Global warming 'past the point of no return'

A record loss of sea ice in the Arctic this summer has convinced scientists that the northern hemisphere may have crossed a critical threshold beyond which the climate may never recover. Scientists fear that the Arctic has now entered an irreversible phase of warming which will accelerate the loss of the polar sea ice that has helped to keep the climate stable for thousands of years.

They believe global warming is melting Arctic ice so rapidly that the region is beginning to absorb more heat from the sun, causing the ice to melt still further and so reinforcing a vicious cycle of melting and heating.

The greatest fear is that the Arctic has reached a "tipping point" beyond which nothing can reverse the continual loss of sea ice and with it the massive land glaciers of Greenland, which will raise sea levels dramatically.

Satellites monitoring the Arctic have found that the extent of the sea ice this August has reached its lowest monthly point on record, dipping an unprecedented 18.2 per cent below the long-term average.

Experts believe that such a loss of Arctic sea ice in summer has not occurred in hundreds and possibly thousands of years. It is the fourth year in a row that the sea ice in August has fallen below the monthly downward trend - a clear sign that melting has accelerated.

Scientists are now preparing to report a record loss of Arctic sea ice for September, when the surface area covered by the ice traditionally reaches its minimum extent at the end of the summer melting period.

Sea ice naturally melts in summer and reforms in winter but for the first time on record this annual rebound did not occur last winter when the ice of the Arctic failed to recover significantly.

Arctic specialists at the US National Snow and Ice Data Centre at Colorado University, who have documented the gradual loss of polar sea ice since 1978, believe that a more dramatic melt began about four years ago.

In September 2002 the sea ice coverage of the Arctic reached its lowest level in recorded history. Such lows have normally been followed the next year by a rebound to more normal levels, but this did not occur in the summers of either 2003 or 2004. This summer has been even worse. The surface area covered by sea ice was at a record monthly minimum for each of the summer months - June, July and now August.

Scientists analysing the latest satellite data for September - the traditional minimum extent for each summer - are preparing to announce a significant shift in the stability of the Arctic sea ice, the northern hemisphere's major "heat sink" that moderates climatic extremes.

"The changes we've seen in the Arctic over the past few decades are nothing short of remarkable," said Mark Serreze, one of the scientists at the Snow and Ice Data Centre who monitor Arctic sea ice.

Scientists at the data centre are bracing themselves for the 2005 annual minimum, which is expected to be reached in mid-September, when another record loss is forecast. A major announcement is scheduled for 20 September. "It looks like we're going to exceed it or be real close one way or the other. It is probably going to be at least as comparable to September 2002," Dr Serreze said.

"This will be four Septembers in a row that we've seen a downward trend. The feeling is we are reaching a tipping point or threshold beyond which sea ice will not recover."

The extent of the sea ice in September is the most valuable indicator of its health. This year's record melt means that more of the long-term ice formed over many winters - so called multi-year ice - has disappeared than at any time in recorded history.

Sea ice floats on the surface of the Arctic Ocean and its neighbouring seas and normally covers an area of some 7 million square kilometres (2.4 million square miles) during September - about the size of Australia. However, in September 2002, this dwindled to about 2 million square miles - 16 per cent below average.

Sea ice data for August closely mirrors that for September and last month's record low - 18.2 per cent below the monthly average - strongly suggests that this September will see the smallest coverage of Arctic sea ice ever recorded.

As more and more sea ice is lost during the summer, greater expanses of open ocean are exposed to the sun which increases the rate at which heat is absorbed in the Arctic region, Dr Serreze said.

Sea ice reflects up to 80 per cent of sunlight hitting it but this "albedo effect" is mostly lost when the sea is uncovered. "We've exposed all this dark ocean to the sun's heat so that the overall heat content increases," he explained.

Current computer models suggest that the Arctic will be entirely ice-free during summer by the year 2070 but some scientists now believe that even this dire prediction may be over-optimistic, said Professor Peter Wadhams, an Arctic ice specialist at Cambridge University.

"When the ice becomes so thin it breaks up mechanically rather than thermodynamically. So these predictions may well be on the over-optimistic side," he said.

