There have been no significant changes in the number of typhoons in the north-western Pacific Ocean over the past seventy years, that is, since reliable data has been available.

Atsushi Goto

"The annual number of typhoons, including intense ones, that have formed and moved towards Japan does not show a statistically significant trend in the period between 1951 and 2019."

The precise, measured words of Atsushi Goto, climate expert at the Japan Meteorological Agency (Jma), might come as a surprise, especially in light of the disasters recently caused by Maysak and Haishen, two typhoons that occurred just a few days apart. "However, we expect an increase in the intensity of these phenomena due to climate change," Goto adds. If until now Japan's typhoon season, concentrated in the months of August and September, has not changed significantly, the dark clouds on the horizon are more threatening than before.

What typhoons are and how they form

Typhoons, hurricanes and cyclones are different names for the same meteorological phenomenon, scientifically known as a tropical cyclone. It originates, as the name suggests, in the tropics: warm air rises from the oceans and results in the formation of clouds and winds that, fed by the heat of the oceans and the evaporation of water, give rise to the most violent storms on Earth.

These are considered tropical cyclones when winds reach 119 kilometres per hour and change name according to their geographical position. Typhoons concern the north-western Pacific Ocean region and strike Japan, South and North Korea, China, Taiwan, Malaysia, Singapore, the Philippines, Thailand, Laos, Cambodia and Vietnam.

Typhoons Haishen, Maysak and Hagibis

The first use of the English word "typhoon" dates back to 1588, and the term is thought to derive from the Chinese tai fung and the Hindustani ṭūfān, which in turn comes from the Persian word for storm. Typhoons are frequent phenomena, with which the populations of South-East Asia and East Asia have historically learned to live. But things are changing.

On 3 September, Maysak struck South Korea, where two people died, after causing several injuries on the Japanese island of Kyushu and, further south, the sinking of a cargo ship carrying 43 people (of whom three were rescued) and nearly 6,000 head of livestock. Haishen, meanwhile, made landfall, also in South Korea, on 7 September, leaving a trail of destruction in Japan: two dead, four missing, hundreds injured and two million people evacuated. The fact that these tropical cyclones occurred just a few days apart "is a rare occurrence, but it is not the first time," explains Goto.

The damage caused, however, pales in comparison to that of Hagibis in October 2019, one of the strongest typhoons to strike Japan in decades, which caused around a hundred deaths, tens of millions of euros in damage and the suspension of the Rugby World Cup. Even today the wounds left by the storm are visible in many parts of the country. The fact that the tropical cyclone occurred in October is not anomalous; "statistically it happens once every five years," Goto contextualises, but "it caused very severe flooding; I would never have expected the country, especially the eastern part, to suffer such damage. Usually when typhoons approach eastern Japan they are already weakening. Hagibis, on the other hand, maintained its intensity."

Climate change and tropical cyclones

"The energy source of tropical cyclones is water vapour in the atmosphere," explains Goto, who coordinates the international cooperation activities of the division dedicated to climate forecasting at the Tokyo Climate Center, the international arm of the Jma and one of the Regional Meteorological Centres of the World Meteorological Organization (Omm). "When water vapour becomes clouds and rain, it releases heat, which in turn drives the rotary motion of cyclones. A warmer atmosphere can hold more water vapour, and this is one of the mechanisms by which we expect tropical cyclones to intensify as a result of global warming."

Rising temperatures

In the meantime, temperatures are already rising. This August, ocean surface temperatures south of Japan were well above average according to the Jma. As for land temperatures, the national average has increased at a rate of 1.24 degrees Celsius per century, that is, above the global rate. And there is more. From the 1970s to the present day, "there has been a significant increase in the number of days in a year with more than 200 millimetres of rain, which we believe will continue to rise," explains Goto. "On the other hand, the total number of rainy days has decreased, which implies a greater risk of drought, landslides and flooding."

A resilient Japan?

Japan is particularly prone to natural disasters; typhoons, torrential rains, hydrogeological instability, and more besides. It is enough to note that there is a Japanese ministry for disaster management. It remains to be seen, however, whether the tenacity and capacity of its people to pick themselves back up even in the face of catastrophes — from which several resilience concepts characteristic of its culture emerge — also translate into resilience to climate change.

Particularly from the mid-twentieth century onwards, when a violent typhoon killed more than a thousand people in 1958, the country has undertaken major works to address the vulnerability of its territory, for example investing billions of euros to control the flow of virtually all its rivers and thereby reduce the impact of flooding. "But our infrastructure is based on historical rainfall statistics: this does not allow us to adapt to the climate change that is coming," explains Goto.

Engineering cannot be the answer to everything

Although the government is engaged in research into how to build new infrastructure based on future projections, engineering cannot be the answer to everything. This is demonstrated by the ineffectiveness of artificial embankments in containing the river flooding caused by the record rainfall of Typhoon Hagibis (for instance, nearly 90 centimetres of rain fell in 24 hours at the town of Hakone, southwest of Tokyo). The only real solution lies in addressing the causes of the intensification of extreme weather events. "Japan is not doing enough to mitigate climate change," according to Goto. For example, the country has yet to strengthen its Nationally Determined Contributions (Ndc) for emissions reductions, despite all countries being called upon to do so in order to meet the commitments of the Paris Agreement.

Awareness is not enough

"People in Japan are increasingly aware of the risks associated with climate change, but this has not necessarily translated into a change in lifestyle. Through my work I would like to bridge the gap between awareness and action," says Goto. Faced with the climate crisis, the scientist cannot remain neutral. "I am worried," he confesses. "According to the Jma, the frequency of heavy rainfall in the country could double by the end of the century. I hope our forecasts are wrong and that we will be able to rewrite the future instead. That is why I will keep studying climate change." But that is not enough. It is then up to citizens and institutions to act on the basis of Goto's observations and analyses, and those of all the other scientists who, like him, are sounding the alarm.

Typhoon statistics

The average number of typhoons that form in the northwestern Pacific Ocean area (formation), that move towards Japan (movement) and that make landfall in Japan (landfall). Period analysed: 1981–2010.

	Formation	Movement	Landfall
January	0.3	-	-
February	0.1	-	-
March	0.3	-	-
April	0.6	0.2	-
May	1.1	0.6	0.0
June	1.7	0.8	0.2
July	3.6	2.1	0.5
August	5.9	3.4	0.9
September	4.8	2.9	0.8
October	3.6	1.5	0.2
November	2.3	0.6	0.0
December	1.2	0.1	-
Annual total	25.6	11.4	2.7