NEW DELHI: Sea levels along the Indian coast have risen by 8.5 cm during the past 50 years with an average increase of 1.7 mm per year, said the government in Rajya Sabha as it shared data from 10 major ports across the country in response to a Parliament question.

Compared to global data, the annual average seal level rise along Indian coast is, however, almost half at present. UN’s latest Intergovernmental Panel on Climate Change (IPCC) report shows that the sea level globally is currently rising at the rate of 3.6 mm per year and “accelerating”.

The long-term data, collected at 10 Indian ports, indicates sea levels at Diamond Harbour in

recorded the highest annual average increase (5.16 mm/year) followed by Kandla (3.18m/year) in Gujarat, Haldia (2.89 mm/year) in West Bengal, Port Blair (2.2 mm/year) in Andaman & Nicobar Islands and Okha (1.5 mm/year) in Gujarat.

These annual average figures were, however, not taken during the same period or for the same duration at all ports. Even though the data may not be exactly comparable, but experts say they give a fair idea of

as figures were recorded over a longer period ranging from 28 years in the case of Okha to 128 years for Mumbai.

The government in its response in Rajya Sabha, however, said that the rate of increase of sea level cannot be attributed to climate change “with certainty” as no long term data on land subsidence or emergence are available for these locations.

Citing examples, the minister of state for environment,

, in his written response told the Upper House on Monday that the highest rise of sea level increase at Diamond Harbour was also due to the large-scale land subsidence seen happening there. The same may apply to Kandla, Haldia and Port Blair as well, he added.

Speaking about its impact, the minister said, “The rising sea levels can exacerbate coastal inundation along low lying areas during the extreme events such as tsunami, storm surge, coastal flooding and coastal erosion.”

He suggested coastal areas that might get inundated due to the rising sea level need to be evaluated based on their elevation above mean sea level.

The figures, cited by the minister, was taken from the ministry of earth sciences (MoES) which has been working on India-specific report on impact of climate change, collecting all measurable data from different scientific institutions. Its data from satellite altimetry and model simulations shows that the North Indian Ocean (NIO) exhibits decadal variability, experiencing much higher sea level rise at a rate of 6.1 mm/year during 2003-13.