Nations around the globe should aim to cut their greenhouse gas emissions by at least half by 2050, according to a draft text circulated at the UN climate talks in Copenhagen.

The draft accord indicates that wealthy nations would make major cuts over the next decade, leading the way to the wider goal of dropping global greenhouse gas emissions by 50 to 95 per cent worldwide over the next 40 years. Rich countries would cut emissions by 25 per cent to 40 per cent by 2020. In both cases, 1990 emissions would be used as the baseline year.

No financial terms were included in the draft, as they will be hammered out by 110 world leaders, including Prime Minister Stephen Harper and U.S. President Barack Obama, who will meet in the Danish capital next week.

"It's time to begin to focus on the big picture," said Yvo de Boer, the top UN climate official. "The serious discussion on finance and targets has begun."

Leaders hope to work out an agreement that will reduce greenhouse gas emissions and help poor nations deal with the effects or global warming -- from rising sea levels to reduced rainfall.

But it will likely be difficult for participants to agree on the massive financial commitments required for achieving that goal, which some analysts say could amount to US$150 billion per year.

Dale Marshall, of the David Suzuki Foundation, said the challenge is large, but achievable.

"It's always difficult when you're trying to get 190 countries to agree to a plan, but obviously the countries are all united around a cause which is that we have to find a solution to global warming," Marshall told CTV's Canada AM from Copenhagen.

The discussions come as a growing number of people dispute the science of climate change, pointing to leaked emails from within the scientific community that suggest statistics were fudged to prove a warming trend exists.

At a separate meeting in Brussels on Friday, British Prime Minister Gordon Brown and France's Nicolas Sarkozy agreed to contribute more than $3 billion a year to help poor nations battle the effects of climate change -- from rising sea levels to reduced rainfall.

The two leaders are trying to get other smaller European Union nations to chip in.

But the discussions taking place in Denmark on Friday were not without their problems.

China's Vice Foreign Minister He Yafei lashed out at Todd Stern, the top U.S. climate negotiator.

He said that Stern either "lacks common sense" or was "extremely irresponsible" for saying that no U.S. funding should be going to China.

Stern said that the U.S. doesn't consider China one of the neediest countries when it comes to determining financial aid.

The European Union said Friday that it would push its 2020 target to a 30 per cent cut, up from a 20 per cent cut. The move was seen as a method of pushing other wealthy nations to deepen their emission-cutting pledges next week. And it is a conditional offer, dependent on stronger commitments by the U.S. and Canada.

Earlier Friday, street protests broke out in Copenhagen, with police arresting at least 40 people for demonstrations linked to the ongoing climate summit.

Intensity has been building at the two-week climate gathering as it approaches the final stage of talks, when world leaders will arrive to focus on hammering out a deal to control greenhouse gases.

On Friday about 200 people took to the streets of the Danish capital, banging drums and shouting chants such as "Mind your business, this is our climate!" The Associated Press reports.

A police spokesperson said the detentions were a preventative measure to avoid disorder. No violence was reported.

With files from The Associated Press