One worried bear - an apt symbol of the grim news from the planet's twin sentinels (global warming)

One worried bear - an apt symbol of the grim news from the planet's twin sentinels By Roger Highfield, Science Editor (Filed: 30/09/2005)

The white wastes at the Poles are often called the planet's sentinels; they provide an early warning system that will reveal what is in store for the rest of the world.

For decades, scientists have predicted that if the effects of global warming took hold, they would first be measurable at the frozen extremes, where the impacts would be felt with a rapidity and intensity unlike anywhere else.

The reason the Poles are a litmus of climate change is simple: when ice melts, the surface of the water or the land that lies beneath is darker and accumulates even more heat from the Sun, an example of "positive feedback" that alters local climate and accelerates global warming.

On Wednesday, American scientists said new satellite data revealed a dramatic retreat of sea ice in the Arctic, marking the fourth consecutive year that there has been a stunning shrinkage in sea ice at the close of the northern summer.

It is not quite true to say that the north polar ice cap will be gone within a century. But by then it is likely that all the sea ice will have melted away, at least in the summertime, leaving the North Pole all at sea and the last remnant of the once-vast northern ice sheets slowly wasting away on Greenland.

Why? Although the world has seen a dramatic rise in carbon dioxide levels in the past century, driven by the burning of oil and gas, the links between this, global warming, and changing ice and rising sea levels are complicated.

The changes in Antarctica appear mixed compared with those in the Arctic: icebergs have broken off and ice shelves have disintegrated but the world's largest ice sheet, the east Antarctic ice sheet, is growing.

However, this is still consistent with global warming: increased snowfall is one consequence of a warmer planet with a moister atmosphere and wetter climate.

The effects of polar changes on sea level depend on what kind of ice we are talking about: the ice that floats in the oceans, and the ice that sits on land. Arctic retreats have been seen in sea ice that is relatively thin - up to a few metres thick.

Even though this icy crust is melting, this will have no direct effect on sea levels, just as Archimedes would have predicted: this is the same reason that melting ice cubes leave the level of a drink unchanged.

However, this process influences regional temperature and the circulation of ocean currents, and consequently the Earth's climate.

In contrast, the ice sheets that blanket Antarctica and Greenland are miles thick. It is the growth and shrinkage of these ice masses that have a direct influence on sea level, complicated by the thermal expansion of the oceans and changes in the volume of water stored on land.

Recent polar changes have been so rapid that, even if the causes are entirely natural, we need to monitor and understand them, said Prof Chris Rapley, the director of the British Antarctic Survey.

"Stronger warming in the polar regions is a prediction of models of climate change and, lo and behold, there it is.

"We are seeing the Antarctic peninsula heating up dramatically, along with Alaska and parts of Siberia.

Given the recent run of hotter summers and more powerful typhoons, the likelihood that climate change is man-made is becoming ever harder to dispute.

A new quest to firm up the link will be launched next week with the European Space Agency's Cryosat mission.

From an altitude of around 430 miles, the mission will provide conclusive evidence of rates at which ice cover is shrinking, thanks to technology conceived in Britain, a sophisticated radar instrument called SIRAL.

To measure the thickness of a given ice layer, Cryosat's radar altimeter satellite sends out a signal and records its return. Because the edge of an ice sheet can be uneven, it is often difficult to catch the reflected signal, or know precisely where it came from.

However, Cryosat overcomes this by using a clever double-antenna design and will, for the first time, reveal changes at the very point where it is most significant: at the ice edge.

Perhaps the biggest mystery of all, according to Prof Rapley, is why the public does not seem as animated about the threat of climate change as was the case with nuclear bombs at the height of the Cold War.

The mushroom cloud was the icon of the atomic age and it could be that the world needs a more immediate symbol of climate change.

Perhaps, he said, the fall-out of climate change could provide one depressing icon: one of the planet's most charismatic species, the polar bear, is increasingly threatened by the big melt.

Worst fears confirmed as mother walks on thin ice By Nic Fleming, Science Correspondent (Filed: 30/09/2005)

A glimpse of a mother polar bear and her cub walking along a pressure ridge just three miles from the geographical North Pole in April 2000 concerned Pen Hadow in more ways than one.

Packing up his tent at the end of an expedition to the Pole, the explorer knew he would have to be aware of the immediate dangers the bear could pose until he and the client he was guiding were safely onboard the Russian helicopter due to take them home.

However the sighting also worried him because in his experience bears did not venture so far north with their young because the thickness of the ice should have prevented the presence of seals, their main food source.

Mr Hadow, 43, first travelled to the Arctic in 1994 and has returned most years since, achieving his goal of reaching the North Pole solo and unaided in 2003.

Yesterday he said: "The sight of a mother and her young first year cub just three miles from the northern geographic pole was by my understanding a very unusual sighting.

"Seals are not present in any useful number where there are insufficient waterways for them to come up to breathe.

"Therefore if a mother bear feels it is safe to take her cubs so far north the implication is there are more waterways.

"We should not mistake such anecdotal evidence for hard, scientific evidence of climate change, but for me it was one example of a biological indicator of the thinning of the Arctic ice cap."

To be able to claim to have walked to the North Pole, explorers set off from the northern-most beaches of Canada or Russia.

However, over the past 15 years or so, those making attempts from Russia have often found the ice too thin or non-existent.

This affected Mr Hadow in 2001 when he was again guiding a private client who wanted to make the trip to the Pole from Russia.

"The idea was to go unsupported with all our supplies. However, when we got there we found the first 20 miles was a mixture of open water or dangerously thin ice.

"Traditionally the temperatures were so low that when the wind blew the ice offshore, more water would freeze within hours.

"But as the temperatures have got milder this has not been happening, leaving more waterways, thinner ice or just open water for up to 50 miles. I'd say this has become a substantial issue since 1998."

Another piece of anecdotal evidence is the recent increasing use by commercial shipping vessels of the northern sea route, also known as the north-east passage, from the Pacific Ocean through the Baring Strait and along the northern coast of Russia.

Mr Hadow said: "I used to say that my grandmother's generation went from the use of horse-drawn carts to man walking on the moon.

"Our children are going to experience the vanishing of the Arctic ice cap. This is a major feature that you, I and your readers have been brought up to view as a central feature of our planet.

"Since the 1960s we have lost around 30 per cent of the thickness of the Arctic ice cap. In recent years the northern sea route has become a viable commercial sea route. In the summer ships are regularly making the trip without ice-breakers. At the moment the Arctic ice cap is a huge reflective lid.

"The snow and ice reflect around 85 per cent of the solar radiation that hits it. If you take this lid off, only about 15 per cent of the solar radiation will be reflected, so that energy will be absorbed into the oceans which will lead to major changes to our weather systems."

Mr Hadow added that within 50 years, the thinning of the ice could lead to a north-west passage route from the Atlantic Ocean to the Pacific Ocean through the Arctic archipelago of Canada also becoming viable for commercial shipping.

Damn it! I was hoping global warming would rid us of New York once and for all!

I guess this means that all the carping about rising sea levels was BS all along, huh? So then "Water World" was just a movie, not a prophecy? Obviously the editors didn't catch this little crack in the "global warming" mythology.

The other part that makes no sense that has been appearing in the pseudo-science of global warming lately, is that with the polar ice caps melting, they create a darker surface area that enhances global warming even more. That said, how did we get polar ice caps in the first place? These guys continually paint themselves into a corner with these creative lies, but they're never made to answer for them.

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