Figure 1-4: Yearly mean temperature anomalies in Japan

Note 1: The data is based on the past observation records of monthly mean temperatures in Abashiri, Nemuro, Suttsu, Yamagata, Ishinomaki, Fushiki (Takaoka City), Nagano, Mito, Iida, Choshi, Sakai, Hamada, Hikone, Miyazaki, Tadotsu, Naze and Ishigakijima.

Note 2: The bars indicate anomalies against normal (for thirty years from 1971 – 2000 average of the 17 stations).

Note 3: The red line indicates a long-term linear trend.

Source: Compiled by the Ministry of the Environment based on the Japan Meteorological Agency data.

Figure 1-5: Annual Average Temperature Anomalies in Tokyo

Note 1: The bars indicate anomalies against normal (for thirty years from 1971 to 2000).

Note 2: The red line indicates a long-term linear trend.

Source: Compiled from the Japan Meteorological Agency data by the Ministry of the Environment.

in 2001 explains globally it is very likely that the 1990s was the warmest decade in the instrumental record (1861–2000), but annual global mean temperatures on record since 2000 exhibit an trend that exceeds the 1990s pace.

Japan also experiences a long-term upward tendency as to annual average surface temperatures, at a rate of $ 1.07^{\circ} $ C per 100 years. Especially in and after the 1990s, we have had many warmer-than-normal years (Figure 1-4).

The data in Figure 1-4 is based on the past observation records of monthly mean temperatures in seventeen geographically scattered non-urbanized locations nationwide, selected from those that have a meteorological observatory and a history of continuous weather observation since 1898. In urban areas, due to the heat-island phenomenon and other urbanization impacts, the upward trend is more prominent (Figure 1-5).

Such changes, estimated to be caused by increasing atmospheric $ CO_{2} $ concentration and rising temperature, have been emerging here and there in various places in the world.

### a. Extreme hot weather

In the summer of 2003, the central and western areas of Europe suffered a heat wave of unprecedented magnitude. More than 10,000 people died in France, and throughout Europe, the death toll exceeded 50,000 people. In Zurich, Switzerland, the monthly mean temperature in June was $ 6.9^{\circ} $ C higher than in a normal year. From the end of 2006 to the beginning of 2007, almost all areas in the Northern hemisphere experienced a warm winter. Global monthly mean temperatures in December 2006 and January 2007 registered record highs respectively since 1891. It is estimated that such extreme phenomena are attributed to global warming as a result of increasing GHGs.

Figure 1-6: Changes over time of the number of heat-illness victims in Japan

Source: Compiled from the Japan Meteorological Agency data by the Ministry of the Environment.

## Column : Introduction of “Extreme Heat Day”

The Japan Meteorological Agency establishes definitions for temperature-indicating meteorological terms used in weather reports. For example, a “frost day” is a day with a daily minimum temperature below $ 0^{\circ} $ C and a “tropical night” is a night without cooling down below $ 25^{\circ} $ C. For terms indicating hot weather, a “summer day” and a “heat day” are days with daily maximum temperatures of $ 25^{\circ} $ C or higher and $ 30^{\circ} $ C or higher, respectively. From April 2007, the Agency introduced a new summer term, an “extreme heat day”, to define a day with a high of $ 35^{\circ} $ C or higher. This reflects the frequently broken records of highs mainly in urban areas.