Global warming and volcanoes: game, set, match

April 16, 2010

Replying at Watt’s Up With That? to an article at the Scientific American web site claiming that the disappearance of glaciers due to global warming would lead to an increase in volcanic eruptions, geologist Steven Goddard provides a rebuttal and declares that theory to be bovine excrement:

The geothermal gradient of the earth is typically about 40°C per km, so a 0.5°C change in temperature is equivalent to a depth change of about 20 metres.  Near mid-ocean ridges this gradient is steeper, so the equivalent depth change in Iceland would be less than 20 metres.  Is it credible that a 0.5°C decrease in the melting point could stimulate excess volcanic activity?  Short answer – no. Volcanic activity is caused by magma rising to the surface, not glaciers melting.  However, the loss of the glaciers would reduce the amount of steam and ash generated.  Ash is formed when magma is cooled and fractured by steam.  So the loss of the glaciers would reduce the size of the steam/ash cloud and make the Iceland volcanoes behave more like Hawaii volcanoes.

In short, the loss of all ice in Iceland would make the volcanoes less destructive.

Read the whole thing for a good lesson in igneous petrology and volcanology.

UPDATE: More from Goddard, who explains that it’s not that climate change causes volcanoes, it’s that volcanoes can cause climate change.

Global warming, the disaster movie?

April 16, 2010

Why not? In addition to baking the Earth (except it’s getting cooler), raising the seas (except they’re not), and killing the polar bears (except they’re flourishing), global warming also causes volcanoes to erupt:

A thaw of Iceland’s ice caps in coming decades caused by climate change may trigger more volcanic eruptions by removing a vast weight and freeing magma from deep below ground, scientists said on Friday.

They said there was no sign that the current eruption from below the Eyjafjallajokull glacier that has paralysed flights over northern Europe was linked to global warming. The glacier is too small and light to affect local geology.

“Our work suggests that eventually there will be either somewhat larger eruptions or more frequent eruptions in Iceland in coming decades,” said Freysteinn Sigmundsson, a vulcanologist at the University of Iceland.

“Global warming melts ice and this can influence magmatic systems,” he told Reuters. The end of the Ice Age 10,000 years ago coincided with a surge in volcanic activity in Iceland, apparently because huge ice caps thinned and the land rose.

We believe the reduction of ice has not been important in triggering this latest eruption,” he said of Eyjafjallajokull. “The eruption is happening under a relatively small ice cap.”

In other words:

“Global warming isn’t in play here, but we’re taking this opportunity to scare you into agreeing to all the harebrained, economy-killing measures the UN, the IPCC, and delusional national governments can think up to deal with a problem that does not exist. Thank you.”

As a commenter at Watts Up With That? pointed out, if the magma chamber is so close to the surface as to be affected by a glacier, then it’s already itself melting the glacier, no CO2 needed.

Next thing you know, global warming will be blamed for stock-market crashes.

RELATED: In fact, undersea volcanoes may explain the calving of huge glaciers in the Antarctic peninsula, while the rest of the Antarctic ice sheet is expanding. It’s also a possible reason for the receding Arctic ice, though that’s expanded again in recent years. Again, no AGW bugbear required.

LINKS: More from the ever-restrained and temperate James Delingpole.