Mumbai, Kolkata, Chennai may go under water by 2100

Days before the Copenhagen conference on climate change kicks off, a major study by a group of 100 international scientists has said that sea levels are likely to rise by as much as 1.4 metres (more than 4 feet) by the end of this century. That’s twice as much as previously predicted in IPCC’s fourth assessment report of 2007. The report released by the Scientific Committee on Antarctic Research (SCAR) is the first comprehensive review of the impact of global warming on Antarctica. The IPCC’s 2007 report had projected that sea-levels could rise by 18cm to 59cm by 2099. Subsequent studies in Greenland and Antarctica had raised fears that sea rise could be much higher. The currant study says loss of ice from west Antarctica alone could add tens of centimetres to sea level ‘‘We can see the west Antarctic glaciers are shrinking at a rate fast enough to contribute to a sea level rise of 1.4 m by 2100, but it will be no more than that,’’ SCAR executive director Colin Summerhayes said in London. If these projections come true, most low-lying island nations like the Maldives would go under the sea. The UN’s environmental panel had earlier warned that sea levels would be high enough to make the Maldives uninhabitable by 2100. The new study also significantly enhances the threat to the Indian coast — and cities like Mumbai, Chennai and Kolkata. ‘‘Anybody who lives in coastal cities needs to be slightly worried by projections of 1 metre or more,’’ Summerhayes said. ‘Over 90% of glaciers across Antarctica have retreated’ Since 1870, global sea level has risen by about 20cm at an average rate of 1.7 mm/year. But in recent decades, the rate has risen sharply to 2.5mm/year, according to the latest figuress. The rise in sea level is mainly a result of thermal expansion of the ocean due to global warming as well as increased water inflows from melting glaciers and ice caps. Reports by the Scientific Committee on Antarctic Research and studies by UN’s environmental panel says that central Antarctica, that has so far been protected from warming due to a hole in the ozone layer, will also see the full effects of greenhouse gas increases as the ozone hole heals. The scientists found that there has been significant thinning of the west Antarctic ice sheet and 90% of glaciers across the Antarctic peninsula had retreated over recent decades. But the bulk of the Antarctic ice sheet has shown little change over recent decades.