Scientists and government officials are finishing a much-awaited report expected to say that climate change is real, serious and that human influence on it is undeniable.

The Intergovernmental Panel on Climate Change will release the report on Friday at a news conference in Paris, although a simultaneous one will be held in Ottawa.

"The climate's changing and it's going to change some more no matter what we do -- particularly if we keep consuming so many fossil fuels," Michael McCracken, the Climate Institute's chief scientist, said Monday in Washington.

"They say 'think globally, act locally', so we're hoping that it will convince people ... that climate change is real and that we have a responsibility for much of it, and that we really do have to make changes in how we live," Kenneth Denman told reporters in Paris.

He's co-author of the report and a senior scientist at the Canadian Centre for Climate Modelling and Analysis.

Scientists have been tightlipped about the contents of the report. However, they say it is both more specific and more sweeping than the organization's previous efforts.

A final review of the draft began on Monday. IPCC officials will issue a policy-maker's summary of the full report after they finish days of secret word-by-word editing.

Rajendra Pachauri, director-general of the Tata Energy Research Institute, chairs the IPCC. He said in Paris that the report would make "significant advances" over the last one issued in 2001.

The new report will also address gaps in the past assessment and contribute new knowledge about climate change, he said.

The report draws on research by 2,500 scientists, including skeptics and industry researchers, from more than 130 countries.

Rising seas?

Some scientists say that within a century, rising sea levels could swallow most of Prince Edward Island and threaten cities like Halifax and Vancouver. However, others say that's an unlikely scenario.

Early drafts of the document forecast that by 2100 the sea level will rise between 12.7 and nearly 58.5 centimetres.

Many top scientists reject those figures. A study published in the peer-review journal Science this month predicted an increase of nearly 51 to 140 centimetres by 2100.

Other climate experts, including NASA's James Hansen, predict even bigger sea level increases.

Some critics worry that the IPCC scientists did not take into account the recent melt-off of big ice sheets in Greenland and Antarctica.

The melting ice sheets have surprised some scientists, who don't know how to predict the effects in their computer models.

Their forecasts considered only how much the sea level would rise because of melting glaciers -- which are different from ice sheets -- and the physical expansion of water as it warms.

"The whole question of how much melting will take place in Greenland and Antarctica is difficult to put numbers exactly on," Gordon McBean, a climate change scientist in London, Ont.

While some fear this will mean the world's coastlines will be flooded earlier than thought, others believe the ice melt is temporary.

The debate matters to policy makers because without accurate estimates, they won't know how to plan coastal development.

This contentious debate is expected to dominate discussions in Paris.

A German scientist said documents such as this one tend to underestimate risk.

The prediction that the IPCC is considering is "obviously not the full story because ice sheet decay is something we cannot model right now, but we know it's happening," Stefan Rahmstorf told The Associated Press.

Rahmstorf, a physics and oceanography professor at Potsdam University in Germany, says, "In a way, it is one of the strengths of the IPCC to be very conservative and cautious and not overstate any climate change risk."

The report must be unanimously approved by 154 governments, including the United States and oil-rich countries such as Saudi Arabia.

This installment of the report will not address how global warming's impacts or how to tackle the problem. Those sections will come later this year.

However, the Australian newspaper The Age reported on Tuesday that towards the end of this century, global warming will cause food and water shortages that would affect hundreds of millions of people.

Countries in Africa, for example, or like Bangladesh would be most affected because they would be the least able to cope with more coastal damage and drought, according to an early draft the newspaper obtained.

With a report from CTV's David Akin and files from The Associated Press