Hurricane Idalia made its landfall on Florida’s Gulf Coast in August 2023, which proved to be more dangerous than the meteorologists had predicted. Initially, the meteorologists had predicted a near-normal Atlantic hurricane season, but as the worldwide surface ocean temperatures rose, the hurricane became stronger. The typical hurricane season has also been shifting with storms forming earlier and making landfall in regions outside the historic norm. This has been posing great risks for those cities that are unprepared for such storms.
According to scientists, climate change is making hurricanes more intense, with increased rainfall and stronger winds. About 90 per cent of the greenhouse gas (GHG) emissions have been absorbed by oceans leading to their becoming warm. This is also causing increase in the intensity of storms. As per researchers, the increase in the wind speed is due to the result of climate change which could further increase the proportion of the storms reaching the most intense levels.
This year, super cyclones and tropical cyclones have formed because of the surface temperatures of oceans being exceedingly warm.
When the ocean water warms up, and moist and humid air starts to blow, then hurricanes are formed. When warm seawater evaporates, its heat energy is transferred to the atmosphere leading to the storms wind to strengthen. This leads to the intensification of cyclones/hurricanes. Only a handful of storms in the Arabian Sea and the Bay of Bengal achieve the level of super cyclone, about one occurs every 10 years. According to a list maintained by Weather Underground, 26 of the 35 deadliest tropical cyclones recorded have occurred in the Bay of Bengal.
Hurricane, Cyclone, Typhoons
In ancient times, European explorers used the indigenous phrase ‘hurakan’ to signify evil spirits and weather gods, to describe the storms that battered the ships in the Caribbean. With time, these giant tropical storms with high-speed winds began to be called hurricanes. In the North Atlantic, central North Pacific, and Eastern North Pacific, these swirling storms are called hurricanes. In the South Pacific and Indian Ocean, these rotating storms are called cyclones. In the Northwest Pacific, they are known as typhoons.
If the speed of the wind exceeds 119 kilometres (74 miles) per hour, then it is termed a tropical cyclone. If the wind speed crosses 220 kilometres per hour, then it is called a super cyclone.
Climate Change and Hurricanes
According to meteorologists, climate change has been making hurricanes wetter, windier, and more intense. These hurricanes cause storms to travel more slowly. As a result, they dump more water in one place. Had there been no oceans, Earth would have become much hotter due to climate change. In the past four decades, oceans have absorbed about 90 per cent of the warming caused by heat trapping GHG emissions. Much of this ocean heat is contained near the surface of the water.
Tropical cyclones in the seas are common during the summer which help in the arrival of monsoon. However, ocean warming has become a global feature now, and this has made storm prediction less reliable and disrupted monsoon patterns. According to meteorologists, the worst places for storm surges tend to be shallow and concave bays. Water pushed by strong winds of a cyclone gets concentrated as the storm moves up the bay.
Climate change has also pushed up the amount of rainfall due to a storm because a warmer atmosphere has the capability of holding more moisture. This moisture forms water vapour and it keeps on building up till the cloud breaks. Heavy rainfall occurs as a result of the moisture-laden cloud break. In April 2022, the journal Nature Communications published its report on the impact of climate change on hurricanes. The study states that in 2020, during the Atlantic hurricane season, the rainfall rates rose by 8 per cent to 11 per cent because of hurricanes.
Human activities have warmed the world by 1 °C above the pre-industrial time (1850–1900) average. The US National Oceanic and Atmospheric Administration (NOAA) scientists predict that at 2 °C warming, the hurricane wind speed could increase by up to 10 per cent.
Categories of Hurricanes/Cyclones
According to the Saffir-Simpson hurricane wind scale (SSHWS), there are five categories of hurricanes in the order of increasing intensity. Category 1 storms usually cause no significant structural damage and the wind speed may range between 74 miles per hour (119 km/h) and 95 miles per hour (153 km/h). Very dangerous winds may produce some damage. Category 2 storms intensify and damage poor constructions. Extremely dangerous winds may cause extensive damage. In Category 2, wind speed may range between 96 miles per hour (154 km/h) and 110 miles per hour (177 km/h). Tropical cyclones of Category 3 are major hurricanes and may cause devastating structural damages. The wind speed may vary between 111 miles per hour (178 km/h) and 129 miles per hour (208 km/h). Category 4 hurricanes tend to produce extensive damages and irreparable damage. The wind speed may range between 130 miles per hour (209 km/h) and 156 miles per hour (251 km/h). Category 5 is the highest category of hurricane, which may cause catastrophic damage with a wind speed of more than 157 miles per hour (more than 252 km/h).
According to the NOAA, Category 4 or Category 5 hurricanes are most intense and could rise by about 10 per cent in this century. Since 1851 no storm of the intensity of Category 5 has happened.
Shifting Hurricane Season
Climate change is affecting the storms and typical season for hurricanes is shifting. This is also leading to hurricanes making landfall in regions which are unusual and far outside the historic norm. According to NOAA, since 1851, most of the hurricanes have made a landfall in Florida. However, some storms are reaching peak intensity and making a landfall farther north. According to scientists, this shift may be related to rising global air and ocean temperatures. This shift is a cause of concern for mid-latitude cities like New York, Boston, Beijing, and Tokyo. In fact, these cities do not have the infrastructure to meet the disasters caused by the landfall of hurricane and they are not prepared to meet the consequences of the storm.
According to the study published in August in the journal Nature Communications in North America, the normal timing of hurricane activity is from June to November. The hurricane activity usually peaks in the month of September. This is summertime build-up of warm water conditions. However, at present, those storms that used to make a landfall in the US are more than three weeks earlier than it used to be in 1900, nudging the start of the season into May.
Even in Asia, in the Bay of Bengal, the same trend is being seen over the years. Since 2013, cyclones have been forming earlier than usual. According to the November 2021 study in the Scientific Reports, in the recent times, it has been forming in April and May, which is much ahead of the summer monsoon. Having said all this, it is still unclear if climate change is affecting the number of hurricanes that form each year. According to the study published by a team of scientists in the journal Nature Communications, there has been a rising frequency for North Atlantic hurricanes. However, there is still no clear-cut evidence on this and the research is still going on.
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