This was due, he said, to the billion tonnes of sediment that the Ganges, the Brahmaputra and 200 other rivers bring from the Himalayas each year before crossing Bangladesh.
Only about a third of this sediment, he said, makes it into the Bay of Bengal.
Much of the rest is dumped in Bangladesh's vast delta, attaching itself to river banks, or even creating new islands.
Mr Sarkar said that in the next 50 years this could add up to the country gaining 1,000 square kilometres.
But others maintain that Bangladesh is going to lose land over that period.
Dr Atiq Rahman, a lead author of the UN Intergovernmental Panel on Climate Change report, told the BBC that there was little in the new research to make him think that their projection needed revising.
He said that many people living along the coast had observed that sea levels where higher now than in their grandparents' day.
"The rate at which sediment is deposited and new land is created is much slower than the rate at which climate change and sea level rises are taking place," he said.
So while some new land may be created in parts of the country, elsewhere a much larger amount of land will disappear, he said.
In any case, the new land will take decades to become useful, and so compensate for fertile farmland that was flooded.
Dr Rahman said that what is needed now is a village-by-village survey of coastal Bangladesh.
