Methane good news
An independent academic study has found India's emissions of methane, a major greenhouse gas that drives global warming, are consistent with the government's estimates and have shown little growth over the past five years.
- Published 16.10.17
New Delhi: An independent academic study has found India's emissions of methane, a major greenhouse gas that drives global warming, are consistent with the government's estimates and have shown little growth over the past five years.
The study has found that India's average emissions of methane emissions - mainly from paddy fields and cows, among other sources - were about 22 trillion grams per year between 2010 and 2015, consistent with India's emissions reported to the United Nations Framework Convention on Climate Change.
The scientists who conducted the study say their estimates for India's methane emissions are about 30 per cent smaller than figures in a global inventory of greenhouse gases calculated by an international research consortium called the Emissions Database for Global Atmospheric Research.
"Our approach should help bolster confidence in India's official estimates," said Anita Ganesan, an environmental chemist at the University of Bristol in the UK who led the study published on Tuesday in the journal Nature Communications. "Estimating the methane emissions is particularly challenging, and this work demonstrates a new way to do that."
The concentrations of methane, the second-most powerful greenhouse gas after carbon dioxide, have been growing in the atmosphere in recent years. But methane emissions are much harder to estimate because they emerge from biological systems influenced by the environment.
"Methane emissions from rice paddies, for example, are influenced by temperature, rainfall or irrigation, fertiliser applications, so emissions can vary dramatically from one place to another and at different times," Ganesan said. "This makes methane more difficult to account for in inventories."
Ganesan and her colleagues from institutions in Germany, India, the UK and the US combined satellite imagery and ground and aircraft observations with computer models of the atmosphere and winds to arrive at estimates for methane emissions for each month between 2010 and 2015.
Their study showed spikes in methane between June and September each year, the monsoon season, when paddy is grown across the country. The stable methane emissions in India contrast with China where measurements have suggested increasing emissions of methane in recent years.
Ganesan said the growth in China has been shown to be driven by large increases in fossil fuel emissions of methane. In India, fossil fuels make up a much smaller source of the methane emissions, which are overwhelmingly generated from agriculture - paddy and livestock.
The study also showed a small winter peak in emissions, which the scientists say could be due to winter rice that makes up about 14 per cent of total rice production in India or due to increases in fossil fuel emissions.