Cyclone Mocha- A stark reminder of the devastation of climate change
By Haider Ali
Tropical Cyclones (TCs) are becoming more intense and devastating. Bangladesh was still overwhelmed by the aftereffects of the devastating 2020 Cyclone Amphan (maximum intensity of 268.54 km/hr), but last month (on 14th May 2023), Cyclone Mocha broke the record for the strongest cyclone ever recorded in the north Indian Ocean in the satellite era (since 1982) tying with 2019’s Tropical Cyclone Fani. The storm, which formed over the southern part of the Bay of Bengal on 11 May, went through a rapid intensification from 65 km/hr to 120 km/hr on 12th May, to 213 km/hr the next day, hitting the coastlines of Bangladesh and Myanmar on 14th May, at around 15:00 local time, with strong winds reaching 278 km/hr, leading to heavy rainfall and storm surges. This has led to a worrisome situation in both countries, especially refugee camps. In Bangladesh’s Cox’s Bazar, the world’s largest refugee camp, around one million Rohingya refugees (half children) faced the severe consequences and have been left with flooded and damaged temporary shelters.
Life cycle of Cyclone Mocha, all times are in Myanmar Time (Credit: Global Disaster Alert and Coordination System)
Mechanism
Climate scientists provide evidence that this increased cyclone activity is strongly linked to global warming which has increased ocean temperatures and atmospheric moisture which act as catalysts for such storms. TCs are formed as a result of solar heating over the oceans between 5 and 30-degrees latitude. As the temperature reaches 27 ℃, the warm air rises quickly forming an area of very low pressure. As water vapour in the rising air condenses, it releases heat energy into the storm which acts as feedback to a chain reaction. Therefore, heat energy and moisture from the oceans act as fuel to drive and intensify TCs. As TCs reach the land surface (landfall), they bring storm surges, strong winds and torrential rain. Generally, after landfall TCs die out due to the dissipation of energy as they are cut off from the source. However, if atmospheric conditions on land are similar to the moist ocean environment, TCs maintain or even intensify in strength – this is known as the “Brown Ocean Effect”.
Home damaged by Cyclone Mocha in Cox's Bazar, Bangladesh (Credit: AP/AI-emrun Garjon)
Alarming Future
Proper planning and preparedness can help to reduce the worst impacts of extreme weather. With improved forecasting skill, efficient monitoring and disaster management efforts, the number of deaths during cyclones has significantly reduced in recent years. However, the risk to property and infrastructure has increased due to urbanisation and it is important to study the potential changes in the frequency and intensity of future TCs. Climate scientists use climate model outputs for such studies; however, their projected results can be biased by the limitations of these models. The climate modelling team (Dr Haider Ali and Prof Hayley Fowler) in the Living Deltas Hub based at Newcastle University have collaborated with the UK Met Office to conduct a study using the latest state-of-the-art climate models from CMIP6 HighResMIP over the Ganga-Brahmaputra-Meghna and Mekong river basins. Our study results show a decline in the frequency of TCs in the future but an increase in the most intense storms, in both basins. This means that these basins are at greater risk of future impacts from TCs. The biggest challenge is how these scientific results can be conveyed to locals, policymakers and government and used in policy making and preparedness. We are slowly moving along a road of preparedness to more intense future TCs, but need to make more rapid progress
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Read the full study here.
Read more in a news article here.
Other blogs you may like: Cyclone Amphan in Bangladesh: An Overview — Delta Hub