ILULISSAT, Greenland -- Beyond the howl of sled dogs echoing across this hilly coastal village is the thunderclap of ancient icebergs splitting apart, a deafening rumble you feel in your bones.

There's no mistaking its big, loud, and powerful boom, a sound that can work up to a crescendo like rolling thunder. Or be as sudden as a shotgun blast.

Lifelong Greenland resident Karen Jessen Tannajik said people who live in Ilulissat -- an Inuit word for icebergs -- notice more about what's been calved by the village's nearby Sermeq Kujalleq glacier than sights and sounds.

"Right now, they're coming out so quick. There are not so many big ones, but many small ones," she said. "When I am tired, I can watch them and feel them and smell them. It seems like we get our power from them."

Sermeq Kujalleq is the largest glacier flowing out to sea in the northern hemisphere. The icebergs it calves float along a fjord that was recognized as one of the great wonders of the world when it was added to the World Heritage List in 2004 by the United Nations.

Although millions of people across the world still aren't convinced global warming is as big a problem as scientists claim, symptoms of the planet's warming pop up everywhere in Greenland.

The island's summer fishing season is longer. Crops are being grown in areas never thought possible for cultivation. Tourism is booming.

Even the island's first-ever craft brewery, Greenland Beer, is a product of global warming. The company markets the water it uses as purer than what is found in other parts of the world because it comes from melted inland ice formed thousands of years before the Industrial Revolution.

But Greenland's long-term problems from global warming will likely overshadow such short-term gains.

A lack of sea ice has made winter passage between settlements more difficult, if not impossible. That's a huge problem because there are no roads between villages. Greenland is one of the only places on Earth that relies on sled dogs as a primary mode of transportation.

Fishing is Greenland's No. 1 industry. Mild winters, especially north of Ilulissat in Uummannaq on Greenland's east coast, have made it treacherous for residents to fish or hunt on what little ice is left.

Greenland is the world's top producer of halibut and cold-water prawns. Halibut in particular have become more elusive, plunging to greater depths as the ocean temperature has warmed.

Two leaders of the Ilulissat fishing community, Peter Olsen and Johanne Mathaussen, said the downward movement of halibut makes those fish more difficult and costly to catch. Full-sized halibut that used to be available at depths of about 1,000 feet now swim at depths of about 2,600 feet.

Ove Rosbach, who has fished the Arctic for decades, blamed the decline on warmer ocean currents flowing to the north. He said a similar phenomenon occurred in the 1950s. Halibut returned when the ocean current cooled in the 1970s, but Mr. Rosbach said things feel different now.

"[Even] when the sun is not shining, it's still very warm," he said. "The sun is warmer than normal now."

To be fair, Greenland is a fickle place. A Danish territory of 56,000 people spread out across a land mass more than three times the size of Texas, it has gone through extreme warming and cooling periods before.

Literature produced for visitors claims various cultures of Inuits have lived on Greenland for more than 4,500 years, although it also notes extensive periods in which the island had no inhabitants -- usually when climatic conditions were so extremely cold there was little, if any, wildlife to hunt.

Changes to the Earth's climate are nothing new. Scientists believe natural climate variations occur every 100,000 years based on how the planet spins, tilts, and orbits around the sun.

The sun itself changes. NASA believes that volcanic eruptions on Earth, coupled with natural changes to the sun, explain warming and cooling from 1000 through 1850.

But the space agency also believes that Earth has been on a one-way warming trend triggered by human activity since the Industrial Revolution began about 1850.

Heat-trapping carbon dioxide, the chief greenhouse gas, is on a course to exceed 500 parts per million in the atmosphere later this century, something the human race has never experienced, said Daniel Schrag, director of Harvard University's Center for the Environment.

An abundance of greenhouse gases means higher temperatures on land and in the oceans. They rise in the atmosphere and trap the sun's energy, keeping heat from escaping back into space.

A climate variation of three to five degrees "is a really big deal," considering that much of the Earth was covered in ice 18,000 years ago when the planet was only an average of five degrees cooler, Mr. Schrag said. He believes that summer sea ice could be gone from the Arctic by 2015 -- well ahead of the earlier projection of 2050.

"We are performing an experiment at a planetary scale that hasn't been done for millions of years. No one knows exactly what will happen," he said.

