The Arctic ice cap will become open water by the middle of this century, according to predictions by the Met Office's Hadley Centre for climate prediction. To watch an animation of the shrinking ice, click here.

As the politiicans in Bali debate how to deal with climate change, scientists on the other side of the world were reporting ever more devastating impacts from global warming.

The American Geophysical Union's annual meeting, in San Francisco, is one of the largest scientific conferences in the world - and it coincides exactly with the second half of the Bali meeting.

There, in a series of symposia, climate scientists reported how 2007 was becoming a "year of worsts". So far the year has seen the least sea ice in the Arctic, fastest retreat of mountain glaciers on Kilimanjaro, and the quickest decline of snow in Greenland.

BACKGROUND

• UN chief to return to Bali climate talks

• Al Gore: free of diplomatic niceties

• Al Gore lambasts US climate obstructions

• Scorching decade claims eight hottest years

2007: worst year for the environment

As UN climate talks go down to the wire, scientists across the world says 2007 was a 'year of worsts' for the planet

• This decade breaks records in table of world's hottest years

BACKGROUND

• US rejects Bali climate change guidelines

• UN chief: act now on climate or face oblivion

• Al Gore calls for climate ‘mobilisation’

• Carbon emissions are 'higher than claimed'

• A convenient £50m for green Gore

Multimedia

• Video: protests in Bali

• Video: Going green with God

• The environment - 2007 in pictures

BACKGROUND

• Carbon stand-off puts climate talks at risk

• US 'must change lifestyle' for planet's sake

• Woodman, spare that high-carbon tree

• Act now or prepare for disaster

US laws will sap Europe’s energy

There is a serious danger that the politics of the American cornfield are again threatening trade and development

BACKGROUND

• Water shortages 'likely trigger for wars'

• Global crisis reveals big cracks in policies

• UN climate circus rolls in on CO2 cloud

• Carbon Trust not meeting the challenge

We’re not doomed yet

Should we really be listening to the views of one man just because they are eye-catchingly more dramatic than the consensus?

BACKGROUND

• Brown’s bid to seal fate of carrier bags

• Opec ponders wealth of alternatives

• Climate change panel verdict: the future is bleak

• A global warning for UN chief

Related Links

• This decade set to be hottest on record

Some even wondered if the earth is now nearing a "tipping point" in which climate change will become irreversible, sliding humanity into a future of floods, heat, and rising sea levels.

Some of the most dramatic changes occurred in the Arctic. At the ice pack's minimum extent last September, it was 23 per cent smaller than anytime since measurements began, with 1.6 million square kilometers more open water than in the previous record melt of 2005.

Water and air temperatures also exceeded previous maximums. "We have a consistent picture that we've really moved into record territory in the past four or five years," said John D. Walsh, Professor of Global Climate Change at the International Arctic Research Center for the University of Alaska, Fairbanks.

Greenland was the same, with snow melting over a greater fraction of the island than ever before. And it wasn't just a matter of one or two hot days.

"In some places, melting occurred for 25 or 30 days longer than average," said Marco Tedesco an assistant research scientist at the University of Maryland Baltimore County's Joint Center for Earth Systems Technology, and NASA-Goddard Space Flight Center . Since 1988, he added, the thawing zone has expanded, on average, by 19,000 square kilometers a year – an area nearly the size of Wales .

The cause is still under investigation, but one factor appears to have been an extended patch of sunny, dry weather that settled across much of the Arctic Ocean north of Canada. "These weather patterns could be the trigger that opened up the blinds, letting the sunlight in," said Graeme L. Stephens, University Distinguished Professor in the Department of Atmospheric Science at Colorado State University .

Once the melt set in, it produced conditions that set the stage for even-faster melting. In Greenland, for example, this winter's new snow will overlie a zone of older snow, melted and refrozen. That snow is darker than the fresh snow and lies ready and waiting to warm up quickly when next year's sunlight melt off the winter's powder.

The result: many scientists believe the Arctic Ocean has reached a "tipping point" in which nothing but deep and sustained global cooling could reverse the rapid trend toward diminishing summer ice. "Everything is working in consort toward a bluer or totally blue Arctic Ocean ," said Josefino Comiso, senior research scientist for polar oceanography at NASA-Goddard Space Flight Center.

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