UK water use 'worsening global crisis'

By Richard Black Environment correspondent, BBC News

Climatic change will increase water stress in many places, the report says

The amount of water used to produce food and goods imported by developed countries is worsening water shortages in the developing world, a report says.

The report, focusing on the UK, says two-thirds of the water used to make UK imports is used outside its borders.

The Engineering the Future alliance of professional engineering bodies says this is unsustainable, given population growth and climate change.

It says countries such as the UK must help poorer nations curb water use.

"We must take account of how our water footprint is impacting on the rest of the world," said Professor Roger Falconer, director of the Hydro-Environmental Research Centre at Cardiff University and a member of the report's steering committee.

If the water crisis becomes critical, it will pose a serious threat to the UK's future development Professor Peter Guthrie

"If we are to prevent the 'perfect storm', urgent action is necessary."

The term perfect storm was used last year by the UK government's chief scientist, Professor John Beddington, to describe future shortages of energy, food and water.

Forecasts suggest that when the world's population soars beyond 8bn in 20 years time, the global demand for food and energy will jump by 50%, with the need for fresh water rising by 30%.

But developing countries are already using significant proportions of their water to grow food and produce goods for consumption in the West, the report says.

"The burgeoning demand from developed countries is putting severe pressure on areas that are already short of water," said Professor Peter Guthrie, head of the Centre for Sustainable Development at Cambridge University, who chaired the steering group.

WATER TRENDS How availability, use and needs are changing across the world In graphics

"If the water crisis becomes critical, it will pose a serious threat to the UK's future development because of the impact it would have on our access to vital resources."

Key to the report is the concept of "embedded water" - the water used to grow food and make things.

Embedded in a pint of beer, for example, is about 130 pints (74 litres) of water - the total amount needed to grow the ingredients and run all the processes that make the pint of beer.

A cup of coffee embeds about 140 litres (246 pints) of water, a cotton T-shirt about 2,000 litres, and a kilogram of steak 15,000 litres.

Using this methodology, UK consumers see only about 3% of the water usage they are responsible for.

The average UK consumer uses about 150 litres per day, the size of a large bath.

Ten times as much is embedded in the British-made goods bought by the average UK consumer; but that represents only about one-third of the total water embedded in all the average consumer's food and goods, with the remainder coming from imports.

The UK is not unique in this - the same pattern is seen in most developed countries.

FUTURE WATER STRESS Interactive map: Rising water stress in a changing world

The engineering institutions say it means nations such as the UK have a duty to help curb water use in the developing world, where about one billion people already do not have sufficient access to clean drinking water.

UK-funded aid projects should have water conservation as a central tenet, the report recommends, while companies should examine their supply chains and reduce the water used in them.

This could lead to difficult questions being asked, such as whether it is right for the UK to import beans and flowers from water-stressed countries such as Kenya.

While growing crops such as these uses water, selling them brings foreign exchange into poor nations.

In the West, the report suggests, concerns over water could eventually lead to goods carrying a label denoting their embedded water content, in the same way as electrical goods now sport information about their energy consumption.

The Engineering the Future alliance includes the Institution of Civil Engineers (ICE), the Royal Academy of Engineering (RAE) and the Chartered Institute of Water and Environmental Management (CIWEM).

The Icelandic eruption

Icelandic volcanic ash alert grounds UK flights

The Icelandic eruption - airport officials say the ash represents a very serious risk to aircraft

Airline passengers are facing massive disruption across the UK after an ash cloud from a volcanic eruption in Iceland grounded planes.

In Scotland, all airports are shut and there is disruption at many others including Manchester, Liverpool, Stansted, Newcastle and Birmingham.

The Air Traffic Control Service (Nats) imposed restrictions after the Met Office warned ash could damage engines.

Passengers are being advised to contact their airlines prior to travel.

Experts have warned that the tiny particles of rock, glass and sand contained in the ash cloud would be sufficient to jam aircraft engines.

'Significant disruption'

Aberdeen, Edinburgh and Glasgow airports were shut as Nats said it was restricting flights "in accordance with international civil aviation policy".

