No winter in Bangladesh by 2100?

Bangladesh's average temperature could rise sharply in the coming decades -- potentially by up to 4.5°C by 2100 -- if greenhouse gas emissions are not reduced, a new study has warned.

The study warns that winter could vanish entirely by the century's end, with nearly 18% of the nation's coastal land at risk of going underwater.

Rising sea levels and intensified flooding could also displace around 900,000 people across Bangladesh by 2050, the study also said.

The findings were presented in a new research report titled "Bangladesh's Future Climate", which was released on Wednesday at a Dhaka hotel.

The report was jointly prepared by the Bangladesh Meteorological Department and the Norwegian Meteorological Institute, with technical support from Save the Children. It was led by meteorologist Md Bazlur Rashid.

Speaking to The Daily Star, Bazlur Rashid said the study report provides forecasts for five types of climate scenarios. It divides the remaining part of the century into two periods: 2041–2070 and 2071–2100.

Norwegian climatologist Hans Olav Hygen delivered the keynote presentation.

Hygen told The Daily Star that the positive side of the report is that Bangladesh can take preventive measures before these threats become unmanageable.

The report also says Bangladesh is likely to experience far more intense and frequent heatwaves. Western districts, in particular, may face extreme heat almost throughout the year. By the 2070s, pre-monsoon heatwaves in western regions could last up to 20 days, and by the century's end, nearly 70 of the 90 pre-monsoon days may experience heatwave conditions.

Dhaka, too, is projected to encounter at least two severe heatwaves every year -- one before and one after the monsoon, the report read.

The study warns that Bangladesh's winter season may nearly disappear within decades. In the country's northeast, mild cold spells may occur for only a day or two during December–January, while winter characteristics across southern districts may vanish entirely.

Monsoon precipitation could increase by an average of 118mm by 2070 and by 15 percent -- or around 255mm -- by the end of the century.

The report estimates that coastal waters around Bangladesh may rise 3.8 to 5.8 millimetres annually -- more than double the global average of 2.1mm. As a result, 12–18 percent of coastal lands may be permanently submerged by 2100.

The Sundarbans could lose up to 918 square kilometres -- about 23 percent of its area -- to rising waters.