Omens of deluge

Estimates of sea-level rises vary considerably

Published: Sunday 31 July 1994

SCIENTISTS associated with the Intergovernmental Panel on Climate Change have predicted that by the year 2050, the sea level is likely to rise by 0.3-0.5 m. This is assuming that no effort is made to check greenhouse gas emissions, which heat up the atmosphere and cause the polar ice caps to melt. Using sophisticated computer modelling techniques, they calculated that by 2100, a 1-metre rise in sea level is likely.

But determining changes in the level of the sea is no easy task. For instance, scientists of the Ocean Engineering Centre at the Indian Institute of Technology in Madras calculated on the basis of historical data that the average sea level rise on the eastern Indian coast is 0.67 mm per year.

However, an analysis of similar data by another group of scientists reveals that the sea level at 5 stations spread along both the eastern and western Indian coasts has risen by an average 2.8 mm per year. One of the scientists associated with the later study cautions that "there is still a considerable uncertainty about the rise in sea level due to global warming in the Indian region".

Explains Virendra Asthana of Jawaharlal Nehru University's school of environmental sciences, "The analysis of tide gauge data is extremely difficult due to background noise caused by the natural rise or subsidence of land." This, he says, clouds data and makes it difficult to separate land movements from actual rises in the sea level.

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