The ash cloud disrupted all flights to and from Manchester with a similar picture at Newcastle airport where all arrivals were cancelled and all outbound flights either cancelled or subject to indefinite delay.

Liverpool's John Lennon airport suspended all flights until at least 1300BST.

Airports in Scotland were the first to suspend flights overnight

British Airways said it had cancelled all domestic flights for the whole of Thursday, which affected flights at London's Gatwick, Heathrow and City airports.

Birmingham airport warned of severe disruption with about 90% of flights cancelled, and there were problems reported at East Midlands, Leeds Bradford, Cardiff and Bristol.

Most flights were suspended at Belfast International Airport and George Best Belfast City Airport, with some in and out of Dublin airport also hit.

A Nats spokesman said: "The Volcanic Ash Advisory Centre has issued a forecast that the ash cloud from the volcanic eruption in Iceland will track over Europe tonight.

"Nats is working with Eurocontrol and our colleagues in Europe's other air navigation service providers to take the appropriate action to ensure safety in accordance with international aviation policy."

Engines shut

The European air safety body, Eurocontrol, said the cloud of ash had reached 55,000ft and was expected to move through northern UK and Scotland by 1300BST.

Brian Flynn, assistant head of operations of its central flow management unit, told the BBC: "As it moves toward the Netherlands and Belgium it will dissipate and lose intensity, like any weather phenomenon. But we don't know what the extent of it will be."

VOLCANIC ASH CLOUD The eruption in the Eyjafjallajoekull area is the second to occur in a month This eruption has released ash to significantly greater heights Volcanic ash contains tiny particles of rock and even glass, which can wreak havoc with machinery A 1982 BA flight unknowingly flew into an ash cloud, shutting down all four engines Animated guide: Volcanoes

Further south, five easyJet flights due to depart from Stansted airport in Essex were cancelled, along with all northbound flights from Southampton and Newquay airports.

Bournemouth airport grounded a flight to Dublin but said all other departures were on schedule.

Met Office forecaster Philip Avery said the ash could take several days to clear.

He said: "It is showing up on imagery at the moment, extending down as far as the Faroes but it looks as though the wind will drag it a good deal further south.

"Nats has good cause to be very cautious about this because in about 1982 a British Airways jumbo had the unnerving experience of having all four engines shut down as it flew through a plume of volcanic ash."

There was a nearly identical incident on 15 December 1989 when KLM Flight 867, a B747-400 from Amsterdam to Anchorage, Alaska, flew into the plume of the erupting Mount Redoubt, causing all four engines to fail.

Once the flight cleared the ash cloud, the crew was able to restart each engine and then make a safe landing at Anchorage, but the aircraft was substantially damaged.

The volcanic ash cloud reached about 55,000ft, Eurocontrol says

A BAA spokesman said: "Passengers intending to fly today are asked to contact their airline for further information and should expect disruption in the coming hours.

The Royal Air Force has confirmed it will maintain its search and rescue operations.

A spokesman said: "We will continue to provide full search and rescue cover, however we will consider all requests we get on a case by case basis.

"The ash is mainly affecting the air traffic control radar but we can fly in cloud and reduced visibility.

The eruption under a glacier in the Eyjafjallajoekull area of Iceland is the second in the country in less than a month.

A Nats spokesperson said the volcano was still erupting.

Japan annual whale hunt 'halved by activists'

By Roland Buerk BBC News, Tokyo

Anti-whaling activists aim to prevent the hunt from going ahead

Japan's whaling fleet has revealed how much anti-whaling activists disrupted the annual hunt off Antarctica.

The ships have returned to port with just over half as many whales - 507 - as they had set out to catch.

Whalers said they were angry, and blamed what they described as "violent interference" from the anti-whaling Sea Shepherd Conservation Society.

Clashes at sea between Sea Shepherd and the whaling ships paralysed the hunt for 31 days.

The last ship of the whaling fleet to return home sailed into Tokyo bay, with much of the hunt's catch in her hold.

The whalers had set out late last year to kill nearly 1,000 whales in the waters off Antarctica, but they caught 506 minke whales and one fin whale.

It is the smallest catch for years.

