More heat waves, fewer cold waves to be the norm: Hyderabad varsity study

Hyderabad: A recent study by a University of Hyderabad (UoH) student found that in the recent decade in India heat waves have become more common in summer while cold waves have become less common in winter and that the models used by the India Meteorological Department (IMD) in the prediction of heat waves and cold waves need to be more efficient.

A study led by Aninda Bhattacharya, a student of Master of Science in Ocean and Atmospheric Sciences, used daily maximum temperature and minimum temperature data from 1970 to 2019 to come to this conclusion.

Anthropogenic, human-caused, climate change has caused roughly 1 degrees Celsius increase in global average surface temperature since the pre-industrial era, said the study.

Published in the ‘Journal of Earth System Science’, the study investigates the trend in the frequency of occurrence of days with anomalously high temperatures (commonly known as heat waves) and days with anomalously low temperature (commonly known as cold waves) over different climatic regions of India.

India has broadly four major climatic zones – montane (climate is harsher, with lower temperatures in mountainous regions), subtropical humid climate, arid and semi-arid climate, and dry and wet tropical climate.

The occurrence of anomalously higher temperatures for consecutive three days or more is referred to as a heat wave event. The occurrence of anomalously lower temperatures for consecutive three days or more is referred to as a cold wave event.

Bhattacharya found that days with anomalously higher temperatures are increasing during summer every year while the days with anomalously lower temperatures are decreasing during winter every year.

It was found that heat wave events are increasing at the rate of 0.6 events per decade and cold wave events are decreasing at the rate of 0.4 events per decade.

The study points out opposite trends in heat waves and cold waves, wherein, heat waves are more common over the arid and semi-arid climatic regions while cold waves are less so common over the same region.

It was found that the current-generation computer models, used to predict future climate with IMD, fail to capture observed spatial features in the trend in the frequency of occurrence of heat waves and cold waves over India.

The study stated that there is a need for a better process-level understanding of the factors governing these extreme events and their representations in the models over the Indian region.

This study was led by Aninda Bhattacharya, Dr Abin Thomas, and Dr Vijay Kanawade from the Centre of Earth, Ocean and Atmospheric Sciences, School of Physics at UoH, in collaboration with Prof Chandan Sarangi from IIT Madras, Dr PS Roy from World Resources Institute (WRI) and Dr Vijay Soni from IMD, Ministry of Earth Sciences, New Delhi.