‘Climate change fuelling Chennai’s extreme weather’

The extreme weather conditions being witnessed in the State — be it the rising maximum temperatures, cyclonic disturbances, or extreme rainfall — are a result of climate change, say experts.

In the case of the metropolis itself, since the catastrophic Chennai floods in December 2015, the city has had several other extreme weather conditions. A few months ago, in November 2021, the whole city of Chennai was waterlogged with heavy rains, which even claimed 14 lives. Flagging the human fingerprint, environmentalists and weather experts point to the loss of green cover, pollution, and poor maintenance of water bodies as major reasons that have contributed to climate change.

Rising maximum temperature

As per the data with the Indian Meteorological Department (IMD), 2021 was the fifth warmest year since 1901, since the nationwide recording commenced. With the onset of summer, Chennai recorded the highest maximum temperature of 38 degrees Celsius on March 22. The highest recorded temperature of 38.3 degrees Celsius was reported on March 31, 2021.

The rise in maximum temperature in March marked an early onset this year. Environmentalists say that climate change seems to play a major role in increased maximum temperatures over years. The highest maximum temperature in the past in March is about 40.6 degrees Celsius in 1953. The maximum temperature in March remained around 35-36 degrees Celsius for the past ten years and it remained 34.4 degrees Celsius in 2020.

“Climate change has led to warming of the Earth, which leads to certain weather conditions such as the shift of moisture, rise in temperature, unpredicted rainfall, and other climatic variations. The onset of summer saw about 38 degrees Celsius a few days ago and now it has dropped to 34 degrees Celsius. Such variations in the temperature are a result of climate change,” said S Balachandran, Deputy Director-General of Meteorology, Regional Meteorological Centre, Chennai.

Excess rainfall, frequent depression

The rainfall is having high temporal and spatial variability due to the impact of climate changes. There are significant changes in the mean rainfall pattern and their variability as well as in the intensity and frequencies of extreme rainfall events in the State.

“The annual rainfall received in 2021 was about 105 per cent of its long period average for a period of 50 years between 1961-2010. Indian Meteorological Department recorded Tamil Nadu as one of the States that saw extremely wet-severely wet conditions in 2021. There is an increase in the frequency of extremely severe cyclonic disturbances over Arabian sea and cyclonic formations in the Indian Ocean,” says Mrutyunjay Mohapatra, Director General of Meteorology, IMD.

As many as 759 deaths were recorded in the country due to floods, landslides or heavy rains in 2021 and 787 deaths due to lightning and thunderstorm of which Tamil Nadu witnessed close to 40 deaths, mainly due to floods or thunderstorms. About 12 districts have been impacted due to the same in the State. He added that the heatwave condition has increased in several districts showing a significant increase in temperature from 1961 to 2021.

Weather blogger Pradeep John stated that the State witnessed more low pressure in 2021, where the Bay of Bengal was active during the northeast monsoon, so we received intense rainfall. However, there was not much rainfall in 2019, as at least four to five cyclones formed in the Arabian Sea. Earlier, the State has also recorded drought situations in 2003, 2016, and 2017, where it received very moderate rainfall. From 2004-to 2011, the State received consistent rainfall, because it is not normal to receive rainfall continuously for seven years. But for the next three years, there was moderate rain but did not have enough rain for the inflow. In 2016, the monsoon failed, as 50 per cent of rainfall is dependent on seasonal rainfall.

In a rare instance, depressions were formed near Tamil Nadu in March this year. In 1938, such depression was near Sri Lanka and in 1994, the depression was near Andaman and Nicobar Island.

Effect on migratory birds and animals

“The climate change causing drought or excess rainfall leads to a change in the pattern of migratory birds. In 2021 November, the migratory birds expected at Pallikarnai marshland moved to other states due to excess rainfall in the city. The birds had arrived in 2020 but excess rainfall resulted in a diversion,” says KVRK Thirunaranan, a bird tracker and founder of the Nature Trust.

“The season for most of the migratory birds is from October to March but it is seeing a change in the pattern due to several effects of climate change. Over the years, the flora and fauna can be impacted due to climate change,” he added.