One of the Sea Shepherd activists, Peter Bethune, is awaiting trial in Japan after boarding a harpoon ship and trying to perform a citizen's arrest on her captain.

Prosecutors have charged him with five crimes. If convicted he could go to prison.

Commercial whaling has been banned worldwide since 1986 but Japan justifies its annual hunt as scientific research.

Meat not used for study ends up in restaurants and shops

NHS left with 34m stockpile of swine flu jabs

By Nick Triggle Health reporter, BBC News

Priority groups and health workers have been offered the vaccine

The NHS has more than 34 million unused doses of swine flu vaccine despite agreeing deals to break its contracts.

The UK government had signed deals with two firms - Baxter and GlaxoSmithKline - for more than 120m doses of the jabs.

But just 44m will now be bought as cases have petered out since December. Of these, 6m have already been used and 3.8m is being sent to help Africa.

Ministers said the renegotiated deal was good value, but the Tories said millions of pounds had been wasted.

This is a careless waste of precious NHS money Andrew Lansley, shadow health secretary

Of the nearly 44m vaccines that the UK has agreed to pay for, 6m have already been used on priority groups and health workers, while 3.8m are being handed to the World Health Organization for Africa.

Of the rest, 10.6m is already with GPs who will be ready to act if more people entitled to the jab come forward. But the remaining 23.6m will be held in reserve.

Estimates have put the value of the stockpile at between £100m to £150m, although the government has refused to confirm cost saying it was commercially confidential.

Health Secretary Andy Burnham said: "I am pleased we have reached an agreement that is good value for the taxpayer and means that the department has retained a strategic stockpile to protect the UK population without incurring a cancellation fee."

It is also possible the vaccine could be used to combat seasonal flu this winter as it is thought the swine flu virus will become the dominant strain.

Under the terms of the deal with GSK, the government is also purchasing anti-flu drugs as well as bird flu vaccine. These will be held in reserve in case a completely different pandemic emerges.

Shadow health secretary Andrew Lansley said: "This is a careless waste of precious NHS money. Labour failed to ensure there were proper break clauses in the contracts which means that British taxpayers have got an extremely bad deal."

Liberal Democrat health spokesman Norman Lamb added: "Today's announcement underscores the need for a thorough independent examination of how the NHS responded to the swine flu pandemic."

Does red meat give you bowel cancer?

By Clare Murphy Health reporter, BBC News

Everyone agrees you can still enjoy a steak

A bitter row has broken out between members of the British meat industry and the World Cancer Research Fund over whether red meat increases the risk of bowel cancer. What do we know about this link?

The WCRF says the evidence that red and processed meats increase the risk of colorectal cancer is "convincing", and since 2007 - when it published a major report on lifestyle and cancer - has urged the public to limit their consumption of steak and sausages.

These conclusions, claim an array of organisations representing meat producers, are flawed. They point to a number of independent scientists who have questioned the conviction with which the link between red meat and cancer was presented in the report.

The WCRF has published a list of "minor errors" with the report - some relating to the findings on red meat and bowel cancer - but says it has no intention of altering the conclusions based on an expert panel's review of the scientific literature.

According to the recommendations, red meat should be consumed in modest amounts, and salami and ham should almost always be avoided.

Veggies' risk

This latest spat is driven by the fact that the government's Scientific Advisory Committee on Nutrition cited the WCRF report in draft conclusions on the impact of cutting red meat on the nation's iron levels.

The WCRF findings, argues the lobby group for the English beef and lamb industry - EBLEX, should not be used as a "point of reference".

It's an enigma - nobody knows the truth Professor Tim Key Oxford University

But there have already been clashes within the pages of the leading scientific journal on diet and disease.

In a letter last year to the American Journal of Clinical Nutrition, Professor Stewart Truswell of the University of Sydney questioned why several large studies which found no link had been discarded by the panel, and also pinpointed errors in the reporting of data.

In response, the WCRF explained that a series of studies on meat had been omitted because they did not report on red meat specifically, but it did accept some mistakes in the reporting of the data. This did not however "change the overall picture", it stressed.

Many in the scientific community were however taken aback by the findings of a large study into the relationship between diet and cancer, published in the same nutrition journal last year.

