(Repeats, fixing date)

By Alister Doyle, Environment Correspondent

POZNAN, Poland, Dec 2 (Reuters) - Soot is darkening ice in the Arctic and speeding a melt that could make the ocean around the North Pole ice-free in summer well before 2050, experts said on Tuesday.

The experts said the fight against warming in the Arctic should be re-directed to focus more on cutting the industrial pollution from soot, ozone and methane in Europe, North America and Russia to try to prevent the ice disappearing.

Soot or black carbon darkens the ice and makes it soak up more heat, accelerating a melt compared to reflective snow and ice. Methane comes sources including oil and gas and agriculture while ozone is formed from industrial pollutants.

"Reductions in these pollutants would have a greater impact" in the next two decades than curbing emissions of the main greenhouse gas -- carbon dioxide -- according to scientists on the sidelines of 187-nation U.N. climate talks in Poland.

The Arctic is warming at twice the rate of the rest of the world and ice shrank to a record low in 2007, leading to worries that it could pass a point of no return.

"The Arctic sea ice may already have passed a 'tipping point'," said Pam Pearson, an Arctic pollution expert at the Climate Policy Center who presented the findings. "An ice-free summer Arctic is now possible well before 2050".

"Some scientists are arguing that it (the Arctic Ocean) could be (ice free) in summer within the next 10 to 20 years," said Bob Watson, a former head of the U.N. Climate Panel who chaired a presentation of the research in Poznan.

The three pollutants -- soot, ozone and methane -- linger in the atmosphere far less time than carbon dioxide, meaning cuts in emissions would have a quicker impact in cleaning the air.

The U.N. panel projected last year that it could be clear of ice by the end of the century. A thaw would threaten indigenous peoples and wildlife such as polar bears and seals.

"The question is: is all of the rapid melt of the Arctic ice in summer all due to human induced climate change or is part of it some natural cycle? We clearly have to understand it," Watson, now chief scientific advisor to the British Environment Ministry, told Reuters.

"This is not just a climate issue for the Arctic but for the globe as a whole," said Hanne Bjurstroem, the head of Norway's delegation, at the Dec. 1-12 climate talks on a new climate treaty.

A melt of the Arctic ice would warm the top of the globe and lead to warming further south. An ice-free Arctic would also make the region more accessible to oil and gas exploration and shipping.

-- For Reuters latest environment blogs click on: http://blogs.reuters.com/environment/ (Editing by Alison Williams)

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