The Arabian Sea is witnessing more furious cyclones, putting Pakistan, India, Oman and Yemen at risk. This increasing incidence of cyclones is not only attributed to natural factors but exacerbated by global warming and massive deforestation.

"The Arabian Sea has recently seen a surge in intense storms. They usually form in the southeastern part of the sea, near India's western coast. Fortunately, almost half (48.5%) of the cyclones weaken and disappear without reaching land. However, about one-third of the storms head towards India, Oman and Yemen being the most affected countries."

Oman's long coastline along the Arabian Sea makes it vulnerable to cyclones, with storms striking the country once every three years on average. Cyclone Gonu, struck Oman in 2007, Phet in 2010, Nilofar in 2014, Megh and Chapala in 2015. The latter was the second-strongest cyclone on record in the Arabian Sea. Yemen is less frequently affected but still experiences significant damage and loss of life.

The Sindh and Balochistan coasts have also suffered disasters. The 1999 Pakistan cyclone (02A) was a deadly tropical cyclone that killed over 6,000 people and affected over 2 million in Thatta and Badin. Near the storm's centre, wind gusts were estimated to have reached 275 km/h. It was the most intense cyclone ever recorded in the region since record keeping began.

This record was however bypassed by Super Cyclonic Storm Gonu that struck the easternmost tip of Oman early on June 6, 2007, but caused strong gusty winds and torrential rainfall in Pasni and Ormara and left a trail of destruction. Few days later on June 21, the devastating Cyclone Yemyin (2007) unleashed its fury in Ormara,Pasni killing 730, with 300,000 fleeing for their lives. The storm’s wrath left nothing but destruction in its wake that would be remembered for years.

In 2017, The New Scientist published a study by Hiroyuki Murakami a Princeton University scientist, who established that “intense cyclones increased from 1979-2010 during the late monsoon season in this region due to anthropogenic (manmade) changes. “Continued manmade black carbon particles and sulphate emissions amplify the risk of cyclones in the Arabian Sea, the team concluded.

They found the aerosol emissions to have increased sixfold since the 1930s, leading to a weakening of the monsoonal circulation. Murakami and his colleagues used a sophisticated climate model to compare conditions in 2015 to conditions in 1860 when humanity’s carbon footprint was much smaller. They found a 64 per cent increased hurricane risk in the Arabian Sea.

Advisor to China Pakistan Joint Research Centre at Quaid-e-Azam University in Islamabad, Dr Ghulam Rasul says tropical cyclones “in South Asia, usually form in the Bay of Bengal because its sea surface temperature (SST) remained higher ie 26-28°C (79-82°F) than that of the Arabian Sea.” “Due to climate change “The Arabian Sea’s temperature is now higher than or equal to the temperature of the Bay of Bengal, 28-30°C (82-86°F) ,” he said. "The SST is the steering force of the cyclone," he said.

The temperature of the Arabian Sea began to increase noticeably around the early 2000s. In 2005, it rose above 28°C (82.4°F) for the first time, making it more conducive to cyclone formation. The warming trend accelerated further and in 2010 SST was ‘consistently’ above 28°C (82.4°F). This is believed to have contributed to a five-fold increase in the occurrence of "most intense cyclones", he suggested. With global warming, increasing deforestation and ever-increasing concentration of greenhouse gases in the atmosphere, "time is not far away when the coastal areas of Pakistan will have ever more cyclonic landfalls," warns Dr Ghulam Rasul.

Chief Meteorologist Sindh Dr Sardar Sarfraz said Cyclone Biparjoy of June 2023 was formed when the sea surface temperature was 32 C. The last week’s cyclone formed with a sea surface temperature of 28 C -29 C. Following the change in temperature regime, the Arabian Sea now produces 2-3 cyclones/year while the Bay of Bengal witnesses 3-4 cyclones/year. In contrast, the Red Sea and the Mediterranean Sea have lower SSTs and consequently fewer cyclones. The Pacific Ocean has a higher incidence of cyclones, but they are more dispersed across a larger area. SSTs are just one factor influencing cyclone formation.

