The flood waters were rising and Sukanya Ashin realised she had to get out of her house. Her husband tried to open the back door, but it was blocked by shifting mud. So they wrapped their two-year-old in a blanket and waded through the front doorway, as their wardrobe floated off and the houses around them started to slip down the hill. They found safety. But 17 of their neighbours died in the flood.

Adapting to climate change in India will be tough. The country is poorer and hotter than the global average, and crams 1.4bn people onto a land mass slightly larger than Argentina. In the first nine months of 2024 it suffered at least one “extreme weather event”, such as a flood or a cyclone, on more than 90% of days. July to October saw the highest recorded minimum temperatures since 1901. India is the most water-stressed country in Asia, says the World Resources Institute (WRI), an NGO (see map).

Regardless of future global emissions of greenhouse gases, all these problems will get worse for years to come. Estimated spending on adaptation rose from 3.7% of GDP in 2015 to 5.6% in 2021, a huge sum that the Indian Institute for Human Settlements (IIHS), a research body, nonetheless calls “grossly inadequate”. And the obstacles to adaptation are not merely financial. India also needs political will and the spread of know-how, old and new.

For Ms Ashin, adapting has meant moving. She lives in Wayanad, a mountainous district in Kerala. A landslide, caused by heavy rain, destroyed her village and her family’s eight-acre cardamom farm in 2019. Like all her surviving neighbours, she has upped sticks and started afresh. “People who used to own their own farms are now labouring on other people’s,” she says. The World Bank predicts that climate change will force 10m-40m people in South Asia to migrate within their countries by 2050.

To avoid future tragedies, researchers in Wayanad are devising early-warning systems. Landslides are more common because extra heat causes more seawater to evaporate, making the monsoon more intense. Sometimes half a metre of rain is dumped on Wayanad’s slopes in a single day. At some point, the soil “can’t hold that much” and collapses downhill, says C.K. Vishnudas of the Hume Centre for Ecology and Wildlife Biology, another NGO. If a village is below, it can be smothered by a wall of mud and debris moving faster than the Indian speed limit. Another landslide in Wayanad in July 2024 killed hundreds.

The Hume Centre has been gathering microdata about rainfall. It has laid a grid over the map of Wayanad’s landslide-prone areas and trained farmers in every square to operate rain gauges and upload measurements to a WhatsApp group. This lets boffins at Hume estimate how water-sodden and unstable each patch of mountainside has become, so that villagers can be told when to evacuate, and where to.

Information is a tool to fight heat, too. No one knows how many people perished in the heatwaves of 2024, but 33 poll workers died in one day in one state during the country’s long election. The worst heatwaves in India will be three times as common if global warming is kept to 1.5°C, and five times if it hits 2°C, by one estimate.

The problem is most acute in cities, where the poor squeeze tightly under tin roofs. Many run micro-businesses from home, frying snacks for sale or operating machines that generate yet more heat. Slums are much hotter than richer areas, which have more shade and open space. Temperatures in October in Dharavi, a Mumbai slum that squashes 1m people into 2.4 square kilometres, are five degrees higher than in Matunga, a posher suburb next door (see map). The effect of humid heat on outdoor workers costs India the equivalent of 7% of GDP each year, estimates Luke Parsons of Duke University.

More than 100 Indian cities, districts and states have drawn up “heat action plans”, which involve planting trees, opening water kiosks in public spaces, issuing warnings and so on. Chandni Singh of IIHS and her co-authors assessed ten such plans and found them promising but inadequate. More radical change is needed, she argues, starting with heat-resilient building codes. Others call for a shift from concrete and glass to more naturally ventilated buildings with courtyards and fans.

Of all the climate-aggravated threats to Indian livelihoods, water scarcity seems the most urgent. With 18% of the world’s population, India has only 4% of the world’s fresh water, and 17 of its 28 states suffer “high” or “extremely high” water stress, according to WRI. This is likely to grow worse around population centres such as Bangalore, India’s tech capital. Almost all Indian cities rely on costly engineering to bring in fresh water from distant sources that “will completely run out” if conservation does not improve, according to a new report from the Centre for Science and Environment (CSE), a think-tank in Delhi. In March 2024 Bangalore came close to running out of water: half its 14,000 boreholes ran dry. It avoided disaster by penalising wastage, promoting recycling and paying for extra water to be trucked into poor neighbourhoods. But the problem is far from solved.

Bangalore sits on a dry plateau 600m above and 100km away from the Cauvery river, its main water source. The liquid is pumped expensively uphill through leaky pipes to supply a population of 14m (up from 5.6m in 2000). In the rainy season ill-designed drains overflow, streets flood and water is wasted. During the dry season, the city’s thirst for river water leaves the surrounding countryside parched.

By one estimate, only a third of the water Bangalore residents use is recycled. Efforts are being made to increase this. Under one scheme, urban wastewater is cleaned up—not to a level fit to drink, but enough to irrigate crops—and used to replenish depleted rural groundwater.

Naveen Kumar, a pomegranate farmer, says he previously had to drill down 200m to find water, but now has to drill only a third as deep. He is relieved. But he still worries that the water could run out one day, so he has switched to drip irrigation. If all farmers were as prudent, less water would be wasted, but incentives are skewed. Farmers pay nothing for water beyond the cost of pumping it, and even that is subsidised. So the landowners closest to canals often grow water-guzzling crops like rice and leave little for the (often lower-caste) farmers farther away.

Donors, from the World Bank to big Indian firms (which are required to give away 2% of their profits), are eager to fund water projects. Such schemes hook up more downstream farmers to irrigation ditches and persuade upstream farmers that they could make more money growing less thirsty crops, such as exotic vegetables. This requires testy negotiation, says Veena Srinivasan of Well Labs, another NGO. Farmers, in exchange for being connected to a water source, must sign contracts agreeing to plant less rice on their land. It also requires technology: Well Labs uses satellite mapping and AI to measure what works.

Urban households underpay for water, too, but companies in Bangalore are charged much more, and large buildings have to treat their own wastewater. This creates a demand for water-management services, which the city’s busy cluster of tech firms is eager to satisfy.

India is so big and decentralised that it will be hard to keep track of how well it adapts to climate change. The rich, inevitably, will cope better, since they can afford air-conditioning and homes on higher ground. But they have to breathe the same air as everyone else, so the fact that air pollution in cities like Delhi has grown unbearable could spur greener policies.

The most sophisticated cities will probably adapt most quickly. In Bangalore people tend to pay their water bills, notes Aromar Revi of IIHS; in poorer places they often don’t, making it hard to run a rational water system. Water management is improving in most Indian states, but an official survey in 2021 found that 22 out of 54 cities with more than 1m inhabitants were doing nothing at all to recycle the precious liquid. Caste prejudice does not help: some Indians recoil from using recycled water because human waste is associated with ritual pollution. Still, Sunita Narain of CSE offers a note of optimism. As climate change worsens and the need to adapt becomes obvious, innovation will speed up, she predicts. She had better be right.