Posted under Express 138
Profile: Bill McGuire
Here’s the volcanologist who says there’s evidence that “supports a robust link between changing climatic conditions and a broad portfolio of potentially hazardous geological and geomorphological processes”. Earthquakes, volcanic eruptions, tsunamis and landslides are some of the catastrophes that climate change and its rising sea levels and melting glaciers could bring. Skeptics are sure to point out that volcanoes have caused climate to change in the past and humans had nothing to do with it. Bill McGuire, author of Global Catastrophes begs to differ and thinks we have to change our ways, as well as our risk assessments.
Editor’s note: Bill McGuire has been speaking up on the linkage between geological events like earthquakes and climate change for some years. Since our mention in the last edition of Bill McGuire’s views, we have come up with more information (at the request of our readers), including his biographical details (who is this man!), an article in which he was quoted in Life Science in 2007, as well as a detailed paper put together by Bill McGuire for the Royal Society last year. – Ken Hickson
Bill McGuire is – by inclination and training – a volcanologist, and has worked on and visited volcanoes across the world. In 1996 he occupied a post of Senior Scientist at the Montserrat Volcano Observatory at a time of escalating activity and the first explosive eruption at the Soufriere Hills volcano. He currently holds the posts of Benfield Professor of Geophysical Hazards and Director of the Benfield Hazard Research Centre at University College London. The BHRC hosts over 50 core researchers and affiliates and is the largest academic hazard centre in Europe.
Bill’s principal research interests are volcano monitoring and volcanic hazards and global geophysical catastrophes and their impacts. He is also qualified to provide expert comment on a range of other natural hazards, including earthquakes, landslides, and the hazard implications of climate change. He is a staunch supporter of an anthropogenic cause for global warming and an evangelical advocate of the importance of drastic cuts in greenhouse gas emissions to mitigate a more climatically hazardous future.
Bill has been the UK’s representative of the International Association of Volcanology and Chemistry of the Earth’s Interior, Secretary of UK Panel of the International Union of Geodesy & Geophysics, and a Council Member of the Geological Society. He is a Fellow of the Geological Society and of the Royal Institution, and is a member of the Royal Institution’s Science Media Panel. Bill was also a member of the UK Government’s Natural Hazard Working Group, established by Prime Minister Tony Blair following the 2004 Indian Ocean tsunami.
Bill is author of over three hundred books articles and papers. His current academic work, the World Atlas of Natural Hazards was published by Hodder Arnold in August 2004 and his new popular science books, Surviving Armageddon: Solution for a Threatened Planet, and Global Catastrophes: a Very Short Introduction, were published by OUP in – respectively – June 2005 and January 2006. Bill is a member of the Association of British Sciences Writers and a regular contributor to radio, television, and the press on hazard-related matters. He presented the BBC Radio 4 series Disasters in Waiting and Scientists Under Pressure.
Global Warming Might Spur Earthquakes and Volcanoes
Andrea Thompson in Life Science (30 August 2007)
Earthquakes, volcanic eruptions, tsunamis and landslides are some of the additional catastrophes that climate change and its rising sea levels and melting glaciers could bring, a geologist says.
The impact of human-induced global warming on Earth’s ice and oceans is already noticeable: Greenland’s glaciers are melting at an increasing rate, and sea level rose by a little more than half a foot (0.17 meters) globally in the 20th century, according to the Intergovernmental Panel on Climate Change.
With these trends in ice cover and sea level only expected to continue and likely worsen if atmospheric carbon dioxide levels continue to rise, they could alter the stresses and forces fighting for balance in the ground under our feet—changes that are well-documented in studies of past climate change, but which are just beginning to be studied as possible consequences of the current state of global warming.
“Although they’ve described it in the past, nobody’s thought about it in terms of future effects of climate change,” said Bill McGuire of the University College London’s Hazard Research Center.
McGuire’s speculations of increased geological activity have not yet been published in a journal, but he has written an article about them published in the Guardian Unlimited.