Looking at all the research, the evidence linking red and processed meat and bowel cancer is overwhelming Professor Martin Wiseman WCRF

The European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford), which followed 65,000 people during the 1990s, found that far from being protected from bowel cancer as anticipated, vegetarians in fact displayed a slightly higher incidence of this form of the disease.

It ran counter to the the findings of a previous arm of the EPIC study which suggested that very high levels of red and processed meat consumption - more than two pork chops every day - was associated with a 35% higher risk of bowel cancer when compared with those who rarely ate red meat.

"Our findings did come as something of a surprise. At the simplest level if meat causes colorectal cancer you would expect to see lower rates in the vegetarians, and we didn't," says Professor Tim Key, the epidemiologist who led the Oxford study.

"It's definitely a really tricky area. It's an enigma - nobody knows the truth. We can be much clearer on the relationship between obesity and cancer, or alcohol and cancer, because it's relatively easy to measure these things. Understanding the exact role specific foods play is much harder to quantify.

"There is a lot of evidence for meat, but it's not completely compelling."

It's not no

The WCRF says the Oxford findings on vegetarians could be explained by chance, noting there were only 28,000 non-meat eaters in the study. Vegetarians, it said, may consume fewer dairy products - "and our report found that milk probably reduces risk of bowel cancer".

RED MEAT CONTENT Medium steak: 145g Pork chop: 75g Spaghetti bolognese with beef: 140g Serving of roast beef: 90g

"We are in the process of reviewing the evidence on meat and bowel cancer and that is expected to be published later this year," says Professor Martin Wiseman, the project director. "But no research has been published since our report to make us question the finding that there is convincing evidence red and processed meat increase risk of bowel cancer."

"It is easy for anyone to find an individual study to support almost any view they wish to hold. But looking at all the research, the evidence linking red and processed meat and bowel cancer is overwhelming."

The WRCF does not in any event advocate a vegetarian diet, or a complete abstention from red meat. In fact its recommendations that people keep within 500g a week - the equivalent of a fair serving of roast beef on five of those days - is not far off average consumption.

Nell Barrie, Cancer Research UK's science information officer, said: "Two of the world's largest studies on diet and cancer have found that people are more likely to develop some cancers, such as bowel cancer, if they eat too much red or processed meat.

"Cutting down on these foods can help to reduce the risk of developing cancer."

But cancer specialist Professor Karol Sikora said those who enjoyed eating red meat should continue to do so.

"We have created a nightmare situation of confusing messages based on very little evidence. Eating red meat in the context of a balanced diet should really not be viewed as a problem.

"Yes, avoid a high calorie, high fat diet - but by all means enjoy that steak."

a study into the link between diet and disease has found.

Five-a-day has little impact on cancer, study finds

By Clare Murphy Health reporter, BBC News

Researchers are trying to harness key chemicals like lycopene in tomatoes

Eating more fruit and vegetables has only a modest effect on protecting against cancer, a study into the link between diet and disease has found.

The study of 500,000 Europeans joins a growing body of evidence undermining the high hopes that pushing "five-a-day" might slash Western cancer rates.

The international team of researchers estimates only around 2.5% of cancers could be averted by increasing intake.

But experts stress eating fruit and vegetables is still key to good health.

In 1990, the World Health Organization recommended that everyone consume at least five portions of fruit and vegetables a day to prevent cancer and other chronic diseases.

The advice has formed a central plank of public health campaigns in many developed countries. It has been promoted in the UK since 2003 and in the US for nearly two decades.

But research has failed to substantiate the suggestion that as many as 50% of cancers could be prevented by boosting the public's consumption of fruit and vegetables.

It's still a good idea to eat your five-a-day but remember that fruits and vegetables are pieces in a much larger lifestyle jigsaw Yinka Ebo Cancer Research UK

This latest study, which analysed recruits from 10 countries to the highly-regarded European Prospective Investigation into Cancer and Nutrition, confirms that the association between fruit and vegetable intake and reduced cancer risk is indeed weak.

The team, led by researchers from the Mount Sinai School of Medicine, in New York, took into account lifestyle factors such as smoking and exercise when drawing their conclusions.

