South Asian economies stand to lose around 1.3 percent of their collective annual GDP by 2050 even if global temperature increases are kept to 2 degrees Celsius, experts and public officials warn.
In the second half of the century, the losses are likely to increase to around 2.5 percent of GDP, warns an analysis by the Asian Development Bank (ADB).
But if temperature increases are allowed to increase above 2 degrees Celsius, losses will mount to 1.8 percent of GDP by 2050 and a staggering 8.8 percent by 2100, according to the analysis.
"South Asia is at the frontlines of climate change," said Preety Bindari, the bank's director for climate change and disaster risk management. "The numbers and the frequency of extreme weather events faced by the region are rising."
The ADB estimates that South Asia needs around $73 billion annually from now till 2100 to adapt to negative impacts of climate change if current temperature trends continue. Those would see world temperature rise by at least 3.5 to 4 degrees Celsius by the turn of the century, scientists say.
But if countries succeed in keeping temperature rise below 2.5 degrees Celsius, that cost would fall to around $40.6 billion annually, the bank said.
Public officials in South Asia say that they are aware of the risk, but adaptation measures are slow as policy-makers grapple with balancing economic growth with climate resilience.
"We know the numbers are dramatic and that we have a lot of work in our hands," Kamal Uddin Ahmed, secretary of the Bangladesh Ministry of Forest and Environment said.
But "right now the priority is to provide food for 160 million (in Bangladesh)," he said. "We have to make sure we get our climate policies right while not slowing down growth."
Moving to action
L. Chandrapala, director of Bangladesh's national meteorological department, said that while changing rain patterns and rising temperature levels were now evident, what was needed was broad policy changes that take these into account.
"We know what's happening and have a fair knowledge of why it is happening. The next step is to make sure we are prepared," he said.
That is a view shared by ADB's Bandari. "There are many priorities for these countries. In such a complex scenario it would be vital that they integrate climate considerations into their development goals," she said.
Because developing nations are loath to sacrifice growth to building climate resilience, she and other experts advocate that countries look at making their development plans climate friendly rather than trying to create climate resilience through separate efforts.
Mohamed Abdul Qayyum, secretary of the Bangladesh Department of Disaster Management, said South Asia needed an attitude shift as well.
"In South Asia we are still in the reactive mood to climate change. We need to change that to proactive," he said. Even as policy makers and governments begin making the slow shift to climate friendly development goals, financial losses are mounting.
Risks in Bangladesh
If global emissions continue on their current trend, Bangladesh is likely to face an annual economic loss from climate risks of about 2 percent by 2050, according to the bank report. That is expected to balloon to 8.8 percent by 2100.
Annual rice production could fall by 23 percent by 2080 in a country where agriculture employs half of the labor force of around 60 million.
Dhaka could see 14 percent of its territory underwater in case of a one-meter (more than 3 feet) sea level rise while South Eastern Khulna region and the delicate eco-system of the coastal Sundarbans could fare far worse, the report said.
Bangladesh's other South Asian neighbors also face mounting risks, according to ADB assessments.
Nepal could lose as much as 10 percent of GDP by 2100 due to melting glaciers and other climate extremes, while in neighboring India crop yields could decline 14.5 percent by 2050, the bank said.
India's 8,000 kilometer-long (5,000-mile) coastline also faces serious economic risk due to rising sea level, it said.
Currently 85 percent of the country's agriculture requires some level of irrigation, and that need is likely to rise with temperature increases, even as India's groundwater threatens to run short.
Sri Lanka has already seen its rice and other harvests fluctuate in recent years due to changing monsoon patterns. ADB data warns that yields in the vital tea sector could halve by 2080.
The island could also see a sharp rise in vector-borne diseases, with 350,000 people contracting such diseases by 2090 and 2,000 dying of them each year, the ADB analysis said.
Since 2007, Sri Lanka has seen a sharp rise in dengue cases, especially in the post-monsoon months. The first nine months of this year recorded 20,058 cases; last year, a peak year for dengue, saw close to 29,000 cases over the same period, according to Health Ministry data.
There is also fear that the country may be heading into a drought — the second in two years — in the last quarter of 2015.