Climate change has caused more than 59,000 farmer suicides in India over the last 30 years, a study has found, warning that suicide rate across the country will increase substantially as global temperatures rise.
The findings by researchers at University of California, Berkeley in the US suggest failing harvests that push farmers into poverty are likely the key culprits.
Researchers found that temperature increase of just one degree for a day during the agricultural growing season leads to roughly 65 suicides across the country, whenever that day's temperature is above 20 degrees Celsius.
Temperature rise of five degrees Celsius a day has five times that effect, researchers said.
"It was both shocking and heartbreaking to see that thousands of people face such bleak conditions that they are driven to harm themselves," said Tamma Carleton, researcher at UC Berkeley.
"But learning that the desperation is economic means that we can do something about this. The right policies could save thousands," said Carleton.
While high temperatures and low rainfall during the growing season substantially impact annual suicide rates, similar events have no effect on suicide rates during the off-season, when few crops are grown, implicating agriculture as the critical link.
The study, published in the journal Proceedings of the National Academy of Sciences, helps explain India's evolving suicide epidemic, where suicide rates have nearly doubled since 1980 and claim more than 130,000 lives each year.
The results indicate that seven per cent of this upward trend can be attributed to warming that has been linked to human activity, they said.
More than 75 per cent of the world's suicides are believed to occur in developing countries, with one-fifth of those in India alone, researchers said.
However, there has been little hard evidence to help explain why poor populations are so at risk.
The study demonstrates that warming - forecast to reach three degrees Celsius by 2050 - is already taking a toll on Indian society.
Researchers projected that the suicide rate will only rise as temperatures continue to warm.
Debate about solutions to the country's high and rising suicide rate is contentious and has centred around lowering economic risks for farmers.
In response, the Indian government established a USD 1.3 billion crop insurance plan aimed at reducing the suicide rate but it is unknown if that will be sufficient or effective, researchers said.
More than half of India's working population is employed in rain-dependent agriculture, long known to be sensitive to climate fluctuations such as unpredictable monsoon rains, scorching heat waves, and drought. A third of India's workers already earn below the international poverty line.
Carleton tested the links between climate change, crop yields and suicide by pairing the numbers for India's reported suicides in each of its 32 states between 1967 and 2013, using data from the Indian National Crime Records Bureau, along with statistics on India's crop yields, and high-resolution climate data.
To isolate the types of climate shocks that damage crops, Carleton focused on temperature and rainfall during June through September, a critical period for crop productivity that is based on the average arrival and departure dates of India's summer monsoon.