This story was originally published by Grist and appears here as part of the Climate Desk collaboration.

A year ago, extreme heat waves in India killed dozens of people, slashed crop yields by as much as one-third in some areas, and set a landfill ablaze in Delhi, casting toxic smoke over the surrounding neighbourhoods. Temperatures soared 15 F above normal, hitting 115 F in the northern state of Uttar Pradesh and sparking more than 300 wildfires across the country. Even as power plants burned more coal to provide the power needed to keep people cool, the country experienced a nationwide electricity shortage.

Such scenes will become the norm as extreme heat, driven by climate change, kills crops, starts fires, and endangers people’s health across the globe. New research suggests India is especially at risk — and the government may be underestimating the threat.

There are roughly 1.4 billion people in India and last year, extreme heat left 90 per cent of the country vulnerable to public health risks like heatstroke, food shortages and even death, according to a recent study published by Cambridge researchers. Soaring temperatures also could slow the country’s economy and hinder its development goals, the researchers found.

Heat waves are causing “unprecedented burdens on public health, agriculture, and other socio-economic and cultural systems,” they wrote. “India is currently facing a collision of multiple cumulative climate hazards.”

But government authorities have underestimated the danger, the study found. Officials rely on a climate vulnerability assessment, designed by India’s Department of Science and Technology, that indicates a smaller percentage of the country faces high risk from climate change than the new findings suggest. Such a miscalculation could hinder India’s efforts to meet the United Nations’ sustainable development goals, like reducing hunger and poverty and achieving gender equality.

The study appeared in PLOS Climate just days after at least 13 people died from heatstroke and several dozen were hospitalized following an outdoor event in the western state of Maharashtra. A heat wave in other regions of the country forced school closures as daytime temperatures topped 104 F several days in a row.

At least 24,000 people have died from heat in India in the last 30 years. Climate change has made heat waves there and in neighbouring Pakistan up to 100 times more likely, and temperatures are expected to break records every three years — something that would happen just once every 312 years if the climate weren’t undergoing such radical changes.

“Long-term projections indicate that Indian heat waves could cross the survivability limit for a healthy human resting in the shade by 2050,” the authors of the Cambridge study wrote.

Deadly heat threatens the lives and livelihoods of one billion people in #India. #HeatWave #ClimateChange #ExtremeHeat #ClimateCrisis #GlobalHeating

With over 1.4 billion people, India is on pace to surpass China as the world’s most populous country this year. As the nation’s heat-caused death count rises, its economy will slow, the researchers project. By 2030, intense heat will cut the capacity for outdoor work by 15 per cent — in a country where, by one estimate, “heat-exposed work” employs 75 per cent of the labour force. Heat waves could cost India 8.7 per cent of its GDP by the end of the century, the Cambridge researchers wrote.

Yet the government’s climate-vulnerability assessment doesn’t account for more intense and longer-lasting heat waves, according to the study. The Cambridge researchers found that all of Delhi — home to 32 million people — is endangered by severe heat waves, but the government says just two of the city’s 11 districts face high climate risk. Overcrowding, lack of access to electricity, water, sanitation, and health care, along with poor housing conditions, could leave Delhi’s residents — particularly those who are low-income — even more vulnerable to heat, the study’s authors wrote, noting a need for “structural interventions.”

The government “hasn’t understood the importance of heat and how heat can kill,” Dileep Mavalankar, director of the Gujarat-based Indian Institute of Public Health, told BBC.

Meanwhile, India’s power ministry has asked coal-fired power plants to ramp up production to meet electricity demand, which hit a record high as temperatures eclipsed 110 F.