As the sea ice melts, and more of the sun's energy is absorbed by the exposed ocean, a positive feedback is created leading to the loss of yet more ice, Professor Wadhams said.

"If anything we may be underestimating the dangers. The computer models may not take into account collaborative positive feedback," he said.

Sea ice keeps a cap on frigid water, keeping it cold and protecting it from heating up. Losing the sea ice of the Arctic is likely to have major repercussions for the climate, he said. "There could be dramatic changes to the climate of the northern region due to the creation of a vast expanse of open water where there was once effectively land," Professor Wadhams said. "You're essentially changing land into ocean and the creation of a huge area of open ocean where there was once land will have a very big impact on other climate parameters," he said.

Start your day with The Independent, sign up for daily news emails
Voices
There will be a chance to bid for a rare example of the SAS Diary, collated by a former member of the regiment in the aftermath of World War II but only published – in a limited run of just 5,000 – in 2011
charity appealTime is running out to secure your favourite lot as our auction closes at 2pm today
News
File: James Woods attends the 52nd New York Film Festival at Walter Reade Theater on September 27, 2014
peopleActor was tweeting in wake of NYPD police shooting
Sport
Martin Skrtel heads in the dramatic equaliser
SPORTLiverpool vs Arsenal match report: Bandaged Martin Skrtel heads home in the 97th-minute
News
Billie Whitelaw was best known for her close collaboration with playwright Samuel Beckett, here performing in a Beckett Trilogy at The Riverside Studios, Hammersmith
people'Omen' star was best known for stage work with Samuel Beckett
PROMOTED VIDEO
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Telesales & Customer Service Executives - Outbound & Inbound

£7 - £9 per hour: Recruitment Genius: Are you outgoing? Do you want to work in...

Recruitment Genius: National Account Manager / Key Account Sales

£30000 - £35000 per annum: Recruitment Genius: An opportunity has arisen for a...

Recruitment Genius: Operations Manager

£30000 - £35000 per annum: Recruitment Genius: An exciting opportunity to join...

Recruitment Genius: Recruitment Consultant

£30000 - £35000 per annum: Recruitment Genius: We have an excellent role for a...

Day In a Page

Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
The week Hollywood got scared and had to grow up a bit

The week Hollywood got scared and had to grow up a bit

Sony suffered a chorus of disapproval after it withdrew 'The Interview', but it's not too late for it to take a stand, says Joan Smith
From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?

Panto dames: before and after

From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?
Thirties murder mystery novel is surprise runaway Christmas hit

Thirties murder mystery novel is surprise runaway Christmas hit

Booksellers say readers are turning away from dark modern thrillers and back to the golden age of crime writing
Anne-Marie Huby: 'Charities deserve the best,' says founder of JustGiving

Anne-Marie Huby: 'Charities deserve the best'

Ten million of us have used the JustGiving website to donate to good causes. Its co-founder says that being dynamic is as important as being kind
The botanist who hunts for giant trees at Kew Gardens

The man who hunts giants

A Kew Gardens botanist has found 25 new large tree species - and he's sure there are more out there
The 12 ways of Christmas: Spare a thought for those who will be working to keep others safe during the festive season

The 12 ways of Christmas

We speak to a dozen people who will be working to keep others safe, happy and healthy over the holidays
Birdwatching men have a lot in common with their feathered friends, new study shows

The male exhibits strange behaviour

A new study shows that birdwatching men have a lot in common with their feathered friends...
Diaries of Evelyn Waugh, Virginia Woolf and Noël Coward reveal how they coped with the December blues

Famous diaries: Christmas week in history

Noël Coward parties into the night, Alan Clark bemoans the cost of servants, Evelyn Waugh ponders his drinking…
From noble to narky, the fall of the open letter

From noble to narky, the fall of the open letter

The great tradition of St Paul and Zola reached its nadir with a hungry worker's rant to Russell Brand, says DJ Taylor
A Christmas ghost story by Alison Moore: A prodigal daughter has a breakthrough

A Christmas ghost story by Alison Moore

The story was published earlier this month in 'Poor Souls' Light: Seven Curious Tales'