The polar ice sheets of Antarctica and Greenland are now melting three times faster than in the 1990s, according to a study released Thursday and co-authored by a Boulder scientist.

To date, it is believed that ice-sheet melt has only added about half an inch to rising sea levels. But the quicker pace of melting, particularly in Greenland, now has ice scientists worried.

New research published in the journal Science concludes that Antarctica is melting, but points to the smaller ice sheet in Greenland, which covers most of the island, as the more critical issue. Its melt rate has grown from about 55 billion tons a year in the 1990s to almost 290 billion tons a year recently, according to the study.

"Greenland is really taking off," said the study's co-author Ted Scambos, lead scientist at Boulder's National Snow and Ice Data Center, which is part of the University of Colorado.

"In Greenland, the melt was so severe that it took away the very instruments we used to measure the ice sheet," Scambos added. "Many instruments were melted out and toppled over because melt proceeded to a level we have never seen before."

The work of the NSIDC also made waves Thursday on the other side of the world. It was reported at the U.N. climate talks in the Qatari capital of Doha that, based on data supplied by Boulder researchers, an area of Arctic sea ice larger than the United States melted this year.

The dramatic record-low reading of Arctic sea ice documented in the U.N. report prompted the World Meteorological Organization to declare climate change is happening "before our eyes."

Arctic ice melt was one of numerous record-breaking weather events to hit the planet in 2012, but the ice melt dominated the yearly climate report, with the U.N. concluding ice cover had reached "a new record low" in the area around the North Pole.

The loss of ice measured during the warming months of March to September was a staggering 4.57 million square miles -- an area bigger than the U.S.

WMO Secretary-General Michel Jarraud said, "The alarming rate of its melt this year highlighted the far-reaching changes taking place on Earth's oceans and biosphere."

"Climate change is taking place before our eyes and will continue to do so as a result of the concentrations of greenhouse gases in the atmosphere, which ... again reached new records."

According to Mark Serreze, director of CU's NSIDC, "The decline of sea ice seems to have accelerated over the past. It has just gotten faster. The year of 2007, we were all astounded; there was all kinds of talk about what was happening. But in 2012, we didn't just beat -- we blew out the old record.

"From where we're looking now, we don't see any evidence that this trend is going to stop," Serreze added. "My view is we could be looking at an Arctic Ocean with no sea ice in summer by 2030, or 20 or 30 years from now."

Representing Boulder's NSIDC in Doha is scientist Ken Schaefer, whose area of specialty is permafrost carbon cycle feedback.

As Serreze explained, there is a great quantity of carbon locked up in the permafrost -- frozen soil. As thawing of the permafrost occurs, he said, microbes that have been freed become active in the atmosphere.

"Respiration ensues, and they breathe out carbon -- mostly as carbon dioxide, but also as methane," Serreze said.

"Then, that adds to the atmosphere's existing load of greenhouse gases, makes it even warmer and thaws even more of the permafrost, and gives an even bigger carbon release. There is a concern out there that this could become a significant player" in climate change. "Once the genie is out of the bottle, you can't put it back in."

As for the sea ice, because of the size of the world's oceans, it takes a lot of ice melting -- about 10 trillion tons -- to raise sea levels by 1 inch. Since 1992, ice sheets at the poles have lost nearly 5 trillion tons of ice, according to researchers, raising sea levels by about a half inch.

Even that seemingly small amount likely worsened flooding from an already devastating Hurricane Sandy last month, said NASA ice scientist Erik Ivins, another co-author of the study concerning the Antarctic and Greenland ice sheets.

"The more energy there is in a wave, the further the water can get inland," Ivins said.

Scientists blame man-made global warming for the melting. Burning fossil fuels, such as coal and oil, emits carbon dioxide and other greenhouse gases that trap heat, warming the atmosphere and oceans. Gradually, that erodes the ice sheets from above and below. Snowfall replenishes the ice sheets but hasn't kept pace with the melting.

Just how much ice is vanishing at the two poles has been difficult for scientists to answer. In 2007, the Intergovernmental Panel on Climate Change did not include ice sheet melt in its calculations of future sea level rise because numbers were so uncertain.

Scambos said the study he co-authored involved more than 50 scientists working to reconcile three different methods of measuring ice sheet loss. Their work leaves him optimistic that ice-sheet melt's contribution to rising sea levels can soon be quantified with greater confidence -- most likely in a 2014 report by the IPCC.

The Associated Press contributed to this report.

Contact Camera Staff Writer Charlie Brennan at 303-473-1327 or brennanc@dailycamera.com.