One particular feature that can change the balance of forces in Earth’s crust is ice, in the form of glaciers and ice sheets that cover much of the area around Earth’s poles plus mountains at all latitudes. The weight of ice depresses the crust on which it sits.
As the ice melts, the crust below no longer has anything sitting on top of it, and so can rebound fairly rapidly (by geological standards). (This rebounding is actually occurring now as a result of the end of the last Ice Age: The retreat of massive ice sheets from the northern United States and Canada has allowed the crust in these areas to bounce back.)
Areas of rebounding crust could change the stresses acting on earthquake faults and volcanoes in the crust.
“In places like Iceland, for example, where you have the Eyjafjallajökull ice sheet, which wouldn’t survive [global warming], and you’ve got lots of volcanoes under that, the unloading effect can trigger eruptions,” McGuire said.
With the changing dynamics in the crust, faults could also be destabilized, which could bring a whole host of other problems.
“It’s not just the volcanoes. Obviously if you load and unload active faults, then you’re liable to trigger earthquakes,” McGuire told LiveScience, noting that there is ample evidence for this association in past climate change events.
“At the end of the last Ice Age, there was a great increase in seismicity along the margins of the ice sheets in Scandinavia and places like this, and that triggered these huge submarine landsides which generated tsunamis,” McGuire said. “So you’ve got the whole range of geological hazards there that can result from if we see this big catastrophic melting.”
Roland Burgmann, a geologist at the University of California, Berkeley, agrees that changes in ice cover can have significant effects on the underlying crust, but says that more research needs to be done to determine the actual scale of the threat and where the effects are most likely to occur.
Ice melt can have an added consequence because all that melted ice has to go somewhere—namely, the ocean.
And ice melt won’t be the only factor changing sea levels: as ocean temperatures rise, the water itself expands (a process called thermal expansion).
As all that extra water piles up, it could apply pressure to faults near coastlines.
“The added load of the water bends the crust, and that means that you tend to get tensional conditions in the upper part of the crust and compressional a bit lower down, just as if you bend a plank of wood or something,” McGuire explained.
These compressional forces could push out any magma lying around underneath a volcano, triggering an eruption. (This mechanism is actually believed to be the cause of the seasonal eruptions of Alaska’s Pavlof volcano, which erupts every winter when sea levels are higher.)
McGuire conducted a study that was published in the journal Nature in 1997 that looked at the connection between the change in the rate of sea level rise and volcanic activity in the Mediterranean for the past 80,000 years and found that when sea level rose quickly, more volcanic eruptions occurred, increasing by a whopping 300 percent.
If today’s worst-case global warming scenarios of catastrophic melting of glaciers and ice sheets come to pass, sea levels could rise rapidly, wreaking all sorts of geological havoc “comparable with the most rapid increases in sea level that we’ve seen in the last 15,000 years,” McGuire said.
Burgmann isn’t too worried about sea level rise causing more earthquakes or volcanic eruptions though, noting that catastrophic rates of sea level rise in the future are uncertain and that the current rate of rise—about 0.12 inches per year (3 millimeters per year)—isn’t enough to destabilize the crust.
“It would take a long time to add up to a significant amount,” Burgmann said—so while it’s an area of research to keep an eye on, it’s unlikely to have any disastrous consequences, at least for now.
For those wishing to read more, here is an account by Bill McGuire for the Royal Society on Climate forcing of geological and geomorphological hazards.
Bill McGuire of the Aon Benfield UCL Hazard Research Centre, Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
The 12 research papers and two summaries of conference discussion sessions contained in this Theme Issue build upon presentations and dialogue at the Third Johnston–Lavis Colloquium held at University College London in September 2009.
The meeting brought together delegates from the UK, Europe and the USA to address the issue of climate forcing of geological and geomorphological hazards, with a particular focus on examining the possibilities for a geospheric response to anthropogenic climate change. Papers included in this issue are a reflection of new research and critical reviews presented in sessions on: climates of the past and future; climate forcing of volcanism and volcanic activity; and climate as a driver of seismic, mass-movement and tsunami hazards. Two introductory papers set the scene.
