Global warming is affecting Africa more than the industrialised world despite being the inhabited continent least to blame for the greenhouse effect.
A study by scientists at Britain's Hadley Centre has found that the tell-tale signature of global warming is significantly stronger in Africa than in other continents such as Europe and America.
The researchers believe that industrial pollution, which emits the carbon dioxide that exacerbates the greenhouse effect, also offers some localised protection against climate warming.
But because Africa is not as industrialised as most other continents it does not produce the pollutants, such as aerosol particles, that can help to shield against the sun, said Peter Stott, a climate researcher at the centre. "While Africa is not a region that has been pumping out carbon dioxide, it's still seen a clear warming signal, Dr Stott said. "In the industrial countries part of the warming has been offset by cooling due to aerosols."
The latest research by the Hadley Centre, which is part of the Meteorological Office in Bracknell, Berkshire, has shown that the signals of global warming are now so strong that they can be measured over individual continents as opposed to being detectable solely over the entire globe.
The study compared temperature rises since the beginning of the last century over six continents with predictions made by computer models designed to forecast climate changes from global warming. Some scientists have suggested that any warming is likely to be caused by natural phenomena, such as volcanoes or changes in solar energy reaching the Earth, rather than man-made emissions of carbon dioxide.
However, Dr Stott said that the latest findings support the view of the majority of climate researchers who believe that global warming is both real and the result of rising levels of carbon dioxide pollution.
"The continental warming of the past few decades cannot be explained by natural factors such as solar changes, volcanoes or natural variability," Dr Stott said. "But once we factor in the effects of human activity, we find we can explain the warming of the past few decades is largely due to emissions of greenhouse gases such as carbon dioxide.
He added: "Now we have gone a stage further and shown that the same thing is happening on the scale of continents."