Major tropical cyclones have become ‘15% more likely’ over past 40 years


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.

Whirlwind

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.

The sparks & swirls of Arthur. The first tropical storm of the 2020 Hurricane Season. pic.twitter.com/kdoeyf7Olr — Dakota Smith (@weatherdak) May 17, 2020
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.”

Stormy world

The research finds that, from 1979-2017,...

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