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.
A world warmed by four or more degrees
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.