Japan will monitor the long-term climate repercussions of Saturday’s huge undersea volcanic eruption in the South Pacific in case they have an impact on the country.

“We don’t know if (volcanic) aerosols will reach the stratosphere and affect the weather,” said Naoyuki Hasegawa, director-general of the Meteorological Agency, in a news conference on Wednesday. “We will monitor if there will be such change.”

Saturday’s disaster near Tonga reminded some of a similar event in the Philippines thirty years ago — an eruption that may have led to poor crop yields in Japan, thanks to a colder summer two years later.

In June 1991, the Philippines’ Mount Pinatubo erupted — one of the biggest volcanic eruptions of the century — throwing millions of tons of sulfur dioxide emissions into the stratosphere, which led global temperatures to temporarily drop by 0.5 degrees Celcius, Hasegawa said.

Two years later in the summer of 1993, rice crops were exceptionally poor, with the rice-crop index falling to 74, meaning the harvest was only 74% of an average year’s crop.

The agency said it is also monitoring the volcano via the meteorological Himawari satellite, though it is difficult to detect beforehand whether another eruption is about to occur.

Asked about the late response in issuing a tsunami warning, Hasegawa said the agency plans to establish a panel of experts to determine ways to improve the system, in addition to analyzing Tonga’s volcanic eruptions and any long-term effects.

The volcano erupted at around 1 p.m. Japan time on Saturday. At 7:03 p.m. that evening, the weather agency announced that no impact was expected other than a small change in sea levels. Yet at 11:55 p.m. a 1.2-meter tsunami was detected approaching the Amami islands in southern Japan, prompting the agency to issue a tsunami warning at 12:15 a.m.

The agency had detected a rise in tide levels along the Pacific coast from around 8 p.m. But since the tidal changes came 2½ hours earlier than the agency expected, and did not match the characteristics of a tsunami, agency officials were unsure if it was caused by the eruptions, which led to the delay.

“We will consider how we can alert the public beforehand,” said Hasegawa.

On Monday, Chief Cabinet Secretary Hirokazu Matsuno said he has instructed the agency to review its response to the eruption.

Experts have said that the tidal wave was caused by a repeated shock wave known as an “air tremor” that pushed the sea level down and raised the tide level in coastal areas when it hit Japan. Tsunami were detected in other parts of the Pacific region, including Peru.

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