By David Adam
    The Sydney Morning Herald

    Saturday 12 May 2007

    Climate change may have passed a key tipping point that could mean temperatures rising more quickly than predicted and it being harder to tackle global warming, research suggests.

    Scientists at Bristol University say a previously unexplained surge of carbon dioxide levels in the atmosphere in recent years is due to more greenhouse gas escaping from trees, plants and soils. Global warming was making vegetation less able to absorb the carbon pollution pumped out by human activity.

    Such a shift would worsen the gloomy predictions of the UN's Intergovernmental Panel on Climate Change, which warned last week that there is less than a decade to tackle rising emissions to avoid the worst effects of global warming.

    The prediction came as an equally stark warning was issued that global warming was contributing to increased conflict over dwindling resources.

    At the moment about half of human carbon emissions are re-absorbed into the environment, but the fear among scientists is that increased temperatures will reduce this effect. Wolfgang Knorr, a climate researcher at Bristol, said: "We could be seeing the carbon cycle feedback kicking in, which is good news for scientists because it shows our models are correct. But it's bad news for everybody else." Measurements of carbon dioxide in samples of air show a sharp increase since the turn of the century, with unusually high levels in four of the past five years. The spike does not seem to match the pattern of increased emissions from fossil-fuel burning, and can only be partly explained by natural events such as fires and weather phenomena including El Nino.

    Dr Knorr's team compared the high carbon dioxide measurements in the atmosphere for 2002-03 with simulations of how soils and plants, including trees, behave under different conditions. They found the extra carbon dioxide in the atmosphere could be accounted for by plants taking up less carbon because of unusually dry and hot conditions.

    Writing in Geophysical Research Letters, they say: "We find that the remarkable feature of the 2002-03 anomaly seems to be that climate fluctuations - not only related to El Nino and occurring across all latitudes - acted together to create an unusually strong out-gassing of CO2 of the terrestrial biosphere. Further research will be required to investigate if this fluctuation carries features of projected future climate change."

    The British Foreign Secretary, Margaret Beckett, warned on Thursday that climate change could spawn a new era of conflicts over water and other scarce resources. She said climate-driven conflicts were already under way in Africa. Underlying the Darfur crisis was a struggle between nomadic and pastoral communities for resources made more scarce through a changing climate.

    Speaking at the Royal United Services Institute in London on Thursday, Mrs Beckett quoted evidence that a similar conflict was brewing in Ghana where Fulani cattle herdsmen are reportedly arming themselves to take on local farmers in a confrontation over water and land as climate change expands the Sahara Desert.

    The Foreign Secretary said the Middle East - with 5 per cent of the world's population but only 1 per cent of its water - would be particularly badly affected, with Saudi Arabia, Iran and Iraq hard-hit by a drop in rainfall.

    "Resource-based conflicts are not new, but in climate change we have a new and potentially disastrous dynamic."

    Her speech echoed a similar warning from the European Commission in January that global warming could trigger regional conflicts, poverty, famine, mass migration and the spread of infectious diseases such as malaria and dengue fever.

    The British Government has this year tried to focus global attention on climate change as a security threat, and Mrs Beckett used the British chairmanship of the United Nations security council in April to convene the council's first debate on the issue.

    Meanwhile at the UN, a vote is due overnight on whether Zimbabwe will take over the chairmanship of the Commission on Sustainable Development, which oversees environmental issues in the developing world.

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