The frequency of heat waves and their duration in India may begin to increase from as early as 2020, says a study by the Indian Institute of Tropical Meteorology (IITM), even as the large swathes of the country are currently sweltering in heat waves with temperatures exceeding 45°C.
The study says that the “El Nino Modoki”, a weather system different from El Nino, could be responsible for the increase in heat waves in India. Depletion of soil moisture and transfer of heat from the earth to the atmosphere would also trigger them, reported Times of India quoting the report.
These events are likely to happen between 2020 and 2064, affecting parts of southern India and coastal regions that have till now largely escaped heat waves.
The study, called “Future Projections of Heat Waves Over India from CMIP5 Models” and published in the international journal Climate Dynamics, examined nine climate models to understand how the frequency, intensity and duration of heat waves in India will increase and its severe and adverse impact on health.
The models used in the study identified 54 heat-wave events in India between 1961 and 2005. This number is likely to go up with the probability of 138 heat-wave events between 2020 and 2064.
The findings suggest that frequency, duration and spatial extent of heat waves over India are found to be more in the succeeding year of El Nino where the eastern Pacific Ocean warms up and is warmer than the central and western Pacific Ocean. In an El Nino Modoki event, the central part of the Pacific ocean warms more with cooling in the eastern and western parts. A stronger relationship is emerging from the central and western parts of the equatorial Pacific. El Nino Modoki events may be responsible for the prolonged and more frequent heat waves in India.
“Future projections suggest an increase in heat wave frequency and duration across the country from 2020. The models used for the study suggested an increase of 1.5-2.5 heat wave events, with an increase of 12-18 days on an average between 2020 and 2064. This is a noticeable increase but is subject to model projection uncertainties in both the heat-wave events and heat-wave days,” Dr P Mukhopadhyay, a scientist at IITM who conducted the study, told Times of India.
Atmospheric conditions during heat-wave events over northwest India are associated with depleted soil moisture, he added.