Some academics have challenged a recent study that said that “temperature during India’s main agricultural-growing season has a strong positive effect on annual suicide rates”.
The paper, titled “Climate change and agricultural suicides in India” and authored by Tamma A. Carleton, has been published in the PNAS journal (Proceedings of the National Academy Sciences of the United States).
The study had used State-level data from 1967 to 2013 to suggest that an increase in temperature by a degree Celsius a day can cause 70 suicides.
The evidence, it said, leads to the conclusion that crop damage by extreme temperatures leads to economic hardship and suicide.
In a press note, T. Jayaraman and Kamal Kumar Murari of the Tata Institute of Social Sciences and Madhura Swaminathan of Indian Statistical Institute said they considered these claims to be baseless. “These claims are a consequence of the uncritical use of data, bad assumptions, flawed analysis and unacceptable neglect of the existing literature on global warming and Indian agriculture as well as farmer suicides,” they said.
The academics noted that the author incorrectly used suicide data, wrongly identified extreme temperatures for crop production, took only kharif as the relevant agricultural season to consider extreme temperatures, and wrongly identified the relevant crops.
As a result, the meaning of the correlation that the author claimed to find between extreme temperatures and suicides was unclear.
They said the paper used State-level data on suicides, both urban and rural. “How can urban suicides be included in an analysis of agricultural suicides,” they asked.
The paper ignored the fact that the suicide data, taken from the National Crime Records Bureau, had separated farmer suicides from those of other occupational categories only after 1995.
The author did not analyse individual crops but only considered a few such as rice, wheat, sorghum, sugar, maize and millet.
Cotton, closely associated with farmer suicides, was a notable omission as are a host of other cash crops. The author also ignored the Rabi season.
The paper considered temperatures above 20 degrees Celsius as extreme temperatures.
This was flatly contradicted by what was known of the temperature dependence of crop production, the academics noted.