On a stiflingly hot morning, Daw Mya Htay rolls up her longyi, a Burmese sarong, ready to wade into the sea.

“The well used to be the centre of our village,” Mya Htay says, grasping the side of a cement water well. But it no longer holds fresh water.

For the people of Khindan, the well is symbolic of their losing battle with the sea.

Ten years ago, the town noticed erosion of the beachfront. Five years later, the well was swallowed by the sea.

“Because of the storm surges, my old house was destroyed. The sand deposits just fell away,” says Mya Htay. Two kilometres of the village coast have been affected by accelerated erosion.

Of 183 countries, Myanmar is the second most vulnerable to extreme weather events. Photograph: Libby Hogan/The Guardian

Two weeks ago, the UN jolted the world with the message that we have 12 years to limit climate catastrophe. Its report urged action to cut carbon emissions to avoid the atmosphere warming by a disastrous 3C. In countries such as Myanmar, even a modest rise could be the tipping point for a new conflict over water and a new wave of climate refugees.

Worldwide, Myanmar is the second most vulnerable country to extreme weather events. The effects are widespread: in the dry zone, home to nearly a third of Myanmar’s total population, temperatures are projected to rise by up to 3C after 2040. In the Irrawaddy delta, in the south – where people are still rebuilding after the country’s worst natural disaster, Cyclone Nargis, which displaced 2.4 million people – the mid-level projection for sea-level rise is up to 40cm by 2050.

A sea level rise of roughly 13cm by 2020 may sound less alarming than the rate in the Republic of Kiribati, a group of Pacific islands that at risk of being totally erased this century. But climate consultant Sonia Leonard, who is working in Mon state with environmental organisation Alarm, points out that in low-lying floodplains where more than 140,000 people live, this increase will result in permanently flooded areas and a loss of productive agriculture land.

People in Khindan have had to migrate from their homes several times. They have moved back as far as they can go on vacant land. “Now they’re literally just waiting for their houses to fall into the sea,” says Leonard, who is mapping vulnerable communities likely to be displaced by climate change.

This year more than 150,000 people across Myanmar were displaced by flooding. What was once consistent rainfall has been replaced by a more intense monsoon, causing flash-flooding.

“We feel like hermit crabs, we do not have a place to live,” says Khin Ohn Myint, her voice wavering as she looks at the bones of her house in the sea.

What’s most striking is that this year has been par for the course in terms of abnormal monsoon periods and natural disasters.

“If this is just a normal year, with a large storm surge that has been slowly intensifying each year, what happens when a big cyclone hits again?” asks Leonard.

In Khindan, the population visible on the streets consists mostly of elderly people and young children. Village elder Aung Shein’s situation is typical: “My children have had to go across the border [into Thailand] to look for work, so we are looking after their children,” he says.

As people lose their land, experience a drop in crop productivity and struggle with declining water availability, many in Myanmar’s rural or coastal areas are migrating to the cities. Outmigration is also high, with more than 4 million Myanmar migrants working in Thailand alone.

Lack of fresh water in Myanmar has already forced many people to leave their homes. Photograph: Libby Hogan/The Guardian

The new government has started to provide financial aid of 20,000 kyat (£9.65) for each household affected by natural disasters, but even officials concede this isn’t much for people who lose their houses or land.

Shashank Mishra of the Myanmar Climate Change Alliance believes access to water could spark conflict in the future. He points to the dry zone, where people have already been forced to leave their homes due to lack of water or an increase in temperature. “The total monsoon period has already decreased from 144 days per year in 1998 to 125 days,” Mishra explains.

The number of extremely hot days is projected to increase from one day a month to between four and 17 by 2041, adds Mishra, which will also cause serious health problems.

Ten years after Cyclone Nargis, some villages have received new cement tanks to hold fresh water, but there remains a pressing need for better adaptation planning.

Leaning over a map of the Irrawaddy delta, field officer Win Naing explains: “We have built two storm shelters here in these central villages, and we are trying to build more mangroves to shelter village coastlines.”

But if another intense cyclone hits – and since the 80s, cyclones in the Bay of Bengal have increased in number, often developing into hurricane-force storms – taking shelter in a multipurpose shelter may not be enough.

One expert who has worked in Bangladesh advocates a “land bank”, for the government to earmark vacant land that can be allocated to future climate-displaced people. Setting aside parcels of land, which vulnerable communities can move, to is a concrete solution in a rights-based approach that aims to prevent land conflict.

Scott Leckie of Displacement Solutions in Australia warns: “In most places in the developing world they [climate migrants] will end up landless, migrating from rural areas and ending up in slums in the cities with severe increased poverty, if there is no assistance.”

U Hla Maung Thein, from the environment and conservation ministry, says the government is trying to work towards the goals set in the Paris agreement. “We have initiated plans such as a fish adaptation project, and for a community forest in Hinthada in the Ayeyarwady division and Chauk in the Magway region.”

Climate activists welcome the government’s pledges, but say implementation must be quicker.

Back in Khindan, Daw Mya Htay gives her grandson a push on his bike while discussing climate change. She sighs. “It would be convenient if there was no sea level rise,” she says. Then, turning back to her house she shrugs. “But if it does, where will we go?”