser Antilles." Geochemistry, Geophysics, Geosystems 17.7 (2016): 2591-2611.
Farquharson, Jamie I., and Falk Amelung. "Extreme rainfall triggered the 2018 rift eruption at Kīlauea Volcano." Nature 580.7804 (2020): 491-495.
Farquharson, Jamie I., and Falk Amelung. "Reply to: Rainfall an unlikely factor in Kīlauea’s 2018 rift eruption." Nature 602.7895 (2022): E11-E14.
Farquharson, Jamie I., and Falk Amelung. "Volcanic hazard exacerbated by future global warming–driven increase in heavy rainfall." Preprint (2021);
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