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Predictions of the globe's food supplies based on inadequate informati on

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    ... CO2 not certain to counter climate change By Clive Cookson, Science Editor Published: September 6 2005 03:00 | Last updated: September 6 2005 03:00 The
    Message 1 of 1 , Sep 6, 2005
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      CO2 not certain to counter climate change
      By Clive Cookson, Science Editor
      Published: September 6 2005 03:00 | Last updated: September 6 2005

      The world cannot count on the "fertilising" effects of carbon dioxide
      to counteract the adverse impact of global warming on crop yields,
      according to a paper presented to the British Association Science

      To make matters worse, crop yields are very vulnerable to the
      increasing low-level ozone pollution expect-ed to accompany climate

      Scientists have simulated in open fields the effects of the
      atmospheric changes expected to take place over the next 50 years -
      and discovered the benefits predicted from greenhouse experiments do
      not materialise. Steve Long, a crop scientist at the University of
      Illinois, told the festival in Dublin: "Current projections of global
      food supply under climatic and atmospheric change are likely to be
      very optimistic."

      Maize, the world's most extensively grown grain, did not benefit at
      all when carbon dioxide was pumped into large open fields in
      Illinois, using computer-controlled discharge rings that maintain
      steady high levels of CO2 whatever the wind direction. Other
      important crops such as wheat and soya beans showed just half the
      fertilising effect of increasing CO2 that research in closed
      greenhouses had suggested.

      In addition, Prof Long said, an experiment with soya beans, the most
      important leguminous crop, would yield 20 per cent less by 2050, as a
      result of increasing ozone, a pollutant related to photochemical smog.

      Martin Parry of the UK Meteorological Office's Hadley Centre said
      research sponsored by the government suggested climate change over
      the next 50 years would by itself add 50m to the 500m in the world
      who do not have enough to eat. Three-quarters of these would be in

      Prof Parry said current calculations of the impact of global warming
      on agriculture assumed a significant boost to crop yields from
      atmospheric changes, to counteract partially the adverse climatic
      impacts of higher temperatures and lower rainfall. But the Free-Air
      Concentration Enrichment (Face) experiments described by Prof Long
      threw that into doubt.

      "We were imagining a 10 to 20 per cent positive effect from
      additional CO2 for the UK," Prof Parry said. "We were expecting to
      see yield reductions [as a result of global warming] of 2.5 to 5 per
      cent in Africa - without the CO2 effect, that could be a 5 to 10 per
      cent reduction."

      The Face experiments take place in large round plots within huge open
      fields. Each ring is bristling with sensors that detect gas
      concentrations and wind direction inside the crop, so gases can be
      discharged at the right points to simulate atmospheric pollution.

      "Evidence for crops' response to CO2 and ozone are based largely on
      studies within chambers and glasshouses at small scales," said Prof
      Long. "Such facilities would be considered unacceptable for standard
      agricultural trials of agrochemicals or new crop varieties. Yet the
      world community is basing its predictions of the globe's food
      supplies on such inadequate information."


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