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The first half of this year marked the hottest six months since modern weather observation began in Japan in the late 19th century, an analysis of official data showed.

And July is on track to be the hottest month on record, according to data from the Japan Meteorological Agency studied by The Asahi Shimbun.

“Global warming is clearly a contributing factor,” a JMA official said.

The Asahi Shimbun calculated the average temperatures for every day since 1898. It conducted the analysis under JMA oversight.

It used records from the 15 observation stations nationwide that the agency relies on when calculating average temperatures.

The average temperature for the six-month period from Jan. 1 to June 30 of this year was 12.14 degrees, surpassing the previous record of 12.02 degrees set in 2020.

It was particularly warm in March, when the days averaged 10.36 degrees, well above the previous record of 9.99 degrees in 2021.

June was the second highest on record and April was the fifth, pushing up the overall average for the first half of the year.

So far, July also has been hotter than any on record. The national average to July 25 was 25.42 degrees, exceeding the previous record of 25.30 degrees in 1978. With sunny days to continue in the forecast, the month is likely to be the hottest yet.

Global warming and other factors have driven up average temperatures by about 1.7 degrees over the past 120 years.

In particular, the last four years have all been in the top 10 for average January-June temperatures.

An explanation for the rise inevitably cites global warming. But there is also a technical reason why the heat soared this year.

“The atmosphere around Japan is heating up due to global warming. In addition, cold air did not descend as much in the spring this year,” said Masayuki Hirai, senior coordinator for climate information at the JMA. “This pushed up the average temperature.”

The JMA’s 15 observation stations are in areas that are largely unaffected by heavy urbanization. They include Abashiri in Hokkaido, Choshi in Chiba Prefecture, Iida in Nagano Prefecture, Miyazaki city and Ishigakijima island in Okinawa Prefecture.

But city residents have it the worst.

The Asahi Shimbun examined data from four observation stations in urban areas: Tokyo’s Chiyoda Ward, Nagoya’s Chikusa Ward, Osaka’s Chuo Ward and Fukuoka’s Chuo Ward.

It found that the average temperature in metropolises for the first half of this year was 14.47 degrees, surpassing the previous record of 14.41 degrees in 2021.

Average temperatures in urban areas have risen 3 degrees over the 120-year period.

This is due to the heat island effect, in which vast areas of ground covered with asphalt trap warmth from the sun. Moreover, heat also is emitted from air conditioners and automobiles.

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