Last May, a study confirmed that climate change has been making tropical storms more intense. It has increased the chance that a cyclone develops into a Category 3 storm or higher by 8% per decade since the late 1970s. However, studying storms and tropical cyclones has been difficult because the tools scientists used to study them change constantly. While research has suggested the warming world would produce wilder and stronger storms, it’s been difficult to say that with certainty.
"The main hurdle we have for finding trends is that the data are collected using the best technology at the time. Every year the data are a bit different than last year, each new satellite has new tools and captures data in different ways, so in the end, we have a patchwork quilt of all the satellite data that have been woven together,” James Kossin, a National Oceanic and Atmospheric Administration scientist and University of Wisconsin-Madison professor, said in a statement.
Super Cyclone Amphan Displaces Millions of People
A recent example of how storms and tropical cyclones have changed is Cyclone Amphan, which walloped India and Bangladesh last May. Reports revealed that it became the most powerful storm ever recorded in the Bay of Bengal, the northeastern part of the Indian Ocean, with winds of up to 165 miles per hour. It also killed at least 84 people in the two countries, bringing "war-like" destruction to the city of Kolkata in the Indian state of West Bengal.
While three million people were successfully evacuated from India and Bangladesh, many villagers chose to stay in their homes in fear of being infected by the coronavirus. Hundreds of thousands of people also saw their homes destroyed. West Bengal chief minister Mamata Banerjee reported that two districts in Kolkata were completely destroyed. "We have to rebuild those districts from scratch. Area after area has been ruined. I have experienced a war-like situation today,” she said.
Bangladesh evacuated more people ahead of the storm compared to India, with 2.4 million compared to 660,000. "Even by Bangladeshi standards, this was a powerful storm. We've received reports that more than 5 million people were disconnected from the electricity grid for their own safety as winds of 150kph smashed into power lines, destroying homes and uprooting trees. In some of the worst-affected areas there was a tidal surge of nearly three meters, causing dams to overflow and submerging low-lying villages and crops,” Bangladesh Humanitarian Director Mostak Hussain said.
Tropical Cyclones Are Becoming More Common and Severe
A recent study published in the journal Proceedings of the National Academy of Sciences found a clear trend after studying an era when climate change dramatically accelerated: storms are getting stronger in general, and major tropical cyclones are coming more often. The researchers found that the world has significantly warmed every year for the past four decades. Those years included eight of the 10 warmest ever recorded.
According to Live Science, a science news website that features groundbreaking developments in science, space, technology, health, the environment, our culture and history, the researchers were able to create an extensive dataset of about 225,000 similar-quality images of around 4,000 global tropical cyclones stretching back to the disco era. They searched for the chances of any given tropical cyclone becoming a hurricane (hitting 65 knots) increasing.
Although finding trends about global tropical cyclones has traditionally suffered from inconsistent data records, the findings of this study are consistent with the theory that the increasing intensity of tropical cyclones is due to the climate crisis, specifically the rising sea-surface temperatures. It was also found out that these extreme weather events are becoming more common and severe in the Arabian Sea, central Pacific, and the North Atlantic.
Hiroyuki Murakami, a researcher from the University Cooperation for Atmospheric Research in Boulder, US, and colleagues used observations between 1980 and 2018 to quantify changes in tropical cyclone activity and high-resolution dynamical models to deduce the causes of change. The results showed that aerosols, greenhouse gas emissions, and volcanic eruptions have influenced the variability in the occurrence of tropical cyclone trends across different regions.
According to The Guardian, a British daily newspaper, the findings match the climate model predictions and the knowledge that increasing ocean temperatures gave tropical storms more energy. “This study confirms what the climate models have been predicting for some time – that the proportion of the most intense storms will increase as the climate warms,” Dr. Hamish Ramsay, a senior research scientist at CSIRO who studies cyclones, said.
The researchers also looked at the changes in cyclone intensity by region. They found out that there’s been an increase in the number of the more intense storms in the southern Indian Ocean and southern Pacific Ocean. “[The study] suggests that the climate change signal in the data is potentially already emerging and this is something that climate scientists have been saying for some time. We may be at a point now where we are starting to evidence from observational data that supports what the models have been telling us,” Ramsay said.
Scientists explained that tropical cyclones are fueled by warm, moist air. As climate change warms the oceans, there is potentially more of this fuel available. According to Carbon Brief, a UK-based website designed to improve the understanding of climate change, both in terms of the science and the policy response, the research also revealed that the chances of a major tropical cyclone occurring increased by 15%.
“Our analysis finds that the global increasing trend in tropical cyclone intensity has now risen to a point where it is very unlikely to be random, even after addressing known issues with the historical data,” Dr. James Kossin, an atmospheric research scientist at the National Oceanic and Atmospheric Administration (NOAA), said.
While human-caused warming is likely fueling the increase, the researchers said that there are also natural cycles at play as well. This could increase or decrease storm frequency and intensity varying from basin to basin and from year to year. "Like all aspects of climate, there is an element of natural variability at play. Our study does not formally disentangle the natural causes from the human-activity causes, and the trends we found are most likely due to a combination of both," Kossin added.