More Cyclones in the Western Coast of India: An Impact of Global Warming

Global Warming is the slow increase in the average temperature of the earth's atmosphere because an increased amount of energy striking the Earth from the Sun is being trapped in the atmosphere and not radiated out into space. The naturally occurring Greenhouse gases including carbon dioxide, methane, nitrous oxide and water vapour keep ground temperature at a global average of 15 degree Celsius. Without this natural blanket, Earth's surface would be about 30 degree Celsius colder than it is today, making the planet a freezing, barren, life less place. The Greenhouse gases keep the surface warm because as the incoming solar radiation strikes the Earth, the surface gives off infrared radiation that the gases temporarily trap and keep near ground level. But now, the Greenhouse gases are present in excess in the Earth's atmosphere due to human activities and thus trapping more heat and making the atmosphere more and more warm day by day.

Since  the pre-industrial period, human activities are estimated to have increased Earth's global average temperature by about 1 degree Celsius. Most of the current warming trend is extremely likely the result of human activity since the 1950s and is proceeding at an unprecedented rate over decades to millennia.

Most of the additional heat trapped in the Earth's climate system is stored in oceans. They store more than 90% of the extra heat and act as a buffer against the effects of climate change. When the ocean gains heat, the water expands and sea level rises. The amount of expansion varies with both water temperature and pressure. For each degree, warmer water and water under great pressure expand more than cooler water and water under less pressure.

 For the last 150-200 years, it was observed that if five cyclones are developed on an average in the Arabian Sea and the Bay of Bengal combined, four cyclones might occur in the Bay of Bengal and only one in the Arabian Sea. The ideal sea temperature or SST for the formation of cyclones is 28.5 degree Celsius and the Bay of Bengal possess 28 degree Celsius SST and is considered as a warm pool region. Earlier Arabian Sea was a lot cooler than the Bay of Bengal, but now situation is changing. Cyclones draw energy from the warm pool region. Thus Bay of Bengal being in warm pool region provide a cushion for the cyclones to develop compared to Arabian Sea.

But now, the situation of Arabian Sea is changing at an alarming rate. The meteorologists have observed changes in the temperature of the Arabian Sea. The reason behind this is the additional heat supplied due to global warming. Arabian Sea is now becoming a warm pool region. According to experts, global warming is increasing the temperature of the Arabian Sea, making it more prone to cyclones. 

It is no surprise that nine of the ten hottest years since 1880 has been recorded post 2005 and more so since 2015. It is now a well known fact that  global ocean has absorbed 90% of the excess heat generated by greenhouse gas emission since 1970. This has led to anomalous ocean warming , which in turn makes cyclones intensify rapidly.

However, for the last four years, now the numeric has changed dramatically and slowly the Arabian Sea came ahead Bay of Bengal in terms of cyclonic activity with five cyclones emerging from the western side compared to three from the eastern rim. The worst factor is that all those typhoons are severe cyclones, Cyclone Mekhanu in 2018, Cyclone Vayu in 2019, Cyclone Nisarga in 2020 and recently Cyclone Tauktae in 2021.

The reason behind observing these severe cyclones in Arabian Sea is the shift to warm pool region and the rise in the sea surface temperature. The SST of Arabian Sea got raised by 1-2 degree Celsius and the cyclones gain energy from the warm water, more vapour and humid air, thus making cyclones more powerful and dangerous.

Global warming has caused many negative effects on environment. Cyclone is just one among them. We have to take necessary measures to provide a sustainable environment for our future generation. Life seems miserable if we didn't give enough importance to preserve our nature.