OSLO, Sun Oct 26,(bdnews24.com/Reuters) - Backers of extreme technologies to curb global warming advocate dumping iron dust into the seas or placing smoke and mirrors in the sky to dim the sun. But, even though they are seen by some as cheap fixes for climate change when many nations are worried about economic recession, such "geo-engineering" proposals have to overcome wide criticism that they are fanciful and could have unforeseen side effects. "We are at the boundaries, treading in areas that we are not normally dealing with," said Rene Coenen, head of the Office for the London Convention, an international organization that regulates dumping at sea. The London Convention, part of the International Maritime Organization, will review ocean fertilization at a meeting this week. Among those hoping for approval for tests is Margaret Leinin, chief science officer of California-based Climos, a company that is looking at ways to use the oceans to soak up greenhouse gases. "The world has not been able to get carbon emissions under control" Leinin said. "We should look at other options." Climos is seeking to raise money to test adding iron dust to the southern ocean to spur growth of algae that grow by absorbing heat-trapping carbon dioxide from the air. When algae die, they fall to the seabed and so remove carbon. Other short-cut ideas include spraying a smoke of tiny particles of pollutants into the sky to dim sunlight, or even deploying a vast thin metallic barrier in space, with 100 space shuttle flights, to deflect the sun's rays. "CHEMICAL SOUP" The U.N. Climate Panel has said world greenhouse gas emissions from human activities, mainly burning fossil fuels, rose 70 percent between 1970 and 2004. But it said that fertilizing the oceans or dimming the sun "remain largely speculative and unproven, and with the risk of unknown side-effects." "More evidence has been coming in since then, but it's far from making a reliable case for geo-engineering," said Terry Barker, head of the Cambridge Center for Climate Change Mitigation Research and one of the leading authors of the U.N. panel report. The seas are already suffering enough from a "chemical soup" of pollution from humans, he said. "There's no need to add to the mess." With fears of recession and amid the deepest financial crisis since the 1930s, some governments may find cheap geo-engineering attractive compared with reducing carbon emissions. "It would be shortsighted," Baker said. Last year, the London Convention said that "knowledge about the effectiveness and potential environmental impacts of ocean iron fertilization currently was insufficient to justify large-scale operations." Those doubts were "still valid," the Convention's Coenen said. Firms such as Australia's Ocean Nourishment, Atmocean in New Mexico and Climos are working on varying sea-based projects. Another start-up, Planktos, indefinitely suspended operations in February after failing to raise cash. Some like Climos hope that sucking carbon into the ocean, if it works, could qualify for credits as carbon trading. "It is possible to design experiments to avoid harm to the oceans," said Leinin. Climos wants to test iron fertilization in the southern ocean, at the earliest in January 2010 in a test that could $15-20 million, she said. If it works, Leinin said it could be one of the cheapest ways to combat global warming. LESSER RISK Among objections are that carbon makes water more acidic and could undermine the ability of shellfish, crabs or lobsters to build shells. That in turn could disrupt the marine food chain. Backers of geo-engineering say the risks are slight compared to far bigger disruptions from climate change, stoked by human emissions of greenhouse gases, which could lead to heatwaves, floods, droughts, more disease or rising seas. "We are already bludgeoning nature," said Victor Smetacek, a professor at the Alfred Wegener Institute in Germany, who is planning an iron sulphate fertilization experiment off Antarctica in early 2009. His institute will cooperate with India to disperse 20 tonnes of iron sulphate near South Georgia over 300 sq kms (115 sq miles). "Iron has a very positive effect. Added to the ocean it's like water in the desert," he said. "We don't have space to store the carbon we are producing on land," he said of proposals including planting more forests. They will study how far algae grow and absorb carbon. The extra algae, as food, might help a recovery of stocks of shrimp-like krill, a species on which penguins and whales depend. Among other schemes, Nobel chemistry prize winner Paul Crutzen has floated the idea of blitzing the upper atmosphere with sulfur particles to reflect some sunlight back into space. "The price is not a factor...it's peanuts," he told Reuters in Nicosia earlier this month. "The cost has been estimated at some 10, 20 million U.S. dollars a year." Similar smoke is released naturally by volcanic eruptions, such as Pinatubo in the Philippines in 1991 or Tambora in Indonesia in 1815. The Indonesia eruption led to a "year without a summer," according to reports at the time. Other proposals reviewed by the UN Climate Panel include installing a metallic screen covering a 106 sq km (40.93 sq mile) patch of space 1.5 million kms (930,000 miles) away from earth in the direction of the sun. The 3,000-tonne structure could be put in place over 100 years by 100 space shuttle flights. "The cost has yet to be determined," the panel said. Another idea is to spew more sea spray into the air -- a natural process caused by waves. The plan would make low-level clouds slightly whiter and bounce solar rays back into space. Advantages are that the only ingredient is sea water, and production could be turned off. But the UN panel said "the meteorological ramifications need further study."