Come September and tropical storms in many places of the world begin to surge. This year, the first such big storm has been the Hurricane Dorian that has brought devastation to the Bahamas – a country within the Lucayan Archipelago in the Caribbean. Thousands of people of the Grand Bahama and Abaco Island have become shelterless, stranded in flooding, running out of food, drinking water and medicine. The UN has made an urgent appeal to the global community for immediate help to Bahamas.
In the words of the Bahamian prime minister Hubert Minnis, “We are in the midst of a historic tragedy. The devastation is unprecedented and extensive.” Minnis announced that the reconstruction would be a huge task and Bahama would need a massive coordinated effort.
The humanitarian disaster emerged after Dorian stalled over Bahamas for over 36 hours and left the five miles wide Grand Bahama devastated. Dorian also became a slow-moving storm, which has become a trend on part of the large storms lately. The slow-moving character of the storms makes them remain over a place for quite a long time and deluge it by torrential rains.
In recent times, the emergence of massive devastating storms has raised the concern of probable link of climate change with these devastating events. While tropical storms have been a phenomenon that occurs at regular interval with some massive destruction in between, the recent trend of these storms is very concerning. Invariably, for some years, any tropical storm takes the form of a massive one. Last year also, around the same time, hurricane Florence devastated parts of USA and typhoon Mangkhoot stormed the other side of the globe – Philippines. Scientists now have come to a conclusion that the man-made climate change has contributed to the consistent strength of the storms and the resultant destruction and humanitarian crisis.
The first thing ascribable to the strength of the storms is the warming of the sea. The basic physics says that the warm waters fuel storms. When a storm passes over warm water, its intensity abruptly increases. The sea surface temperature is increasing with global warming and to add to the crisis, deeper water is also getting warmer. A storm is weakened by the up-welling of colder and deeper water. When man-made climate change has also made the deeper water warmer, hurricanes often continue to intensify to a scale much higher than what should have been, according to the initial conditions of the storm. Moreover, the increased temperature of the sea surface and the consequent huge amount of moisture that becomes available in the air would make the rains more devastating. Going by the current trend, a storm leaves heavy intensity downpour and massive deluges.
This was the case with Dorian as well. Dorian was strengthened by waters well above the average temperature. Sea surface temperatures were more than 0.5 degree Celsius to 1 degree Celsius than the normal level of temperature in the region where Dorian started.
A study published in Nature a decade back estimated that there have been a 7% increase in maximum sustained wind speed for each 1 degree Celsius of warming. Again, scientific estimates say that destructive potential is proportional to the third power of the wind speed. This means that 7% sustained increase in wind speed would lead to 23% devastations.
The other concerning issue is the slow-moving character of the massive storms. As an outcome, a storm, after its landfall, spends many hours in a place with massive wind speeds, extremely heavy rains, widespread loss of lives and properties. A study published on June 3 in the journal Nature, reveals that climate change has made Atlantic storms to stall and move slowly. According to the study, this trend has emerged since the mid-20th century.
“This is yet another example of the kind of slow-moving tropical systems that we expect to see more often as a response to climate change. Upper-level steering winds are slowing over the continents during summer, so stalling weather systems are more likely”—says Jennifer Francis, a scientist with the Woods Hole Research Centre.
What we are now witnessing in the Bahamas is the combination of all the factors and more importantly, caused by man-made climate change, especially the warming of the planet. But, there is no sign of decreasing the release of carbon to the atmosphere and hence there seems no immediate indication of getting rid of the devastating storms.