Human activity is responsible for just over half the thermal energy that causes the so-called heat island effect in central Tokyo, according to an Environment Ministry report released Tuesday.

The remaining urban warming is generated by asphalt, buildings and other landscapes altered by people.

Thermal energy produced by human activity accounts for the equivalent of 51.5 watts per sq. meter in the metropolis’ 23 downtown wards, with 47 percent of this stemming from heat expelled from buildings, such as that from air-conditioners, and 21 percent from automobiles, officials said.

The report expounds the concept of heat management through the use of a climate atlas that outlines wind patterns, direction and temperature trends.

To this end, the ministry is looking to set up a number of wind measurement stations around the Kanto area next year. In addition, an intraministry meeting to streamline and prioritize heat island measures will convene for the first time later this week.

In Tokyo, Chuo Ward emitted the most thermal energy with 152.3 watts per sq. meter, followed by Chiyoda, Taito, Shinjuku and Minato wards. Koto Ward registered 94.3 watts per sq. meter, the least heat emitted, due to the high percentage of open water, officials said.

The report, which includes a case study of Minato Ward, speculates that the area is unduly hot because a wall of skyscrapers impede Tokyo Bay winds from flushing warm air out of the area.

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