Greenland ice may melt much faster: U.N. scientist

By Gerard Wynn

LONDON (Reuters) - New research shows that man-made climate change could cause the Greenland ice sheet to break up in hundreds, rather than thousands, of years, the chair of a United Nations panel of scientists said on Monday.

Its entire collapse would raise sea-levels globally by around 7 meters (23 feet), they said.

The U.N. Intergovernmental Panel on Climate Change (IPCC) published its five-yearly report earlier this year, and described threats from global warming including sea-level rise of up to 79 centimeters this century.

It said that the entire Greenland ice sheet would melt over a period of thousands of years, if temperatures remained around 2 degrees centigrade (3.6 Fahrenheit) or more above the levels predating wholesale industrialization in the developed world.

But the new research, not considered by the IPCC, could change that view, according to Bert Metz, a senior IPCC member.

"No models that predict sea level rise include this," he told Reuters on the fringes of a climate change conference hosted by Chatham House in London on Monday.

"It's plausible that the whole thing could disintegrate in hundreds of years, an order of magnitude faster."

The new research shows rapid melting on the surface of the Greenland ice sheet. Meltwater is disappearing down huge crevasses, and theory suggests that water will lubricate the bottom of the ice sheet and speed up its flow into the sea.

"They have seen more movement at the edges," said Metz.

"It needs to be challenged... but some scientists are clear and say this is it. The IPCC always tries to be cautious."

Metz is the co-chair of the third of the IPCC's three reports published this year, focusing on the policy options to fight the global warming problem.

One option is to penalize emissions of planet-warming carbon dioxide (CO2), for example, through a carbon tax. To make a significant difference, carbon prices should reach $50 to a $100 per tonne of avoided CO2 emissions by 2030, he said.

Carbon prices on a European trading scheme are currently around 20 euros ($26.92) per tonne.

Metz underlined the scale of the problem in trying to establish control over greenhouse gas emissions within 10 years, the most ambitious target his report considered.

"It's a huge challenge to turn around the supertanker of global emissions within 10 years. Many would say it's impossible," he told the conference. "I'm not saying that yet."