Best of our wild blogs: 5 Jul 11

9-10 Jul (Sat & Sun): Biodiversity talks at the Botanic Gardens
from Celebrating Singapore's BioDiversity!

Underwater garden of Sentosa at Serapong
from wonderful creation and wild shores of singapore and Psychedelic Nature

Revisiting the Mantidfly!
from Macro Photography in Singapore

Little Grebe feeding on fish
from Bird Ecology Study Group

Monkey see, monkey do: Monkeys open lids of recycling bins at MacRitchie Park
from The Lazy Lizard's Tales

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Additional $140 million for water research

Jessica Cheam Straits Times 5 Jul 11;

SINGAPORE has pumped fresh money into local water research to keep its edge as the leader in water technologies.

The sector will receive $140 million to promote research and development (R&D) efforts, with the aim of converting these ideas into practical water solutions, Deputy Prime Minister Tharman Shanmugaratnam said yesterday.

That would in turn attract more investment and create more jobs in the industry.

The fresh funds allocated by the National Research Foundation (NRF) will bring the total R&D budget for the sector to $470 million.

Mr Tharman made the announcement at the opening ceremony of the Singapore International Water Week (SIWW). Into its fourth year, the high-profile event features new water technologies and brings together global experts and leaders who will discuss how to cope with issues such as rising water demand.

Speaking to an audience of 1,800 last night, Mr Tharman said it is important to continue investing in R&D, even if 'the gestation periods can be long before the pay-offs to new technologies are realised'.

'The journey towards water security will always be a work-in-progress for Singapore, as new challenges emerge in the urban environment,' said Mr Tharman, who is Finance and Manpower Minister.

But such challenges are not unique to Singapore, he pointed out. 'Cities around the world will have to contend with issues such as weather extremities in the context of urbanisation, increasing water demand and higher public expectations.'

Singapore, for instance, has had to grapple with the problem of flooding. Just last month, heavy rainfall submerged parts of eastern and central Singapore, including the Tanglin-Cuscaden area. A panel of experts has since been set up to review the island's drainage system and flood-prevention measures.

In 2006, the NRF was set up with a five-year $5 billion budget, and had set aside $330 million for water research.

Last year, it received a $16.1 billion injection for 2011 to 2015 to support research, innovation and enterprise. The $140 million will come out of this fund.

Mr Tharman noted that under the NRF's initiatives, some water projects funded include research into membranes used to sieve out impurities in water, and seawater desalination that uses less energy.

With these fresh investments, Mr Tharman said Singapore is hopeful that it will hit its goal of growing the economic contribution from the water sector from $500 million in 2003 to $1.7 billion by 2015. It also hopes for a doubling of jobs to 11,000 in the industry by then.

Besides investing in R&D, countries can also see challenges as opportunities, said Mr Tharman.

He cited the Netherlands's Delta Programme, which acquires land for the temporary storage of excess river water. When dry, these areas double up as parkland for recreational activities.

There is a similar initiative in Singapore, he said. The Active, Beautiful, Clean or ABC Waters programme, driven by national water agency PUB, transforms 'utilitarian drains and canals into beautiful and vibrant rivers and streams'.

He also called for a closer collaboration between the public sector, academia and private sector firms.

One example is the Singapore-Delft Water Alliance set up in 2007 by the National University of Singapore, consultancy firm Deltares and PUB. The tie-up aims to develop solutions for the urban water cycle, and it will launch a new Aquatic Science Centre - the first in Asia - tomorrow.

'By working across boundaries... we can potentially fast-track the development of solutions at a lower total cost, and make the challenge less daunting for everyone,' he said.

Earlier in the day, Environment Minister Vivian Balakrishnan attended the South-east Asia Water Ministers Forum, part of the SIWW.

He noted that issues of water management have become increasingly important because South-east Asian countries are particularly vulnerable to extreme weather events, due to their extensive, heavily populated coasts.

