Is Bengal Cyclone Evidence of More Climate Fueled Superstorms?

May 18, 2020


After a spectacular bout of rapid intensification on Sunday, Tropical Cyclone Amphan poses a grave storm-surge threat to the highly vulnerable coastline of the upper Bay of Bengal. The Joint Typhoon Warning Center (JTWC) upgraded Amphan to the equivalent of Category 5 strength at 2 am EDT Monday, with top 1-minute sustained winds estimated at 140 knots (160 mph). Update: As of 11 am EDT Monday, JTWC is rating Amphan’s top winds at 145 knots (165 mph).

On the scale used by the Indian Meteorological Department (IMD), Amphan was upgraded at 3 am EDT Monday to the highest possible level: super cyclonic storm. Only a handful of storms—about one per decade—achieve this level, which corresponds to a three-minute-averaged wind speed of 120 knots (140 mph). Hurricane ratings by the National Hurricane Center and JTWC are based on one-minute averaging, which will yield higher wind speeds for a given storm.

Amphan took advantage of very favorable conditions in the southern Bay of Bengal to strengthen incredibly quickly over the weekend. Drawing on very warm sea surface temperatures of 31°C (88°F), high oceanic heat content, and light wind shear, Amphan bolted from minimal tropical storm strength (35 knots or 40 mph) to Category 5 equivalent strength (140 knots or 160 mph) in just 48 hours—and from minimal hurricane strength (65 knots or 75 mph) to Cat 5 equivalent strength in just 24 hours.

Carbon Brief:

Tropical cyclones across the world have become more intense over the past four decades, a new study concludes.

Major tropical cyclones with winds of 115 miles per hour or more became 15% more likely at a global level from 1979-2017, according to the analysis.

The region seeing the most significant increases in cyclone intensity was the North Atlantic. Over the study period, the chances of a major hurricane occurring in the North Atlantic increased by 49% per decade, the research finds.

The southern Indian Ocean also saw large increases in cyclone intensity, the research finds. This is particularly notable because cyclones that originate in this region often strike in parts of coastal Africa that have limited natural hazard defences, a scientist tells Carbon Brief.

The results “should serve to increase confidence in projections of increased tropical cyclone intensity under continued warming”, the study authors say.


Tropical cyclones are storms that develop in tropical waters at least 5-30 latitude north or south of the equator, where sea temperatures are at least 27C. Strong tropical storms are called “hurricanes” in the North Atlantic and the central and North Pacific, “typhoons” in the northwest Pacific and simply “tropical cyclones” in the South Pacific and Indian Ocean.

Scientists have reasoned that climate change is likely to make tropical cyclones more intense. This is because tropical cyclones use warm, moist air as fuel and, as climate change warms the oceans, there is potentially more of this fuel available.

However, it is not easy to see a clear increase in intensity just by looking at the global tropical cyclone record, explains study lead author Dr James Kossin, an atmospheric research scientist at the National Oceanic and Atmospheric Administration (NOAA). He tells Carbon Brief:

“The historical tropical cyclone record is created in a real-time operational setting, typically by forecasters while a storm is active. The forecasters always use the very best data that they can get to estimate storm intensity. The problem is that the data have become progressively better over time. New instruments, data, and intensity estimation techniques are frequently introduced or updated and this creates an artificial trend.”

Instead, for the new research, published in the Proceedings of the National Academy of Sciences, Kossin and his colleagues made use of algorithms that can estimate tropical cyclone intensity from satellite data alone. Kossin explains:

“This removes a lot of the technology-based trends, but leaves the actual physical trends alone.”

The research finds that, from 1979-2017, the chances of a major tropical cyclone occurring increased by 15%. Tropical cyclones are considered “major” once their winds reach 100 knots – around 115 miles per hour – or more. This is equivalent to category 3 or higher on the Saffir-Simpson Hurricane Wind Scale.

The results provide a reliable indicator that tropical cyclone intensity is increasing, Kossin explains:

“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.”

4 Responses to “Is Bengal Cyclone Evidence of More Climate Fueled Superstorms?”

  1. Anthony William O'brien Says:

    Where did that come from? There was nothing of interest in the Indian Ocean a few days ago (well maybe three or four)

  2. redskylite Says:

    Worst possible time as shelters are in use with covid-19 quarantined.

    “As the governments of Bangladesh and the Indian state of West Bengal brace for Super Cyclone Amphan, millions of people living along the coast must be moved to safer places. But the cyclone shelters are already almost full with quarantined migrant workers who have returned due to the lockdown forced by the Covid-19 pandemic.”

  3. rhymeswithgoalie Says:

    Even without a direct hit, those poor bastard Rohingya refugees in Bangladesh just can’t get a break.

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