Africa is facing the greatest catastrophe in human history. Climate change represents a nightmare scenario for the future of the people of the world's poorest continent, according to the official preparing a top- level report which is due to land on the desks of Tony Blair and Gordon Brown in later this year.
Emerging analysis seen by the Stern Review into the economic impact of climate change suggests one of the worst affected places on the planet will also be the poorest.
Global warming could cause temperature rises double those elsewhere. The consequence would be dramatic declines in rainfall and a fall in crop yields that could make previous famines look like small tragedies. Desertification could accelerate around the Sahara. There are likely to be severe water shortages in many parts of the continent.
Diseases such as malaria, dengue fever and cholera may increase. As many as 67 million more people could be at risk of malaria epidemics by the 2080s. As a result, huge sections of the population may be set on the move.
The report, by Sir Nick Stern, head of Government Economic Policy, is due to be completed in October. The review is still in progress, but evidence given by the Hadley Centre, one of Europe's leading research bodies on climate change, predicts an average rise in global temperatures of between 2.4 to 5.4C.
But for Africa temperature rises over many areas will be double the global average. Sir Nick explained: "For example, under a high emissions scenario, global temperatures will rise by over 4C by the 2080s, but according to some models temperatures in Africa could rise by up to 7C in southern Africa and 8C in northern Africa - almost double the global average".
Some of the poorest parts of the continent will be the worst hit. "The interior of the continent and particularly the Sahara and southern Africa will be most seriously affected, experiencing the most extreme temperature rises coupled with severe reductions in rainfall," a draft says.
"Africa is already vulnerable to climate variability," it continues. "Small rises in temperature and reductions in rainfall could 'tip the balance' and lead to severe water shortages and reductions in crop yields". These could fall by as much as 30 per cent by the 2050s.
Sir Nick's remarks comes on top of one by the charity Christian Aid, which suggested that up to 182 million people in sub-Saharan Africa could die of diseases directly attributable to climate change by the end of the century. But where the aid agency's report seemed to be based on extrapolations of existing figures - sources were not given - the submissions to the Stern Review are based on well-sourced blue-chip scientific evidence.
The impact of the change will be difficult to handle and it will be potentially very long lasting. "It is very serious," Sir Nick said.
Two things give his conclusions added urgency, he said: the scientific evidence on global warming is strengthening daily, and there are risks over and above those that are usually considered. For example, the release of methane from the permafrost could bring an acceleration that is not factored into many existing models on climate change.
The disproportionate impact on Africa will be for a combination of reasons. Global warming will be greater over land than over sea because land retains heat more than water. But it will also be greatest in the tropics and in low altitudes. There is also increasing evidence that it will be particularly hit by the effect of vertical rises and falls in air currents.
"West Africa will get drier and east Africa will get wetter," Sir Nick said. However, that will not necessarily be good news for drought-hit areas such as Ethiopia. Observations in India already show areas getting twice the rainfall in half the number of days, causing storms and floods and even greater soil erosion.
"We can provide resources to help people adapt to the inevitable impacts of climate change in the coming years," concludes Sir Nick. "But if we act now, and strongly, to mitigate climate change, it is likely that we could reduce the risks of these scenarios while continuing economic growth."
Main areas of concern
* Temperature rises over many areas will be greater than the global average. The general predicted rise is 4C by the 2080s. But temperatures could rise to 7C in southern Africa and 8C in northern Africa - almost double the global average
* Significant changes in rainfall could be experienced across the continent, with the area around the Sahara and in southern Africa
* Desertification is likely to increase around the Sahara, causing populations to move.
* Rising temperatures, widespread water stress, increased frequency and severity of droughts and floods, and rising sea levels will severely damage progress on development goals in Africa.
* Cereal crop yields could fall between 10 to 30 percent by the 2050s compared to 1990 levels.
* Heat waves will bring increased injuries and death.
* Vector- and water-borne diseases such as malaria, dengue fever and cholera may increase.An additional 67 million people in Africa could be at risk of malaria epidemics by the 2080s.
Greenhouse gases must be curbed and help must be given to vulnerable Africans to adapt to the new climate conditions. The cost of climate-proofing current investment plans will be between $10bn and $40bn.