'(The) forum is a stepping stone towards greater commitment in resolving some of these issues,' he said.

Prime Minister Lee Hsien Loong will address SIWW delegates today

Water R&D to get boost
Ryan Huang Channel NewsAsia 4 Jul 11;

SINGAPORE: Research and development in Singapore's water sector is set to receive a boost.

This comes in a fresh funding of S$140 million from the National Research Foundation.

This is on top of the S$330 million previously committed in 2006.

The news was announced by Deputy Prime Minister Tharman Shanmugaratnam, who stressed the importance of investing in new technologies for the long term.

Mr Tharman was speaking at the opening ceremony of the Singapore International Water Week (SIWW) 2011.

Finding new ways to develop sustainable water solutions will be key to Singapore's water security, and the government believes continued investment in the sector will be crucial towards this goal.

It is raising the amount committed to promote R&D in the sector by nearly 50 per cent to a total of S$470 million.

DPM Tharman, who is also Minister for Finance and Manpower, said: "So far, the projects funded under this initiative include those looking into domains like advanced membrane processes, bio-mimicry and low-energy seawater desalination.

"We are hopeful that with these investments, we will achieve our goal of growing the value-added contribution from this sector from S$0.5 billion in 2003 to S$1.7 billion by 2015, and doubling jobs in the sector to 11,000 by then".

Another key factor to grow the industry involves the private sector.

One latest example is the award of a contract by national water agency PUB to ST Electronics.

This is to create a system to help it manage its resources better.

Called an Intelligent Water Management System, it aims to enhance PUB's capability to integrate real-time information on water resources in Singapore and manage water operations across the entire water supply, water catchment, used water and drainage systems more efficiently.

The project is expected to be completed in the second half of 2012.

Another example is through Public Private Partnerships (PPP) such as the Ulu Pandan NEWater Plant, which involved Keppel Seghers.

This is typically a contract between a public sector agency and a private party, where the private party takes on significantly more financial, technical and operational risk in the project.

Minister for the Environment and Water Resources Vivian Balakrishnan said: "The way we have organised our water supply system has got several lessons for many other countries.

"More recently, we've used public private partnerships, or PPP, for short, to involve the private sector in the desalination as well as the production of NEWater, so our companies like Hyflux, Sembcorp and Keppel Corp, have entered into contracts with PUB.

"These are complicated contracts and I'm not saying that they are easy to execute but if done properly, it provides an avenue to involve the private sector ingenuity, latest technology as well as commercial discipline in order to produce water more efficiently, and ultimately, at an affordable rate for our consumers".

Another advantage of PPPs is it allows local companies to build up a track record.

This gives them a competitive edge when they bid for contracts overseas.

These are just some of the main reasons for Singapore's success in the PPP model and why it is attracting interest from other countries.


Another $140m for water technology research

Extra funding meant to further spur quest for sustainable water solutions: Tharman
Lynn Kan Business Times 5 Jul 11;

(SINGAPORE) Water technology research here will get a further $140 million fillip from the National Research Foundation (NRF), to make its total budget $470 million.

Deputy Prime Minister Tharman Shanmugaratnam yesterday announced that the funding on top of the $330 million committed in 2006 is meant to further spur the industry's growth.

Singapore has targets to grow the sector's value-add contribution from $500 million in 2003 to $1.7 billion by 2015, and double jobs in the sector to 11,000.

The guardian of the earmarked research funding is the specialised Environment and Water Industry Programme Office (EWI), set up in 2006 to help get breakthrough research solutions off the ground.

The EWI has to date funded 64 R&D projects, three start-ups, six research centres and 38 scholarships.

Said the EWI: 'All of these projects are in different stages of development, ranging from fundamental research to demonstration plants close to commercialisation. Funding of these projects is a continual process and we are happy to receive the top-up of $140 million to expand the budget for R&D.'

At the opening ceremony of the Singapore International Water Week (SIWW) last night, Mr Tharman emphasised the importance of investing in new water technologies to urban living environs.

