There is growing evidence that melting ice sheets and sea level changes can trigger earthquakes (NOTE: Subscribers can still listen to this show) and volcanic eruptions.
Most of the evidence for the climate's influence on geology comes from the end of the last ice age, around 12,000 years ago, when ice sheets retreated from much of the planet, at the same time that a sudden outburst of geological activity occurred. Geologist Bill McGuire thinks that the weight of ice maintains high pressures underground that keep magma at the root of volcanoes solid and suppress eruptions. But as the ice melts, the huge weight is released and the land surface lifts, reducing the pressure below.
And many geological fault lines are on a knife-edge, waiting any nudge to send their seismic mayhem to the surface. He warns that we need to watch out as the world starts to warm once more.
On the Environment 360 website, Fred Pearce quotes McGuire as saying, "Volcanoes can be incredibly sensitive to tiny changes to their external environment, constantly teetering on the edge of stability."
Pearce writes: "Nobody should want climate scientists to rush around the world warning of geological Armageddon. Too much remains unknown. Caution certainly is justified. But the danger is that a topic of potentially huge importance ends up being ignored. And the research needed to substantiate--or to repudiate--these concerns is never done. That would be unwise."