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ClimateSeverity: High

Urban heat in Tokyo

The combination of global warming and a strong urban heat island makes Tokyo's summers increasingly dangerous.

Tokyo · Japan

01 · The problem

What is happening

The Japan Meteorological Agency documents a long-term rise in Tokyo's mean temperature that is larger than the national average rise, reflecting both global warming and the urban heat island effect. Hot, humid summers bring increased emergency transport for heatstroke, especially among older people. The city has promoted heat countermeasures including cool pavements, green roofs and misting, and Japan's national heatstroke alert system warns the public of dangerous conditions.

High severity. Serious, widespread effects requiring sustained action. Severity is descriptive editorial metadata summarising documented effects. It is not a measured index or a score.

02 · Causes

Why it is happening

  1. 01

    Global warming

    Rising background temperatures increase the frequency of extremely hot days.

  2. 02

    Urban heat island

    Dense buildings, paved surfaces and waste heat from air conditioning and traffic warm the city.

  3. 03

    High humidity

    Humid air limits the body's ability to cool through sweating.

03 · Impacts

Who and what it affects

  1. 01

    Heatstroke

    Emergency hospital transport for heatstroke rises during hot spells.

  2. 02

    Risk to older people

    An ageing population increases the number of people vulnerable to heat.

  3. 03

    Energy demand

    Cooling demand peaks during heatwaves, stressing electricity supply.

04 · Solutions

Documented approaches

  1. Heatstroke alerts

    National alerts issued by the Ministry of the Environment and JMA.

    Expected effectSupports timely protective behaviour and cooling shelters.

  2. Green and cool surfaces

    Rooftop greening requirements, heat-reflective pavements and street trees.

    Expected effectLowers surface temperatures locally.

  3. Tokyo Cap-and-Trade Program

    Since 2010, large buildings in Tokyo have faced mandatory emissions caps.

    Expected effectReduces emissions from large facilities and drives efficiency upgrades.

Explore an illustrative What-If

05 · Key indicators

What can be measured

No reliable quantitative indicator is included for this issue. TerraLens shows figures only where a credible source supports them — consult the sources below for current data.

06 · Sources

Where this comes from

  1. [1]Japan Meteorological AgencyGovernment of Japanjma.go.jp(opens in a new tab)
  2. [2]Ministry of the EnvironmentGovernment of Japanenv.go.jp(opens in a new tab)
  3. [3]Bureau of EnvironmentTokyo Metropolitan Governmentkankyo.metro.tokyo.lg.jp(opens in a new tab)

Links open the publishing organisation's site. Some point to the publisher's main page, where the named report or dataset can be found.

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