By Roger Harrabin
Environment analyst, BBC News
Rich nations must do far more to help poor countries cope with the consequences of climate change, an influential report is expected to say.
Refugees from floods and droughts are expected to increase
The review will also say emissions need to be cut now, the BBC has learned.
The author, former World Bank chief economist Sir Nicholas Stern, argues it will be cheaper to act now rather than try to deal with the problem later.
UK Chancellor Gordon Brown commissioned Sir Nicholas to examine the economics of climate change and its impacts.
Mr Brown and the UK Prime Minister, Tony Blair, hope the findings will end a long-running debate between economists about the best way to tackle global warming.
Some, mainly free-market economists from the US, say there is uncertainty over how bad climate change will be. Therefore, they believe, money should not be wasted on costly measures to curb emissions. They think the best solution is to invest the money in adapting to potential consequences.
The opposing view, supported by the UK and other EU nations, holds that emissions need to be cut as soon as possible.
Sir Nicholas will say that the West will also have to pay far more to help poor nations cope with the problems caused by carbon emissions.
Bangladesh is one nation that experts believe will be hardest hit by a warming world.
Climatologists say the country's rainy season will be compacted, resulting in more flooding during the monsoon season and intense droughts during longer summers.
Because Bangladesh is situated on low-lying ground, it is also expected to be hit by rising sea levels, experts warn.
Between 10-30 million people could be forced from their homes by the end of the century, say Bangladeshi government officials.
Environment Minister Jafrul Chowdhury expressed anger at the lack of international progress on tackling climate change.
"Our people will be helpless and homeless, but without any reason. We are not responsible for this," he told BBC News.
Mr Blair and Mr Brown hope the findings will work to unite international efforts to combat the impacts of climate change.
Sir Nicholas is expected to present his conclusions to the leaders of the world's wealthiest nations at a G8 climate meeting in Mexico at the beginning of October.