In the first, McGuire summarizes evidence for periods of exceptional past climate change eliciting a dynamic response from the Earth’s crust, involving enhanced levels of potentially hazardous geological and geomorphological activity. The response, McGuire notes, is expressed through the triggering, adjustment or modulation of a range of crustal and surface processes, which include gas-hydrate destabilization, submarine and subaerial landslides, debris flows and glacial outburst floods, and volcanic and seismic activity.
Adopting a uniformitarian approach, and acknowledging potential differences in both rate and scale from the period of post-glacial warming, McGuire goes on to examine potential influences of anthropogenic climate change in relation to an array of geological and geomorphological hazards across an assortment of environmental settings. In a second and complementary review paper, Liggins et al. evaluate climate change projections from both global and regional climate models in the context of geological and geomorphological hazards.
The authors observe that, in assessing potential for a geospheric response, it seems prudent to consider that regional levels of warming at 2°C are unavoidable, with high-end projections associated with unmitigated emissions potentially leading to a global average temperature rise in excess of 4°C, and far greater warming in some regions. Importantly, they note that significant uncertainties exist, not only in relation to climate projections, but also with regards to links between climate change and geospheric responses. Using the format adopted by McGuire, Liggins et al. focus on high-latitude regions, global oceans, non-volcanic mountainous regions and volcanic landscapes.
The sensitivity to climate change of gas hydrates, in both marine and continental settings, has long captured interest, in relation to its potential role in past episodes of rapid warming, such as in the Palaeocene–Eocene thermal maximum (PETM), and in the context of anthropogenic warming. In the first of a pair of papers on the subject, Maslin et al. review the current state of the science as it relates to gas hydrates as a potential hazard. The authors note that gas hydrates may present a serious threat as the world warms, primarily through the release of large quantities of methane into the atmosphere, thus forcing accelerated warming, but also as a consequence of their possible role in promoting submarine slope failure and consequent tsunami generation.
Maslin and colleagues also stress, however, that, while the destabilization of gas hydrates in permafrost terrains can be robustly linked to projected temperature increases at high latitudes, it remains to be determined whether or not future ocean warming will lead to significant methane release from marine hydrates. In a second paper, Dunkley Jones et al. look back to the PETM, the most prominent, transient, global warming event during the Cenozoic, in order to evaluate the effects of the rapid release of thousands of gigatonnes of greenhouse gases on the planet’s climate, ocean–atmosphere chemistry and biota, for which the PETM perhaps provides the best available analogue. Dunkley Jones et al. support the view that, while gas-hydrate release was probably not responsible for an initial, rapid, CO2-driven warming, the as yet unknown event responsible for this subsequently triggered the large-scale dissociation of gas hydrates, which contributed to further warming as a positive feedback mechanism. As the authors note, this somewhat equivocal situation ensures that the question of what role, if any, gas hydrates may play in anthropogenic warming remains to be answered.
Continuing the gas-hydrate theme, Day and Maslin summarize—at the end of this issue—a discussion session at the colloquium, on the theme of Gas hydrates: a hazard for the 21st century? While wide-ranging, discussion focused primarily on the distribution of the potential hazard and how the level of hazard might vary with climate change. The outcome of the session was a ‘wish-list’ that emphasized the need for, among other things, a better understanding of whether and how (immediately versus over a longer time-scale) 21st-century climate change will trigger hydrate release, and a more robust appreciation of the likely fate of released methane.
Looking forward, one of the potential hazards presented by gas hydrates is their possible role in the destabilization of submarine slopes. This is one theme addressed by Tappin within a broader review of submarine mass failures (SMFs) as tsunami sources that incorporates the climate dimension. Tappin highlights the importance of climate in ‘preconditioning’ sediment so as to promote instability and failure, including its influence on sediment type, deposition rate and post-depositional modification. The author also notes that climate may play a role in triggering SMFs via earthquake or cyclic loading associated with tides or storm waves. Tappin makes the important point that, in the past, climate influence on SMFs appears to have been greatest at high latitudes and associated with glaciation–deglaciation cycles, which had a significant influence on sedimentation, preconditioning and triggering. As a corollary, Tappin notes that, as the Earth warms, increased understanding of the influence of climate will help to underpin forecasting of tsunami-sourcing SMFs, in particular at high latitudes where climate change is occurring most rapidly.
