By Jeremy Lovell

LONDON, Nov 19 (Reuters) - Britain will study whether it can commit to cutting its carbon emissions by as much as 80 percent by 2050, Prime Minister Gordon Brown said on Monday in his first major speech on the environment since taking office this year.

Brown has been challenged to take a strong stance on global warming by an opposition Conservative Party that increasingly stresses environmentalism. His popularity has sunk in recent weeks to the lowest since he took over from Tony Blair in June.

Brown's government published a draft Climate Change Bill a week ago committing to a 60 percent cut in carbon dioxide emissions by 2050, but environmentalist groups have said it should look at even deeper cuts.

The government will set up an independent committee to study whether it should commit to even deeper cuts of 80 percent.

"Our vision has one overriding aim: holding the rise in global average temperature to no more than 2 degrees centigrade. This requires global greenhouse gas emissions to peak within the next 10 to 15 years and be cut at least by half by 2050," Brown told a meeting hosted by environment group WWF.

"A global carbon market is at the heart of our approach -- not the old way of rigid regulation but the modern way: harnessing the power of the market to set a global price for carbon," he added.

TOUGH CURBS

Brown said it was vital that the world's developed nations, who have produced most of the climate changing carbon gases, take the lead in committing to tough curbs on their emissions -- including the United States which has so far refused.

He also endorsed the European Union's commitment in March this year to getting 20 percent of primary energy from renewables by 2020 -- a goal that some elements of the government have tried to back away from.

Scientists say average world temperatures will rise by between 1.8 and 4.0 degrees Celsius this century due to burning fossil fuels for power and transport, causing floods, droughts, famines and putting millions of lives at risk.

But while noting the scale and urgency of the crisis, Brown also underscored the job and business opportunities it offered.

"Globally, the overall added value of the low carbon energy sector could be as high as 3 trillion dollars per year worldwide by 2050," he said. The industry could create 25 million new jobs, including a million in Britain.

The speech comes two weeks before U.N. environment ministers meet on the Indonesian island of Bali to try to launch a rapid round of negotiations on a successor to the Kyoto Protocol carbon cutting accord that expires in 2012. (Reporting by Jeremy Lovell; editing by Peter Millership)

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