Sea levels are rising unevenly in the Indian Ocean, placing millions at risk along low-lying coastlines in Bangladesh, Indonesia and Sri Lanka, scientists say in a study.

Researchers from the University of Colorado and the National Centre for Atmospheric Research say the rising sea levels are caused in part by climate change and are triggered by warming seas and changes to atmospheric circulation patterns.

In his acceptance speech for the Nobel Peace Prize last year, US President Barack Obama warned that if the world does nothing to confront climate change, \”we will face more drought, famine and mass displacement that will fuel more conflict for decades\”.

The authors of the latest study say higher seas could exacerbate monsoon flooding, placing crops, homes and livelihoods at greater risk. They argue a better understanding of the changes are needed to improve risk assessment planning for the future.

Sea levels in general are rising globally by about 3mm a year. Scientists blame rising temperatures caused by the growing amounts of greenhouse gases, such as carbon dioxide from burning fossil fuels, that trap heat in the atmosphere.

Oceans are absorbing a large part of this extra heat, causing them to expand and sea levels to rise. Warmer temperatures are also causing glaciers and parts of the ice blanketing Greenland and West Antarctica to melt.

The team of researchers in their study used long-term tide gauge data, satellite observations and computer climate models to build a picture of sea level rises in the Indian Ocean since the 1960s.

They found that sea-level rise is particularly high along the coastlines of the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra and Java and that these areas could suffer rises greater than the global average.

But they also found that sea levels are falling in other areas. The study indicated that the Seychelles Islands and Zanzibar off Tanzania\’s coast show the largest sea-level drop.