The theme of slope destabilization and failure, this time in a subaerial setting, is continued in a paper by Huggel et al., which examines recent large slope failures in the context of short-term, extreme warming events. Huggel and colleagues demonstrate a link between large slope failures in Alaska, New Zealand and the European Alps, and preceding, anomalously warm episodes. The authors present evidence supporting the view that triggering of large slope failures in temperature-sensitive high mountains is primarily a function of reduced slope strength due to increased production of meltwater from snow and ice and from rapid thaw processes. Looking ahead, they expect more frequent episodes of extreme temperature to result in a rise in the number of large slope failures in elevated terrain and warn of potentially serious consequences for mountain communities.
The slope failure hazard in mountainous terrain is also addressed by Keiler et al. in a paper that examines the influence of contemporary climate change on a broad spectrum of geomorphological hazards in the eastern European Alps, including landslides, rock falls, debris flows, avalanches and floods. In the context of the pan-continental 2003 heat wave and the 2005 central European floods, the authors demonstrate how physical processes and human activity are linked in climatically sensitive alpine regions that are prone to the effects of anthropogenic climate change. Importantly, Keiler et al. note that, while the European Alps, alongside other glaciated mountain ranges, are being disproportionately impacted upon by climate change, this is further exacerbated by regional factors, including local climatology and long-term decay of glaciers and permafrost. The authors conclude that future climate changes are likely to drive rises in the incidence of mountain hazards and, consequently, increase their impact on Alpine communities.
There is strong evidence for a crustal response to the rapidly changing post-glacial climate being elicited by load changes, either as a consequence of unloading at high latitudes and high altitudes due to ice-mass wastage, or as a result of the loading of ocean basins and continental margins in response to a 100 m or more rise in global sea level. The following three papers address the influence of load changes in the context of the triggering of seismicity and volcanism. In the first, Guillas et al. present the results of a statistical study of a putative correlation between contemporary variations in the El Niño–Southern Oscillation (ENSO) and the occurrence of earthquakes on the East Pacific Rise (EPR). The authors observe a significant (95% confidence interval) positive influence of the Southern Oscillation Index (SOI) on seismicity, and propose that increased seismicity on the EPR arises due to the reduced sea levels in the eastern Pacific that precede El Niño events, and which can be explained in terms of the reduction in ocean-bottom pressure over the EPR by a few kilopascals. Guillas et al. note that this provides an example of how variations in the atmosphere and hydrosphere can drive very small changes in environmental conditions that are able, in turn, to trigger a response from the Earth’s crust. Most importantly, they speculate that, in a warmer world, comparable and larger changes associated with ocean loading due to global sea level rise, or unloading associated with the passage of more intense storms, may trigger more significant earthquake activity at submarine fault systems that are in a critical state.
Continuing the theme, Hampel et al. take a broader look at how faults have responded to variations in ice and water volumes as a consequence of past climate change. Using numerical models, the authors demonstrate that climate-driven changes in ice and water volume are able to affect the slip evolution of both thrust and normal faults, with—in general—both the slip rate and the seismicity of a fault increasing with unloading and decreasing with loading. Adopting a case-study approach, Hampel and colleagues provide evidence for a widespread, post-glacial, seismic response on faults located beneath decaying ice sheets or glacial lakes. Looking ahead, the authors point to the implications of their results for ice-mass loss at high latitudes, and speculate that shrinkage of the Greenland and Antarctic ice sheets as a consequence of anthropogenic warming could result in a rise in the frequency of earthquakes in these regions.
