Alarming sign

Carbon dioxide levels in the atmosphere are at their peak, claim UK scientists

 
Published: Friday 15 September 2000

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 -- and then hold that record locked in the fossilised shells. Other studies of more recent records have confirmed a picture of a rapid warming in the past two decades: winter is in retreat, seasons in Europe are 11 days longer than it was 35 years ago and sea levels have crept higher throughout the century.

Six of the 10 warmest years ever recorded occurred in the 1990s; the other four all happened in the 1980s. The Arctic ice cover is in retreat, shrinking by an area the size of the Netherlands every year. It is also thinning -- from more than three metres thick to less than two metres in 30 years.

Their discovery should pressure governments to implement international agreements to reduce the greenhouse gases that fuel global warming. The news comes after a report released by the University of Colorado that shows that Arctic temperatures are at their warmest in at least 400 years.

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