'We have to continue investing in technology and R&D aimed at developing sustainable water solutions - even if this means taking a long-term view, as the gestation periods can be long. And the payoffs to new technologies are sometimes realised only after a considerable amount of time,' he said.

Mr Tharman also urged public sector, academia and industry players to forge closer collaborations to hit upon the right solutions for urban eco-systems.

'By working across boundaries - of geography between cities, of technologies across sciences, and of knowledge across academia, the public sector and industry - we can potentially fast-track the development of solutions at a lower total cost, and make the challenge less daunting for everyone,' he said.

Mr Tharman highlighted some of such partnerships which have been around in Singapore for some years.

One of the latest efforts is the Singapore-Delft Water Alliance, a partnership between the National University of Singapore (NUS), consultancy Deltares and national water agency PUB.

The Water Alliance combines perspectives from academics and the public sector to carry out research. Tomorrow, it opens its new Aquatic Science Centre, which will conduct research as well as encourage the public to interact with scientists.

Research centres have also been set up here by 23 companies, among whom are GE Water, Siemens Water Technologies, Toray and Hyflux. These undertake research in 'close collaboration with our universities and public sector agencies', he said.

This year's (fourth) SIWW is the largest since the event started in 2008, with over 600 companies exhibiting at the Water Expo.

Last year, SIWW welcomed over 14,000 trade delegates from over 110 countries. Altogether, more than $2.8 billion in projects and investments were secured at last year's event.

PUB to set up centre for water-linked problems
Feng Zengkun Straits Times 5 Jul 11;

A NEW centre that can plug water-related problems faster - from floods to burst pipes and damaged treatment plants - will be set up next year.

The project by national water agency PUB and home-grown company ST Electronicsis expected to be ready in the second half of next year.

While both PUB and ST Electronics declined to reveal the location and cost of the centre, what is known is that its staff will be able to monitor the water-supply network, treatment plants and flood- monitoring systems all at the same time.

Once a problem is identified, field teams will be sent to the site, with updates of the shortest route obtained via Global Positioning System and live traffic feeds.

They will also be given equipment to transmit video and sound back to the centre. 'This will enable the officers to make more accurate decisions based on live information from the ground,' said an ST Electronics spokesman.

Last month, intense rain caused the worst flood seen here this year. The perceived increase in the number of floods in the past year has also led some to question if government agencies were up to the task of solving the problem.

The Government has said it will speed up improvement works in flood-prone areas. It also appointed a panel of 11 local and foreign experts to look into the drainage system and flood prevention measures.

PUB said the new centre was not in response to the recent floods but is part of a larger, ongoing project called the Intelligent Water Management System which includes a previously announced SMS flood alert system.

PUB's assistant chief executive of operations Tan Yok Gin said it was too early to comment on how much time the centre would save in handling problems.

The centre taps existing infrastructure such as water sensors in drains and canals that signal possible floods, and automated meter readers and mechanisms that monitor water use.

'We've already built up the hardware, now we're looking at ways to combine the different systems to increase our efficiency,' said Mr Tan.

Currently, an employee who wants to access different data has to log into multiple systems. For example, for water leaks, he would have to check which pipe has been damaged, which households or firms are supplied by the pipe, and then alert the appropriate department to notify the affected people.

The centre will house the different systems under one roof at first. The data sets will be integrated into a single system at a later stage.

The ST Electronics spokesman said the centre could be replicated in other cities.

The company's president Lee Fook Sun said increasing urbanisation was putting stress on infrastructure in cities worldwide.

The United Nations has estimated that 70 per cent of the world's population will live in cities by 2050, up from 50 per cent today.

'Centres like this can help them remain clean and secure,' Mr Lee said.

Singapore has hand in new WHO guidelines on drinking water
Grace Chua Straits Times 5 Jul 11;

THE World Health Organisation (WHO) unveiled a new set of guidelines on drinking water quality here yesterday - with Singapore playing a role in the drafting of the document.

