Nineteenth-century explorer Fridtjof Nansen called the Arctic "nature's great ice temple," a place teeming with roaming polar bears and a forbidding landscape frozen since "the earliest dawn of time."

But today, one cannot venture far enough north to escape global warming. The region has heated up nearly twice as fast as the rest of the globe over the past 50 years, according to a 2004 study assessing climate change in the Arctic. Land-based ice such as glaciers, ice sheets and permafrost and floating ice are vanishing, and the ongoing thaw has profound ramifications for the rest of the world.

Arctic powers the "heat pump"

The Arctic is critical to the globe's climate and influence temperatures everywhere. 

It sounds counter-intuitive, but the Arctic plays a primary role in distributing heat around the world through what is known as the "heat pump." The ocean's currents circulate heat throughout the world, through a system known as the "great conveyor belt." Two main forces keep the conveyor moving: winds and ocean density differences. The Arctic is key to the density differences.

The conveyor belt's critical points are where surface waters plunge into deep waters. This happens only in a few places, two of which are in the North Atlantic. As the ocean surface waters cool in the far north, they become denser and sink toward the bottom of the ocean. There, the cold water flows toward the equator. This combination of sinking and flow help drive the ocean conveyor.

Because the cold waters that flow south must be replaced, warm surface currents flow farther north and deliver warmth to places far north. Without the ocean conveyor's heat pump, Europe's temperate climate would be much colder.

Global warming is changing that key spot in the North Atlantic where the surface waters plunge. A mix of increased precipitation, river run-off and melting ice—all related to climate change—is making surface waters in the north less salty and dense, weakening a major pump in the ocean's natural circulation. (More about the oceans and global warming.)

Arctic melt is speeding up warming

The loss of Arctic ice is also speeding up the Earth's warming because of its reflective properties. Ice acts like a mirror, bouncing sunlight back toward space and preventing the sunlight from heating the surface. Winds carry the cooler air down from Canada into the U.S., cooling our climate.

Open water and bare soil are not as bright as ice and snow, so they absorb heat instead of reflecting it. When ice melts, the darker surfaces are exposed and absorb more solar energy. This extra heat melts even more ice, which in turn exposes even more dark surfaces. This is what scientists call a positive feedback loop. Once the loop gets going, it tends to keep going—and to speed up. Less ice means less cooling much faster. Or, as the American Meteorological Society's senior scientist Susan Joy Hassol put it to U.S. senators in a committee hearing in 2004: "What we're looking at is having a less efficient air conditioner."

Loss of Arctic ice is not just speculation—it's already happening. 2003 brought a dramatic example of Arctic ice disappearing. The Ward Hunt Ice Shelf, the largest in the Arctic, broke in two, draining a unique freshwater lake that was home to a rare microbial ecosystem. Since the 1970s, 400,000 square miles of Arctic sea ice has disappeared. That's the size of Texas and California combined. (IPCC Third Assessment report) Even worse, the years 2002 through 2005 have all seen record or near-record low ice cover.

What this means for the rest of us

While the Arctic melt has profound effects on the region's people and ecosystems, it also spells trouble for the rest of the world. For instance, the changes to the ocean's circulation system mean that though some places will get much warmer, other places, such as Europe, which won't get the warmth from the Gulf Stream, will get much cooler.

One of the Arctic thaw's most profound effects on the world beyond the Arctic is sea-level rise. When glaciers melt and spill into the ocean, they raise sea levels around the globe. The booming cities and counties along the East and West coasts house half of the U.S. population and are among the communities that will be most threatened by melting ice.

Currently, the retreat of the world's glaciers is adding enormous amounts of fresh water to the ocean. Between 1961 and 1997, for instance, about 890 cubic miles of ice has been lost. That means that melting glacier ice has added approximately 980 trillion (or 979,994,261,211,428.5) gallons of water to the oceans. That would be like dumping more than a million Olympic-sized swimming pools into our oceans.

Some studies have even suggested the possibility that warming over the next several centuries would lead to the complete, irreversible disappearance of the Greenland ice sheet. Were that to occur, sea levels would rise an extra 23 feet. (More about the dangers of rising sea levels.)

"If we ignore the Arctic's warning—and it is warming—the polar bears and native Alaskans won't be the only ones who suffer," notes Environmental Defense scientist Dr. Bill Chameides. "Our children and grandchildren could pay a hefty price."