But writing in the Journal of the National Cancer Institute, they said they could not rule out that even the small reduction in cancer risk seen was down to the fact that the kind of people who ate more fruit and vegetables lived healthier lives in many other respects too.

Broccoli not biscuits

In the best case scenario, an extra two portions of fruit and vegetables each day could prevent 2.6% of cancers in men and 2.3% of cases in women, the study concluded.

Research should focus more sharply on specific fruits and vegetables and their constitutents Walter Willett Harvard School of Public Health

Vegetables, which tend to be richer in nutrients, appeared to be more beneficial than fruits, while heavy drinkers seemed to gain the most from a higher intake of both when it came to protection from cancers caused by alcohol and smoking.

In an accompanying editorial, Professor Walter Willet of Harvard University said the research strongly confirmed the findings of other studies, showing "that any association of intake and fruits and vegetables with risk of cancer is weak at best".

But he stressed specific substances contained in certain fruit and vegetables, if harnessed, could still have an important, protective effect.

Substantial evidence suggests lycopene from tomatoes, for instance, may reduce the risk of prostate cancer, while chemicals in broccoli are thought to stimulate a gene which protects against bowel cancer.

And data still suggests fruit and vegetables may provide protection against cardiovascular disease, one of the major killers in the developed world - although this too has yet to be proven categorically.

Prof Sikora: 'Eating five-a-day still has health benefits'

Keeping lean

But while the links between diet and cancer remain unclear, obesity is now seen as an established risk factor.

Fruit and vegetables could therefore be beneficial just by virtue of taking the place of more calorific fare, health experts say.

In any event, a reduced risk of 2.5% should not be dismissed out of hand, the World Cancer Research Fund argues.

"For the UK, this works out as about 7,000 cases a year, which is a significant number," says Dr Rachel Thompson from the charity, which in a major 1997 report said there was "convincing evidence" of the protective effect of fruit and vegetables.

Yinka Ebo of Cancer Research UK said: "It's still a good idea to eat your five-a-day but remember that fruits and vegetables are pieces in a much larger lifestyle jigsaw.

"There are many things we can do to lower our chances of developing cancer such as not smoking, keeping a healthy weight, cutting down on alcohol, eating a healthy balanced diet, being physically active and staying safe in the sun."

Staffordshire hospital battles resistant superbug

By Michele Paduano BBC West Midlands health correspondent

The infections were almost all on a kidney ward at the hospital

A strain of superbug unique to Staffordshire has killed a kidney patient and infected at least seven others, the BBC has learned.

Klebsiella pneumoniae affected 13 patients on Ward 29 at University Hospital of North Staffordshire.

The dead patient and seven others, developed a resistant strain of the disease.

A hospital spokesman said: "Eight [patients] have a new strain that has not been seen elsewhere."

It is understood the infection was contained by late February with 13 cases still being treated.

'Highly contagious'

Hospital microbiologist George Orendi said was surprised by the contagious nature of Klebsiella.

He said: "What makes it of concern is the number of patients that we have found with the resistant strain.

"It is transmitted between patients. This particular type has not been seen elsewhere."

The hospital has cleaned ward 29 to intensive care standards and all patients on the ward, which is used for kidney patients, are now being screened weekly for Klebsiella.

Health professionals say the strain of superbug to which Klebsiella belongs is capable of adapting far more quickly than MRSA.

A University Hospital of North Staffordshire spokesperson said: "Various different strains have been identified in the 13 cases currently at University Hospital.

"Eight have a new strain that has not been seen elsewhere.

"One of the patients who developed the infection had a number of other serious conditions and has subsequently died."

hunting for body parts and tissues to satisfy demand for amulets

Folk medicine poses global threat to primate species

Traditional folk medicine poses a significant and ongoing threat to the future of primates around the world.

According to a major scientific survey at least 101 primate species are still used in traditional folk practices and in magic or religious rituals.
For example, spider monkeys are eaten to treat rheumatism, while gorilla parts are given to pregnant women.
Such practises are accelerating the declines of many already vulnerable species, say the survey's authors.
Details of the survey are published in Mammal Review, the journal of the UK Mammal Society.
Of 390 species studied, 101, or more than a quarter, are regularly killed for their body parts, with 47 species being used for their supposed medicinal properties, 34 for use in magical or religious practices, and 20 for both purposes.

