Climate forcing of geological and geomorphological hazards.

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 highend 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.