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doi:10.1038/nindia.2017.80 Published online 11 July 2017

Human activities may trigger rapid warming in India

Madhukara Putty

Uncontrolled human activities could make India warmer by 5°C by the end of 21st century as compared to the relative average temperature between the years 1901 and 1960,  according to a new study1. Also,  it would not just be hot days but also cold events would become more common across the country between 2080 and 2099, the study says.

Collating India’s temperature data over 145 years, researchers have found that between 1860 and 1905, the surface temperature over India increased on an average by 0.055°C each decade. Between 1969 and 2005, India warmed at a much faster rate of about 0.2°C per decade.

But warming has not been uniform over the entire country. Central India experienced severe warming while the northeastern and Himalayan regions have cooled down a bit.

Ghouse Basha, lead author of the study from Tirupati-based National Atmospheric Research Laboratory, along with colleagues from the USA and Canada, simulated India’s future climate by using state-of-the-art climate models. Simulations showed that under strict climate interventions, warming over India would peak in 2050 and enter a cooling phase afterwards. In the absence of climate action, land surface temperature could increase by upto 5°C and make extreme climate events much more frequent by the end of 21st century. They computed temperature increases relative to the 1901-1960 average.

Basha says a variety of factors, both natural and human-induced, influence long-term climate. The rapid warming observed in India, however, is primarily due to human activities. “Changes in land use and land cover, and a substantial increase in greenhouse gas emissions are the major factors for warming over India,” he says. Warming can be reduced by controlling anthropogenic aerosols and land use changes at the regional levels.

Interestingly, however, the study revealed that anthropogenic aerosols have slightly reduced the rate of warming.

Subimal Ghosh, Associate Professor at the Indian Institute of Technology-Bombay, Mumbai, thinks that the study could help understand warming over India better by analysing land surface temperature data and by incorporating the impact of land use changes in the projections.

Ghosh says felling of forests for agriculture and rapid urban growth have been the main drivers of changes in land use and land cover in India. “Vegetation loss lowers evapotranspiration which leads to higher land surface temperature”, he says. Ghosh’s earlier studies have shown that these factors weaken the Indian monsoon and contribute to warming2, 3.


References

1. Basha, G. et al. Historical and projected surface temperature over India during the 20th and 21st century. Sci. Rep. 7, 2987 (2017)

2. Paul, S. et al. Weakening of Indian summer monsoon rainfall due to changes in land use land cover. Sci. Rep. 6, 32177 (2016)

3. Shastri, H. et al. Flip flop of day-night and summer-winter surface urban heat island intensity in India. Sci. Rep. 7, 40178 (2017)