MONKEY MEDICINE Around the world, the number of primate species used in traditional medicine varies: Neotropics: 19 of 139 species Africa: 25 of 79 species Madagascar: 10 of 93 species Asia: 47 of 79 species

These primates belong to 38 genera and 10 different families, ranging from monkeys such as langurs and macaques to apes such as gorillas, and smaller primates such as lorises.
"Despite laws, use and trade of the species for medicinal purposes persists," says Professor Romulo Alves of the State University of Paraiba in Brazil, who conducted the survey with colleagues.
The trade in all primate species is tightly regulated by CITES legislation.
Yet despite this, their body parts are being put to a range of uses.
Curing ailments
At least 30% of the primates used are administered to treat one than one ailment.
Black-faced spider monkeys (Ateles chamek) and brown or tufted capuchins (Cebus apella) are each used to treat more than six ailments, for example, with spider monkey body parts used in Bolivia to cure snake bites, spider bites, fever, coughs, colds, shoulder pain, sleeping problems and leishmaniasis.

Assamese macaques are eaten to treat rheumatism

In India, say the survey's authors, many people believe that eating the blood of macaques (Macaca assamensis and M. mulatta) treats asthma.
Other monkeys or lorises have their bones or skulls ground up into powder administered with tea, or have their gall bladders ingested or blood or fat used as ointments.
Matter of faith
Primates are also commonly associated with myths within the faiths of different countries, say the survey's authors.
For example, in Sierra Leone, a small piece of chimpanzee bone is sometimes tied around the waists or wrists of children in the belief that it makes them stronger as they grow into adulthood.

ON THE BRINK Gorillas might be extinct within 20 years, conservationists warn Two of the world's rarest primates are to be helped by the creation of new nature reserves in south-east Asia Watch some of the BBC's best films of wild primates

In India, the eye of the Hanuman langur (Semnopithecus entellus) is sometimes worn in an amulet to increase courage.
Although many primates are killed for magical or religious purposes, the authors point out that folk beliefs can in some cases help conserve species.
In parts of Asia, Hindu beliefs help protect species such as long-tailed macaques (Macaca fascicularis) in Bali or grey langurs (Semnopithecus spp) in India.
While in the village of Bossou in the Republic of Guinea, the Manon people consider chimpanzees sacred.
The researchers who conducted the survey also emphasise that many pressures, such as habitat loss, subsistence hunting and the trade in bushmeat, are decreasing primate numbers.

Chimp parts are thought make infants stronger

But the trade in primate body parts is often overlooked, yet could help drive many species toward extinction.
Of the 101 primates recorded by the survey, 12 are classified by the International Union for the Conservation of Nature as being critically endangered, 23 as endangered and 22 as vulnerable.
For example, in Vietnam, pygmy lorises are severely threatened, but the biggest hazard to them is now the high prices people will pay to smuggle the animals into China to be used in medicines.
Many langur species are similarly threatened, not just from subsistence hunting and habitat loss but by hunting for body parts and tissues to satisfy demand for amulets, remedies and aphrodisiacs

Gulf Stream 'is not slowing down'

By Richard Black Environment correspondent, BBC News

Data came from the global network of Argo floats in the oceans

The Gulf Stream does not appear to be slowing down, say US scientists who have used satellites to monitor tell-tale changes in the height of the sea.

Confirming work by other scientists using different methodologies, they found dramatic short-term variability but no longer-term trend.

A slow-down - dramatised in the movie The Day After Tomorrow - is projected by some models of climate change.

The research is published in the journal Geophysical Research Letters.

The stream is a key process in the climate of western Europe, bringing heat northwards from the tropics and keeping countries such as the UK 4-6C warmer than they would otherwise be.

It forms part of a larger movement of water, the Atlantic Meridional Overturning Circulation, which is itself one component of the global thermohaline system of currents.

Between 2002 and 2009, the team says, there was no trend discernible - just a lot of variability on short timescales.