Another important factor that helps cyclones to form is the wind shear, which is the change in wind direction and speed from the surface to the top of the atmosphere. The Princeton University climatologists think that previously the wind shear in the Arabian Sea was stronger than in the Bay of Bengal. This kept new cyclone development at bay and only “fewer” cyclones were formed in the Arabian Sea." However now the man-made changes have considerably weakened the wind shear making the Arabian Sea vulnerable to cyclones, they concluded.

Another critical factor contributing to cyclone formation is the Coriolis force that provides the cyclone its spin. Dr Ghulam Rasul defined the Coriolis force “as an invisible force that happens because of earth’s spin. It makes air and water, curve.” In the Northern Hemisphere, the Coriolis force acts to the right of the direction of motion, while in the Southern Hemisphere, it acts to the left. “This is responsible for global wind patterns, ocean currents, tropical cyclones and shapes weather patterns,” he said. This force is at its maximum on the poles and zero at the Equator. The Arabian Sea's cyclone hotspot is located between 10° to 20° North latitude, a region ideal for cyclones to form, strengthen, and potentially head towards the coasts of India, Pakistan, Oman, and Yemen." Cyclones even form outside this range like the US. The Atlantic Ocean, Eastern Pacific Ocean, and Gulf of Mexico produce hurricanes or tropical cyclones that affect the United States.

The formation of Asna was the outcome of a pretty unusual monsoon wind system, says Chief Meteorologist Sindh Dr Sardar Sarfraz. Cyclones typically form over oceans, but in rare cases, they can develop over land. This phenomenon is known as a "land-based cyclone" or "inland cyclone." Cyclone Asna developed on August 29 as a deep depression “on land” 60 km northwest of Bhuj (India) and 80 km northeast of Naliya in Gujarat.

Cyclones are generally formed in pre-monsoon (May-June) and post-monsoon seasons (Oct-Nov), but this time around Asna struck in the middle of monsoon ie August. Dr Sarfraz described this as an extremely rare happening. Quoting studies, he described this to be the first time since 1981 that it formed in August in the North Indian Ocean region. It was also the first time in the Arabian Sea since 1976. In the last 132 years (1893- 2023) only 28 cyclones developed in August in Bay of Bengal. Of these four were formed in the Arabian Sea in 1944, 1966, 1976 and now 2024. Besides those forming in this month have always been short-lived. Likewise, Asna defused on the third day, the chief meteorologist said.

Most of the time the Arabian Sea cyclones make landfall in Gujarat, India rather than Pakistan: Topography is one reason, says Dr Ghulam Rasul. The western Gujarat coast of India has a relatively flat coastline, allowing cyclones to make landfall with minimal disruption. In contrast, Pakistan has a more rugged terrain, making landfall more difficult. According to him, the intense heat generated by Tharparkar and Rajasthan deserts produces a low pressure that develops a curvature and pulls the cyclone towards Gujarat.

However, if the cyclone enters the Northern Arabian Sea from the south of Mumbai it heads west towards the low-pressure regions along the long coast of Oman and Yemen and makes a landfall there, Dr Rasul said. However, this doesn't mean Pakistan is completely safe from cyclones."

As the region gets hotter, governments must take action to reduce the frequency of cyclones. Mangrove forests provide excellent coastal defence of Sindh and Balochistan. Their amount of coverage depends on storm intensity, sea level rise, and coastal geometry. Ideally, a continuous belt of mangroves along the coastline of both provinces, with a minimum of 1-2 kilometres (0.6-1.2 miles) width, can offer comprehensive protection. This would require restoring at least 10,000-20,000 hectares (25,000-49,000 acres) of mangrove forests.

It is also inevitable that sea encroachment for residential, and commercial development is given a second thought, particularly in areas with high cyclone risk and vulnerable communities. The federal and provincial governments must complement mangrove restoration with other measures of coastal defence like sea walls, dunes, and early warning systems to enhance overall resilience. Against this backdrop, deforestation must stop and sustainable plantations must be taken up to reduce the incidence of natural catastrophes.