The Republic lent its water management expertise, including desalination experience, to the drafting of the document.

It provided an expert and hosted three technical meetings to hammer out the fourth edition guidelines, which were released yesterday on the first day of Singapore International Water Week (SIWW).

Many countries, including Singapore, use the WHO document as the basis when they set their national standards and regulations on water.

The guidelines, meant for regulators and water utility companies, describe ways to keep water safe and the main risks to safe drinking water.

On desalination, they offer recommendations for treating and storing the desalinated water.

The WHO's decision to launch the guidelines - last updated in 2004 - at the SIWW reflects the event's growing stature.

Singapore's involvement in the drafting of the document also reflects the recognition it has earned for its water management expertise.

Singapore's contribution to the WHO document stems from a cooperation agreement it signed with the global public health organisation in 2007 to share its water expertise.

Professor John Fawell, an independent expert on the WHO committee that drew up the guidelines, said yesterday that Singapore's involvement 'has been very significant'.

Completion of the document would not be possible, he said, without experts like National University of Singapore toxicologist Ong Choon Nam and others from national water agency PUB.

Desalination, which supplies about 10 per cent of water here, is a key component of the Republic's water strategy. The first desalination plant in Tuas opened just six years ago and the ground-breaking for a bigger second plant takes place today.

More countries, such as Australia and Saudi Arabia, are also turning to desalination to meet their water needs.

The WHO guidelines launched yesterday also cover risks such as climate change and contamination by pharmaceutical drugs.

At least 884 million people around the planet do not have access to safe drinking water, and another two million die every year of water-borne diarrhoeal illnesses, said WHO coordinator Robert Bos.

The new guidelines provide the most help to these vulnerable groups, he said.

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Sea Turtle Smugglers Hooked in Bali

Made Arya Kencana Jakarta Globe 5 Jul 11;

Denpasar. Maritime police arrested three men on Monday as they allegedly attempted to smuggle 18 live green sea turtles into Bali, where a taste for illegal turtle meat is supporting an underground trade, police said.

Police, noticing some “unusual unloading activities” from their patrol boat, approached the men as they reportedly offloaded the endangered reptiles onto a beach at Tanjung Benoa Bay.

Three men — Gede Kole, 30, Gusti Ngurah Datia, 35, and Nyoman Sugira, 44 — were arrested and charged with wildlife smuggling, police said.

A fourth man, identified as Sudir, fled the scene in the boat.

“Our priority was to rescue the turtles first,” said Sr. Comr. Agus Duta, head of Bali Police’s maritime division.

“As for the fugitive, we’re on his trail.”

The men face up to five years in prison and fines totaling Rp 100 million ($11,700), Argus said.

According to Agus, the men claimed to know nothing about the turtle’s eventual destination.

It is also unknown if there were more turtles still on the boat when Sudir fled, Agus said.

“They all claim they were hired expressly to unload the turtles from the ship,” he said. “They say they don’t know anything more than that.”

The demand for live sea turtles has given rise to a black market in Bali, where animals the size of those seized can fetch prices as high as Rp 5 million a head, said Tamen Sitorus, head of the Bali Natural Resources Conservation Agency (BKSDA).

In 1999, the government passed a nationwide ban on the sea turtle trade.

But high demand drove the practice underground, where animal traffickers trap live turtles off the coasts of Sulawesi and East Java to smuggle them into Bali.

The turtles were commonly sacrificed in traditional Balinese Hindu ceremonies.

In 2009, Bali Governor I Made Mangku Pastika proposed an annual quota of 1,000 sea turtles for sacrificial ceremonies. The measure was shot down.

Police believe this shipment of turtles was destined for Bali’s dinner plates.

“We suspect the turtles were headed for restaurants here where they illegally serve turtle meat,” Agus said.

The BKSDA estimates that the turtles were at least 10 years old and were caught off the coast of Sulawesi.

Green sea turtles can live up to 80 years in the wild.

