Coastal cities like Visakhapatnam, Mumbai, Kochi and Chennai are facing long-term threats from the sea as the average sea levels in these cities are going up by 1.30 mm every year.
Data collected by Hyderabad-based Indian National Centre for Ocean Information Services showed that the trend of mean sea level rise varied from 1.06 mm to 1.75 mm per year on the Indian Ocean, including the Arabian Sea and the Bay of Bengal.
Analysis of 113 years of data of Mumbai revealed that the increase in the mean sea level was 1.20 mm per year while 54 years of data of Kochi showed an average increase by 1.75 mm per year.
In Visakhapatnam, the data for 53 years showed a net sea level rise of 1.09 mm per year. Diamond Harbour (Kolkata), which has data for 55 years, shows an average increase in sea level by 5.74 mm, the highest for any sea-side city in the Indian Ocean.
The rise has been attributed to an increase in the temperatures of the sea. The annual mean sea surface temperature has risen by 0.31°C, 0.40°C and 0.24°C per decade in Mumbai, Kochi and Visakhapatnam respectively.