Frequent cyclones linked to climate crisis
NEW DELHI: The severe cyclonic storm which made landfall south of Alibag in Maharashtra’s Raigad district on Wednesday at 11.30 am is an indication of an increasing frequency of severe cyclones developing in Arabian Sea in the past decade, a trend that studies have linked to climate change.
In the past two years, there have been seven cyclones in the Arabian Sea, though, according to India Meteorological Department (IMD), the ratio of cyclones in the Arabian Sea and the Bay of Bengal — which just witnessed the destructive cyclone Amphan on May 21 — is 1:4.
The Intergovernmental Panel on Climate Change (IPCC) last year came out with a special report, Ocean and Cryosphere in a Changing Climate, in which it said that extreme rainfall and extreme sea level events associated with some tropical cyclones are being seen to have a cascading impact on coastal areas.
“There is emerging evidence for an increase in annual global proportion of Category 4 or 5 tropical cyclones in recent decades,” the IPCC report had said.
A category 4 cyclone has a wind speed of 209-251 kmph, and is referred to as an extremely severe cyclonic storm, while a category 5 cyclone has a wind speed of more than 252 kmph, and is referred to as a super cyclone.
The IPCC report refers to a 2017 study led by Atmospheric and Oceanic Sciences Program, Princeton University, USA, which found that in 2014 and 2015, post-monsoon extremely severe cyclonic storms (ESCS) were first observed over the Arabian Sea causing widespread damage.
The study had concluded that climate change had led to an increase in the occurrence of ESCSS in the Arabian Sea.
“The effect of climate change on Cyclone Nisarga, my answer is “uncertain”. Our research suggests that cyclones would be more frequent during the post monsoon season (October-december) by a series climate model simulations. However, we didn’t find any significant changes in cyclone activity during the premonsoon (April-june) season through the climate simulations. It is very difficult to identify if a cyclone (like Nisarga) is generated in line with climate change,” said Hiroyuki Murakami, Project Scientist, University Corporation for Atmospheric Research, Geophysical Fluid Dynamics Laboratory. Murakami is the lead author of the study.
“Rising mean sea levels will contribute to higher extreme sea levels associated with tropical cyclones (very high confidence). Coastal hazards will be exacerbated by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones,” the IPCC report further stated.