The agency released 16 of the reptiles back into the sea on Monday afternoon. The remaining two turtles were sent to the agency’s turtle conservation center on Serangan Island, where they will be used as evidence against the alleged smugglers.

Nationwide, the number of smuggling cases remains high, in spite of the nationwide ban, Tamen said.

In May, officers seized 150 kilograms of turtle meat aboard a boat hailing from Madura Island in East Java.

In January, police foiled an attempt to smuggle in 38 live turtles aboard another boat from Madura Island.

And in November last year, Bali police seized a shipment of 87 live green sea turtles being smuggled into the resort island from Sulawesi.

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Indonesia: Illegal Monkey Trade in Bali Raises Concerns

Made Arya Kencana Jakarta Globe 4 Jul 11;

Denpasar. Bali is fast becoming a key hub in the illegal primate trade, with more than 200 endangered Javan lutungs trafficked through the resort island every month, animal rights activists claimed on Sunday.

In a protest at Denpasar’s Badjra Sandhi monument, activists from the group ProFauna brandished posters reading “Stop the Trade in Primates” and “We Are Not for Sale.”

Rosek Nursahid, chairman of the nongovernmental organization, said most of the endangered primate species being traded both within the country and overseas were caught in protected habitats, thus threatening the survival of many species in the wild. He said that Bali was growing in prominence as a trading hub for lutungs, which he claimed were poached from the Baluran and Meru Betiri national parks in Banyuwangi district in neighboring East Java.

More than 200 of the primates are trafficked through Bali each month, mostly for human consumption, according to ProFauna, citing research it has done.

“This is a dire threat to the survival of the species,” Rosek said. “Their meat is widely believed to be a cure for asthma, although there is no scientific evidence to support this view at all. It’s also considered to go well with the local moonshine.”

He urged a massive public awareness campaign by the Bali administration to help stop the trade in lutungs. Rosek cited the success of a similar campaign to save the green sea turtle, which had previously been threatened by poaching for food and as sacrificial animals in Balinese Hindu rites.

“We hope the Balinese authorities can do for the lutungs what they did for the turtle some years ago, when they ended the trapping and hunting of the animal for food,” Rosek said.

In addition to the lutung, he added, other species facing extinction due to the illegal wildlife trade included the Sumatran orangutan, the silvery gibbon and the Javan slow loris. All three are listed in Appendix I of the Convention on International Trade in Endangered Species, which outlaws their trade. The silvery gibbon and Javan slow loris are classified as vulnerable species, while the orangutan is classified as critically endangered — just one step away from extinction.

Rosek said that despite the prohibition, these primates were being illegally exported to the Middle East, Taiwan, Hong Kong Malaysia and Singapore, fetching from Rp 200,000 ($23) for a lutung or loris to Rp 1 million for a gibbon and Rp 2 million for an orangutan.

“Our concern is that once they arrive in these importing countries, the animals are ‘laundered’ for sale in the legal pet trade, which is where the dealers make their profit,” he said.

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Rhino poaching surge continues in 2011

WWF 4 Jul 11;

Nearly 200 rhinos have been killed in South Africa during the first half of the year, according to statistics from the national parks department. The rate of poaching if not curbed could exceed 2010 levels when a record 333 rhinos were killed in the country.

South Africa has lost at least 193 rhinos during the first six months of 2011 with Kruger National Park continuing to be hardest hit. The world famous safari destination has already lost 126 rhinos to poaching this year in addition to 146 killed there in 2010.

“Poaching is being undertaken almost without exception by sophisticated criminals, sometimes hunting from helicopters and using automatic weapons,” says Dr. Joseph Okori, WWF’s African Rhino Programme Coordinator. “South Africa is fighting a war against organized crime that risks reversing the outstanding conservation gains it made over the past century.”

South Africa is home to the largest populations of African rhinos, including white rhinos and critically endangered black rhinos.

