Experts Predict 'super Typhoons' Could Strike Japan Due To Global Warming

Experts predict 'super typhoons' could strike Japan due to global warmingExperts are warning that global warming could bring with it Japan's first exposure to devastating "super typhoons."
In November 2013, Leyte Island in the Philippines was hit by one such typhoon, named Haiyan (Yolanda in the Philippines). It raised sea levels by 1 to 2 meters over the course of one minute, causing immediate flooding of buildings. One man who escaped by breaking through a glass window remarked that it was like a tsunami.

Despite their frequent exposure to typhoons, Filipinos had not envisaged the sheer strength of Typhoon Haiyan. Over 7,000 people died or went missing in the disaster.

The U.S. military's Joint Typhoon Warning Center defines a super typhoon as one where sustained wind speeds near the ground are on average over 67 meters per second over one minute. Applying the Japanese measurement standard, which is based on a 10-minute average, the figure works out at 59 meters per second.

Disastrous typhoons in Japan's past, such as Typhoon Ida in 1958, Typhoon Vera in 1959 and Typhoon Nancy in 1961, met these criteria before landfall, but by the time they arrived were no longer "super."

Many experts, however, warn that at around the end of this century there may be super typhoons that make landfall on Japan while retaining their "super" status.

Kazuhisa Tsuboki, professor of meteorology at Nagoya University, compares a typhoon to a car, calling the eye the "engine," and the water vapor it takes up the "gasoline." When water at the ocean surface is over 26 degrees Celsius, some water evaporates and is sucked up into the typhoon. The air in the eye is heated and becomes lighter, which further reduces air pressure. This boosts the flow of surrounding winds into the eye, which strengthens the typhoon.

The waters around the Philippines when Typhoon Haiyan hit were 29 degrees Celsius. In September and October, the waters around Japan do not go above 26 degrees Celsius, so typhoons during that period weaken as they pass these waters, but if global warming progresses, the situation will change.

Tsuboki calculated a scenario in which the average air temperature of the world at the end of this century is 2.8 degrees Celsius higher than it was at the end of last century. He determined that a super typhoon with central air pressure of 857 hectopascals and wind speeds of 88 meters per second, more powerful than Typhoon Haiyan, would form. The scenario also showed a number of typhoons nearly as powerful as that super typhoon making landfall on Japan.

"We need to raise the level of what we consider a worst-case scenario, and create (evacuation plans)," says Tsuboki.

What kind of damage would a super typhoon create? Looking at disastrous typhoons of the past, the threat of raised seawater levels is clearly a danger.

While super typhoons are characterized by their high wind speeds, sea levels during typhoons rise by around a power of two compared to wind speed. A doubling of wind speed could mean a quadrupling of the rise in sea height. When Typhoon Vera hit, sea levels rose by up to 3.55 meters, and over 4,500 people died or went missing in Aichi and Mie prefectures. Typhoon Bart in 1999 raised the water level in the Yatsushiro Sea of Kumamoto Prefecture, killing 12 people.

A group including Nobuhito Mori, associate professor of coastal disaster-prevention construction at the Disaster Prevention Research Institute of Kyoto University, ran a simulation that showed that a rise of over 4 degrees in air temperature would raise the frequency of a 2.5 meter increase in the sea level in Osaka Bay from once every 200 years to once every 50 years. A 2.5 meter rise is about what the city of Osaka experienced when Typhoon Nancy struck and flooded over 30 square kilometers of the city.

Mori says that in the 2013 typhoon at Leyte Island, the sea level rise was twice as high, at 5 meters. He says he also found records showing that around 6,000 people there died in the latter half of the 19th century as a result of higher sea levels.

"A huge rise in sea level is not something you experience often, and it is dangerous for us to rely solely on our memories and the memories of those around us," Mori said. "It is important to build breakwaters and teach people to use available weather information to make their own risk judgments."