The scientific consensus about climate change is based primarily around evidence of increasing air and ocean temperatures, accelerated melting of snow and ice at the polar ice caps, and rising ocean levels.

Records on global surface temperatures only go back to 1850, but the world's most prestigious body of climatologists -- the United Nations' Intergovernmental Panel on Climate Change -- noted in its landmark 2007 series of climate reports that the Earth's average temperatures for 11 of the 12 years from 1995 to 2006 were at or near record-high levels.

Those reports concluded there has been "unequivocal" warming of the planet and claimed with a certainty of greater than 90 percent that human activity was largely responsible. The data those reports used came, in part, from satellite images showing an accelerated loss of northern polar sea ice since 1978 and a rise in average sea levels since 1961 -- accelerating after 1993.

Ilulissat is Greenland's third-largest village, with 4,500 people and just as many sled dogs. Each summer, it hosts dozens of researchers and hundreds of tourists. Many of the latter see Greenland's famous Eqi glacier breaking off into seawater from the comfort of luxury cruise ships.

Nearly everyone who visits Ilulissat seems to have a feeling of suspended reality when they open their hotel blinds each morning. Almost without fail, the icebergs they saw the night before have been replaced by new ones.

How can such massive hunks of ice come and go so fast? After all, they were formed from thousands of years of compressed snow. And they look harder to budge than skyscrapers.

But it happens. The frequency that the Sermeq Kujalleq glacier calved icebergs over the past decade rose, throwing some of the world's top Greenland experts for a loop.

One of them is Swiss-born Konrad "Koni" Steffen of the University of Colorado. He has done field work in the Arctic since 1975 and on Greenland's ice sheet at least once every year since 1990. His work is cited in major publications, and he is at the table of most major climate talks.

Conventional wisdom during the 1970s was that Greenland's ice sheet would take thousands of years to melt. "Nobody would have predicted 10 to 15 years ago that Greenland would lose ice that fast," Mr. Steffen said. "That revises all of the textbooks."

His take-home message: Forget the scientific modeling. Greenland is melting faster than anyone's best guess.

"How can you have an ice sheet so big and respond that quickly?" he asked. "That is still part of the mystery, to be honest."

Ohio State's Jason Box is perhaps the most famous of Mr. Steffen's former students, having done research in Greenland every summer except one since 1994.

Mr. Box has likewise gained attention from the national media for his work. He synthesizes data he and others generate into a "holistic" view of Greenland's thaw, using a number of tools, including time-lapse photography.

Americans may fret about paying more for electricity if the next Congress enacts a carbon tax or strict regulations on utilities to combat global warming. But Mr. Box said that cost will be a fraction of what adapting to climate change will cost them years from now, especially if nothing's done to curb emissions now.

Billions of dollars will be needed to construct New Orleans-like levees along the nation's coastline to guard against flooding, he said.

"It's going to get too expensive for the U.S. to mitigate," Mr. Box said. "It's going to be kind of like taking on a global war against terrorism. It's going to be too expensive. It's going to sap the U.S. economy."

Sea level rise is "going to cost people whether their properties are flooded or not," he said.

On average, Greenland's ice sheet loses 300 billion tons of ice a year. That hasn't been enough to raise global sea level a millimeter a year, though.

The Greenland ice sheet has been eroding almost annually for 50 years, except for a short period in the 1970s when temperatures were cool enough in summer to keep it "in balance" by rejuvenating itself enough in winter. But the greatest ice losses on record are recent -- in 2003, 2005, and 2007, Mr. Box said.

In Alaska, coastal villages are eroding. Long stretches of highway are impassable for months at a time because they were built on permafrost that is melting.

One of the most heavily affected villages, Newtok (population 400), was told in June that it will get $3.3 million in state aid to help relocate displaced residents to higher ground.

Alaska is putting aside nearly $13 million to protect six remote villages in the coming year. That could be only the beginning of a massive tab for taxpayers. According to the Government Accountability Office, erosion and flooding affect 184 of Alaska's 213 native villages to some degree.

In Greenland, Ilulissat's soccer field is slumping because of permafrost melt. Tourists hiking marked trails to see the village's famous glacier feel the spongy soil.

"It's actually not a faith issue but whether or not you believe in the science. In its purest form [climate change] is objective science," Mr. Box said. "The ice in the Arctic is the canary in the coal mine. To put it bluntly, the canary is dead."