The Atlantic overturning circulation is still an important player in today's climate Josh Willis, Nasa

The satellite record going back to 1993 did suggest a small increase in flow, although the researchers cannot be sure it is significant.

"The changes we're seeing in overturning strength are probably part of a natural cycle," said Josh Willis from Nasa's Jet Propulsion Laboratory (JPL) in California.

"The slight increase in overturning since 1993 coincides with a decades-long natural pattern of Atlantic heating and cooling."

Short measures

The first observations suggesting the circulation was slowing down emerged in 2005, in research from the UK's National Oceanography Centre (NOC).

Using an array of detectors across the Atlantic and comparing its readings against historical records, scientists suggested the volume of cold water returning southwards could have fallen by as much as 30% in half a century - a significant decline.

The warm surface water sinks in the Arctic and flows back southwards at the bottom of the ocean, driving the circulation.

However, later observations by the same team showed that the strength of the flow varied hugely on short timescales - from one season to the next, or even shorter.

But they have not found any clear trend since 2004.

The global thermohaline circulation takes warm and cold water across the oceans

Rapid relief

The NOC team now has a chain of instruments in place across the Atlantic, making measurements continuously.

"In four-and-a-half years of measurement, we have found there is a lot of variability, and we're working to explain it," said NOC's Harry Bryden.

The quantities of water involved are huge, varying between four million and 35 million tonnes of water per second.

The array is part of the UK-funded Rapid project, which aims to refine understanding of potentially large climate change impacts that could happen in short periods.

Professor Bryden's team calculates that their system is good enough to detect a long-term change in flow of about 20% - but it has not happened yet.

He believes the JPL approach - using satellite altimeters, instruments that can measure sea height precisely, and the Argo array of autonomous floating probes - could potentially add useful data to that coming from long-term on-site monitoring arrays.

But, he points out: "The method concentrates only on the upper [northward] flow - it doesn't give you much information on the returning flow southward."

Fantasy and reality

Driven by Hollywood, a popular image of a Gulf Stream slowdown shows a sudden catastrophic event driving snowstorms across the temperate lands of western Europe and eastern North America.

That has always been fantasy - as, said Josh Willis, is the idea that a slow-down would trigger another ice age.

"But the Atlantic overturning circulation is still an important player in today's climate," he added.

"Some have suggested cyclic changes in the overturning may be warming and cooling the whole North Atlantic over the course of several decades and affecting rainfall patterns across the US and Africa, and even the number of hurricanes in the Atlantic."

'X-woman'

DNA identifies new ancient human dubbed 'X-woman'

By Paul Rincon Science reporter, BBC News

The finger bone was unearthed in 2008 at Denisova Cave

Scientists have identified a previously unknown type of ancient human through analysis of DNA from a finger bone unearthed in a Siberian cave.

The extinct "hominin" (human-like creature) lived in Central Asia between 48,000 and 30,000 years ago.

An international team has sequenced genetic material from the fossil showing that it is distinct from that of Neanderthals and modern humans.

Details of the find, dubbed "X-woman", have been published in Nature journal.

Ornaments were found in the same ground layer as the finger bone, including a bracelet.

Professor Chris Stringer, human origins researcher at London's Natural History Museum, called the discovery "a very exciting development".

Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far Svante Paabo Max Planck Institute for Evolutionary Anthropology

"This new DNA work provides an entirely new way of looking at the still poorly-understood evolution of humans in central and eastern Asia."

The discovery raises the intriguing possibility that three forms of human - Homo sapiens, Neanderthals and the species represented by X-woman - could have met each other and interacted in southern Siberia.

The tiny fragment of bone from a fifth finger was uncovered by archaeologists working at Denisova Cave in Siberia's Altai Mountains in 2008.

An international team of researchers extracted mitochondrial DNA from the bone and compared the genetic code with those from modern humans and Neanderthals.

Origin unknown

Mitochondrial DNA comes from the cell's powerhouses and is passed down the maternal line only.

The analysis carried out by Johannes Krause from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues revealed the human from Denisova last shared a common ancestor with modern humans and Neanderthals about one million years ago.

