Could a changing climate set off volcanoes and quakes?

Some researchers are unconvinced by all this. When the journal Nature published a short report on McGuire's Royal Society meeting, the first anonymous online comment began: "This has to rank as one of the most preposterous warming scare articles of the new century."

None of the climate scientists I contacted felt competent to comment on McGuire's ideas. But some geologists have expressed skepticism about any immediate cause for concern. Roland Burgmann of the University of California, Berkeley did not want to add to a statement he made five years ago that "it would take a long time" for sea level rise to trigger seismic activity.

McGuire is keen to underline that his message "is not intended as a speculative rant." He is simply reviewing the voluminous literature already in the public and peer-reviewed domains. He makes a point of dismissing talk that climate change might have caused the Sumatra earthquake that triggered devastating Indian Ocean tsunami in 2004 as "clearly nonsense." But he insists that "people who find the idea [of climate change triggering geological events] flaky don't appreciate that the link between abrupt climate change and a response from the solid Earth is supported by huge amounts of research."

So how scared should we be? The short answer is nobody knows. While clearly some geological responses to surface events could occur fast, others could take thousands of years to emerge.

One place we might expect trouble is Iceland, the scene of the eruption of Eyjafjallajökull two years ago. Its smoke billowing across flight paths grounded transatlantic flights for a week. Nobody is blaming that eruption on climate change, but the island's ice cap has been thinning for more than a century now. In response, the land surface is rising, often by more than 20 millimeters a year. This is still an order of magnitude less than the rates at the end of the last ice age, but Sigmundsson says it nonetheless creates "highly significant" pressure release - and new magma ready for ejection.

There are other dormant volcanoes and quiescent fault-lines lurking beneath the thick ice caps over Greenland and Antarctica. Andrea Hampel, a geologist at Leibniz University in Hanover, Germany, warns that the subdued geology in both places today is likely caused by the presence of large ice sheets. "Shrinkage [of the ice] owing to global warming may ultimately lead to an increase in earthquake frequency in these regions," she predicted in a paper published two years ago. "This effect may be important even on timescales of 10 to 100 years."

Tuffen, of the University of Lancaster, agrees. He points out that the West Antarctic Ice Sheet is set to thin by 150 meters by 2100, potentially waking dormant volcanoes. Other volcanoes in the firing line, he says, could include Nevado del Ruiz in Colombia and Cotopaxi near Quito, the capital of Ecuador.

We could already be seeing a resurgence of earthquakes. McGuire admits there is no certainty about any link, but he points out that there has been "an unprecedented cluster of massive earthquakes" in recent years. Since 1900, the world has been struck by seven "super-quakes," with a magnitude exceeding 8.8. While only one of them occurred in the first half of the 20th century, three more came in the second half, and there have been three more in the past seven years, bringing death and destruction to Sumatra, Chile, and Japan.

The world of climate science has so far largely failed to acknowledge these new potential hazards from climate change. There is no mention of them in the Intergovernmental Panel on Climate Change's last science assessment in 2007.

A special report of the Intergovernmental Panel on Climate Change (IPCC) on extreme climate events, published in April, restricts its comments on McGuire's ideas to a single paragraph. While conceding that crust movements resulting from melting ice "may result in an increase in earthquake activity, perhaps on timescales as short as 10 to 200 years," it concludes that "there is low confidence in the nature of recent and projected future seismic responses to anthropogenic climate change." McGuire says it is not yet clear if quakes, tsunamis and volcanoes will be addressed in the next full scientific assessment, due in 2014.

Why this reticence? McGuire concludes that climate scientists at the IPCC have blind spots, both about geology and about learning the history of what happened during past eras of climate change. The science of geological responses at the end of the last glaciation, he says, "is extremely well established." Nonetheless, the implications for the future remain largely ignored even among the most strident campaigners for action on climate change.

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.