In response to the recent poaching crisis, law enforcement measures have been increased resulting in 123 arrests and six successful convictions so far in 2011. Last year South African authorities arrested a total of 165 suspected poachers and convicted four. Judicial proceedings are ongoing for many of the suspects.

“We are pleased to see more successful convictions of poachers,” said Dr. Morné du Plessis, CEO of WWF South Africa. “Applying strict penalties for wildlife crimes such as rhino poaching will demonstrate the South African government’s commitment to maintaining this important part of the country’s heritage.”
In June, neighbouring Swaziland lost its first rhino to poaching in nearly 20 years sparking fears that the crime wave could be spreading. Authorities in Swaziland arrested three suspects within days of the killing, but have since released them on bail.

WWF opposes the granting of bail to poaching suspects due to the gravity of their crimes and their high flight risk. Suspects at large continue to pose a threat to rhinos and can cause delays to judicial proceedings.

“We cannot allow poaching to proliferate across rhino range countries,” Dr. Okori says. “Swift prosecutions of wildlife crimes and strict sentences for perpetrators will serve as a deterrent to potential criminals. Poachers should be shown no leniency.”

Rhino poaching is being fueled by demand for horns in Asia, where they are highly valued for traditional medicine, although rhino horn has no scientifically proven healing properties.

“The poaching surge shows no sign of abating,” says Tom Milliken, Elephant & Rhino Programme Coordinator with TRAFFIC, the wildlife trade monitoring group. “Only a concerted international enforcement pincer movement, at both ends of the supply and demand chain, can hope to nip this rhino poaching crisis in the bud.”

WWF and TRAFFIC provide technical assistance to wildlife management authorities and support greater inter-agency law enforcement cooperation. In May WWF financed the purchase of an ultralight aircraft for rangers in South Africa’s KwaZulu-Natal province. TRAFFIC is a joint programme of WWF and IUCN.

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Sulphur from Chinese power stations 'masking' climate change

Research reveals decade of global warming from China's coal power stations has partly been offset by 'cooling' effect of sulphur pollution
Damian Carrington 4 Jul 11;

The huge increase in coal-fired power stations in China has masked the impact of global warming in the last decade because of the cooling effect of their sulphur emissions, new research has revealed. But scientists warn that rapid warming is likely to resume when the short-lived sulphur pollution – which also causes acid rain – is cleaned up and the full heating effect of long-lived carbon dioxide is felt.

The last decade was the hottest on record and the 10 warmest years have all occurred since 1998. But within that period, global surface temperatures did not show a rising trend, leading some to question whether climate change had stopped. The new study shows that while greenhouse gas emissions continued to rise, their warming effect on the climate was offset by the cooling produced by the rise in sulphur pollution. This combined with the sun entering a less intense part of its 11-year cycle and the peaking of the El Niño climate warming phenomenon.

The number of coal-fired power stations in China multiplied enormously in that period: the electricity-generating capacity rose from just over 10 gigawatts (GW) in 2002 to over 80GW in 2006 (a large plant has about 1GW capacity).

But rather than suggesting that cutting carbon emissions is less urgent due to the masking effect of the sulphur, Prof Robert Kaufman, at Boston University and who led the study, said: "If anything the paper suggests that reductions in carbon emissions will be more important as China installs scrubbers [on its coal-fired power stations], which reduce sulphur emissions. This, and solar insolation increasing as part of the normal solar cycle, [will mean] temperature is likely to increase faster."

Prof Joanna Haigh, at Imperial College London, commented: "The researchers are making the important point that the warming due to the CO2 released by Chinese industrialisation has been partially masked by cooling due to reflection of solar radiation by sulphur emissions. On longer timescales, with cleaner emissions, the warming effect will be more marked."

The cooling effect of sulphur pollution on climate has long been recognised by scientists studying volcanic eruptions, which have, for example, caused failed crops and famines in the past. Sulphur dioxide forms droplets of sulphuric acid in the stratosphere, which increases the reflection of the Sun's heat back to space, cooling the Earth's surface.

