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Alarming sign

Carbon dioxide levels in the atmosphere are at their highest in 20 million years, two British scientists have revealed.

Paul Pearson, of the University of Bristol, in the west of England, and Martin Palmer, of Imperial College, London, reported in the magazine Nature that they used the evidence of plankton shells drilled from the seabed to estimate the acidity of the seawater over a span of time-back almost to the dinosaur era. The two analysed the shells of tiny ocean creatures to build up a fossil record of the chemistry of the atmosphere for the past 60 million years.

Carbon dioxide dissolves in water to form a weak carbonic acid. They reasoned that the tissue of floating organisms would reflect the carbon dioxide levels of the world around them

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