This is known as the divergence date; essentially, when this human's ancestors split away from the line that eventually led to Neanderthals and ourselves.

The Neanderthal and modern human evolutionary lines diverged much later, around 500,000 years ago. This shows that the individual from Denisova is the representative of a previously unknown human lineage that derives from a hitherto unrecognised migration out of Africa.

"Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," said co-author Professor Svante Paabo, also from the Max Planck Institute for Evolutionary Anthropology.

The divergence date of one million years is too young for the Denisova hominin to have been a descendent of Homo erectus, which moved out of Africa into Asia some two million years ago.

And it is too old to be a descendent of Homo heidelbergensis, another ancient human thought to have originated around 650,000 years ago. However, for now, the researchers have steered away from describing the specimen as a new species.

Dr Krause said the ground layer in which the Denisova hominin fragment was found contain tools which are similar to those made by modern humans in Europe.

Slice of time

"We have ornaments, there is a bracelet, so there are several elements in the layers that are usually associated with modern human archaeology," he told BBC News.

"That's quite interesting, but of course, it is hard to prove that the bone is strongly associated to this archaeology, because it is possible that bones could have moved within the site.

"We are also not sure how exactly the excavation was done. It could have come from a deeper layer, so that's hard to say."

The "Hobbit" persisted until 12,000 years ago on Flores

Professor Clive Finlayson, director of the Gibraltar Museum, said the find presented a number of questions, such as to what extent culture could continue to be used as a proxy for different prehistoric human groups.

Referring to his research on Neanderthals and modern humans in southern Iberia, he told BBC News: "The assumption is that when one group - the moderns - arrives the other group disappears. Here you have a very clear example of co-existence for long periods.

"Where is the rule that says you can have only one species in an area? Especially if they're at low density... the implications are big."

The research contributes to a more complex picture that has been emerging of humankind during the Late Pleistocene, the period when modern humans left Africa and started to colonise the rest of the world.

Professor Finlayson has previously argued: "A time slice at a point in the late Pleistocene would reveal a range of human populations spread across parts of Africa, Eurasia and Oceania.

"Some would have been genetically linked to each other, behaving as sub-species, while the more extreme populations may well have behaved as good species with minimal or no interbreeding."

It was long known that modern humans overlapped with Neanderthals in Europe, apparently for more than 10,000 years.

But in 2004, researchers discovered that a dwarf species of human, dubbed "The Hobbit", was living on the Indonesian island of Flores until 12,000 years ago - long after modern humans had colonised the region.

Difficult classification

Neanderthals appear to have been living at Okladnikov Cave in the Altai Mountains some 40,000 years ago. And a team led by Professor Anatoli Derevianko, from the Russian Academy of Sciences, has also found evidence of a modern human presence in the region at around the same time.

Professor Stringer commented: "Another intriguing question is whether there might have been overlap and interaction between not only Neanderthals and early moderns in Asia, but also, now, between either of those lineages and this newly-recognised one.

"The distinctiveness of the mitochondrial DNA patterns so far suggests that there was little or no interbreeding, but more extensive data will be needed from other parts of the genome, or from the fossils, for definitive conclusions to be reached."

The archaeology of Denisova presents a puzzle of sorts

Experts have been wondering whether X-woman might have links with known fossil humans from Asia, which have controversial classifications.

"Certain enigmatic Asian fossils dated between 250,000-650,000 years ago such as Narmada (in India), and Yunxian, Dali and Jinniushan (in China) have been considered as possible Asian derivatives of Homo heidelbergensis, so they are also potential candidates for this mystery non-erectus lineage," said Prof Stringer.

"However, there are other and younger fragmentary fossils such as the Denisova ones themselves, and partial skulls from Salkhit in Mongolia and Maba in China, which have been difficult to classify, and perhaps they do signal a greater complexity than we have appreciated up to now."

Other experts agreed that while the Siberian specimen may be a new species, this has yet to be shown.

"We really don't know," Ian Tattersall of the American Museum of Natural History in New York, told the Associated Press news agency.

Dr Tattersall, who wasn't involved in the new research, added: "The human family tree has got a lot of branchings. It's entirely plausible there are a lot of branches out there we don't know about."