The effect also explains the lack of global temperature rise seen between 1940 and 1970: the effect of the sulphur emissions from increased coal burning outpaced that of carbon emissions, until acid rain controls were introduced, after which temperature rose quickly. Some have even proposed sulphur dioxide could used to geoengineer the planet by deliberately injecting millions of tonnes into the atmosphere to combat warming.

The new study, published in the Proceedings of the National Academy of Sciences on Monday, analysed possible reasons for the flat 1998-2008 temperature trend using climate models and concluded that it was unlikely to be due simply to the random variation inherent in the planet's climate system. Instead it found the effect of sulphur, the sun and El Niño dominated, with the El Niño climate phase peaking in 1998 – the hottest year ever recorded – then moving into a phase dominated by its cooler mirror image, La Niña. The scientists ruled out changes in water vapour or carbon soot in the atmosphere as significant factors.

They emphasised the rapid increase in coal burning in Asia, and in China in particular, noting that Chinese coal consumption doubled between 2002 and 2007: the previous doubling had taken 22 years.

Michael E Mann, at Pennsylvania State University and not part of the research team, said the study was "a very solid, careful statistical analysis" which reinforces research showing "there is a clear impact of human activity on ongoing warming of our climate". It demonstrated, Mann said, that "the claim that 'global warming has stopped' is simply false."

Asia Pollution Blamed For Halt In Warming: Study
Gerard Wynn PlanetArk 5 Jul 11;

Smoke belching from Asia's rapidly growing economies is largely responsible for a halt in global warming in the decade after 1998 because of sulphur's cooling effect, even though greenhouse gas emissions soared, a U.S. study said on Monday.

The paper raised the prospect of more rapid, pent-up climate change when emerging economies eventually crack down on pollution.

World temperatures did not rise from 1998 to 2008, while manmade emissions of carbon dioxide from burning fossil fuel grew by nearly a third, various data show.

The researchers from Boston and Harvard Universities and Finland's University of Turku said pollution, and specifically sulphur emissions, from coal-fueled growth in Asia was responsible for the cooling effect.

Sulphur allows water drops or aerosols to form, creating hazy clouds which reflect sunlight back into space.

"Anthropogenic activities that warm and cool the planet largely cancel after 1998, which allows natural variables to play a more significant role," the paper said.

Natural cooling effects included a declining solar cycle after 2002, meaning the sun's output fell.

The study said that the halt in warming had fueled doubts about anthropogenic climate change, where scientists say manmade greenhouse gas emissions are heating the Earth.

"It has been unclear why global surface temperatures did not rise between 1998 and 2008," said the study published in the Proceedings of the National Academy of Sciences of the United States.

A peak in temperatures in 1998 coincided with a strong El Nino weather event, a natural shift which brings warm waters to the surface of the Pacific Ocean every few years.

Subsequent years have still included nine of the top 10 hottest years on record, while the U.N. World Meteorological Organization said 2010 was tied for the record.

A U.N. panel of climate scientists said in 2007 that it was 90 percent certain that humankind was causing global warming.


Sulphur aerosols may remain in the atmosphere for several years, meaning their cooling effect will gradually abate once smokestack industries clean up.

The study echoed a similar explanation for reduced warming between the 1940s and 1970s, blamed on sulphur emissions before Western economies cleaned up largely to combat acid rain.

"The post 1970 period of warming, which constitutes a significant portion of the increase in global surface temperature since the mid 20th century, is driven by efforts to reduce air pollution," it said.

Sulphur emissions are linked to coal consumption which in China grew more than 100 percent in the decade to 2008, or nearly three times the rate of the previous 10 years, according to data from the energy firm BP.

Other climate scientists broadly supported Monday's study, stressing that over longer time periods rising greenhouse gas emissions would over-ride cooling factors.

"Long term warming will continue unless emissions are reduced," said Peter Stott, head of climate monitoring at Britain's Met Office.

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