In a similar vein, Sigmundsson et al. evaluate the influence of climate-driven ice loading and unloading on volcanism, focusing on Iceland and, in particular, on the Vatnajökull ice cap. Noting that a significant pulse of volcanism in Iceland, at the end of the last glaciation, flags a link between unloading and volcanism, the authors model the effects of contemporary ice-mass loss at Vatnajökull on future magmatic activity. Using a viscoelastic model of glacio-isostatic adjustment that incorporates melt generation in the underlying mantle, Sigmundsson and co-authors predict that ice wastage will result in additional magma generation beneath Iceland. The authors expect more frequent or more voluminous volcanic activity to be a consequence of enhanced melt generation, but also observe that it could take longer than decades or centuries for the resulting magma to reach the surface. Sigmundsson et al. also show that ice unloading is likely to drive shallow magma reservoirs progressively towards failure, although this effect will be small and therefore contribute only to modulating ‘normal’ activity.
A more general evaluation of the impact of a changing climate on glaciated volcanoes is undertaken by Tuffen, who looks ahead to how the melting of ice caps on active volcanoes may influence volcanic hazards in the 21st century. In reviewing the evidence for current melting of ice increasing the frequency or size of future eruptions, Tuffen notes that much remains to be understood in relation to ice loss and increased eruptive activity. In particular, uncertainty surrounds the sensitivity of volcanoes to small changes in ice thickness and how rapidly volcanic systems respond to deglaciation. Nonetheless, Tuffen expects an increase in explosive eruptions at glaciated volcanoes that experience significant ice thinning, and increased frequency of lateral collapse at glaciated strato-volcanoes in response to anthropogenic warming. On the positive side, deglaciation may ultimately reduce the threat from volcanic debris flows (lahars) and meltwater floods from volcanoes that currently support ice caps.
Volcano lateral collapse in response to a changing climate is explored further in the final research paper by Deeming et al., although in this case the driving force is precipitation rather than ice-mass loss. Deeming and co-workers present the results of a cosmic-ray exposure dating campaign at Mount Etna (Sicily), which constrains the timing and nature of collapse of the Valle del Bove, a major volcanic landslide scar on the eastern flank of the volcano. The authors link pluvial conditions during the early Holocene to the formation of a high-energy surface drainage system and to its truncation by a catastrophic lateral collapse event, ca7.5 ka BP, which opened the Valle del Bove. A possible mechanism is proposed, whereby magma emplacement into a water-saturated edifice caused the thermal pressurization of pore water, leading to a reduction in sliding resistance and subsequent large-scale slope failure. Deeming et al. present the mechanism as one possible driver of future lateral collapse at ice-capped volcanoes and at those located in regions predicted to experience enhanced precipitation.
Concluding the volcanoes and climate change theme, Tuffen and Betts draw together the thoughts of delegates at a second colloquium discussion session, which focused on Volcanism and climate: chicken and egg (or vice versa )? Among other outcomes of the discussion came the feeling that the title of the session was too prescriptive, with perhaps ‘Chicken and egg’ being more appropriate. This, it was broadly felt, better reflected the complexities apparent in the volcano–climate system, within which both climate forcing of volcanism and volcanic forcing of climate appear to play a part. Going further, rather than a chicken and egg debate, it was suggested that it might be more beneficial to concentrate efforts on understanding better how the volcano–climate system evolves over time, responds to different forcings, and incorporates various feedback mechanisms. Among other proposals, it was advocated that climate models should incorporate variable volcanic inputs so as to better explore how volcanic activity might affect the climate in the future.
Together, this set of papers provides a coherent whole that addresses a wide range of issues relating to how climate change may force geological and geomorphological phenomena capable of acting to increase natural hazard risk in a warmer world. They reflect a field of research that is only now becoming recognized as important in the context of the likely impacts and implications of anthropogenic climate change. We hope that this Theme Issue will provide a marker that reinforces the idea that anthropogenic climate change does not simply involve the atmosphere and hydrosphere, but can also elicit a response from the Earth’s crust and mantle. In this regard, we hope that it will encourage further research into those mechanisms by which climate change may drive potentially hazardous geological and geomorphological activity, and into the future ramifications for society and the economy.
One contribution of 15 to a Theme Issue ‘Climate forcing of geological and geomorphological hazards’.
© 2010 The Royal Society