Classes on board the Nauka school. Photo: Jaspreet Kindra/IRINThe monsoon season has not quite drawn to an end and just to prove it, the heavens open in an intense 15-minute downpour. The rain elicits more giggles from the children, who scamper for refuge under the trees lining the bank. Then a solar-powered boat with a sign "Nauka [Boat] School" suddenly appears on the horizon and slows down as it draws nearer to pull up beside the bank.The dripping children queue to get to their classes on board - a rainy day is not an excuse to play hooky in this part of the world. "Nauka schooley jaye khoob moja hoye [When we attend the boat school, we enjoy ourselves]," a giggling Shakila Khatoon, 9, said in Bengali, or Bangla, the national language."It's different from other schools – I really love the Bangla boi [book] – it teaches us things we see in our villages, helps us identify the birds, kinds of fishes, and tells us about river erosion."Women and older villagers watch the bobbing fishing boats from the bank while they wait patiently to catch the "health boat", the "library boat" or even the "agricultural extension boat", all due to arrive sometime that day.In a few weeks, some of the landless families in the region might even settle permanently on houseboats lashed together to form small floating villages, with a community boat in between.Architect-turned-activist Mohammed Rezwan is determined to prove that Bangladeshis can survive the climate change scenario, in which land steadily vanishes beneath relentlessly rising water, by staying afloat. "This is the future - various climate change forecast models have predicted that one-fifth of Bangladesh could be under water by 2050," he said.The impact of global warming will hit Bangladesh hard. Soaring global temperatures are increasing glacial melt in the Himalayan ranges, swelling the rivers that flow down from the mountains and across the Bangladeshi floodplain, the largest in the world, far beyond their capacity.The expanding volume of water is also causing higher sea levels to push inland. A rise above one metre, which could be reached in this century, means Bangladesh could lose 15 percent to 18 percent of its land area, turning 30 million people into "environmental refugees" by 2050, according to some estimates, says the United Nations Development Programme (UNDP).Extreme weather events such as cyclones are also expected to become more frequent and intense as a result of global warming.Couldn't go to schoolRezwan grew up in the nearby village of Shidhulai and was often unable to go to school during monsoons, when the roads were flooded. "Schools would be closed for months," he commented. In 2007 more than 4,000 primary schools were closed, at least another 4,000 were affected and 44 were washed by river erosion, the UN Children's Fund (UNICEF) reported.