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2. Summary of future projections

Projected changes over Japan for the end of the 21st century (future climate: 2076-2095 average) relative to the 20th century (present climate: 1980-1999 average) are summarized below.

Projected changes in temperature

The annual mean temperature is projected to increase by about 3C in all regions. In particular, the northern part of Japan is expected to see the most significant rise (more than 3C). For all regions, the increase in temperature is projected to be the largest in winter and the smallest in summer. In winter, the rise is expected to exceed 3C in most regions except Okinawa/Amami. In particular, an increase of more than 3.5C is expected in northern and eastern parts of Japan.

Fig. 2.1-1 Regionally averaged changes (left) and spatial pattern of changes (right) in annual mean temperature In the panel on the left, the red bars indicate future changes and the thin black lines show the standard deviation of interannual variability (left: present; right: future). In the panel on the right, red indicates increase and blue indicates decrease.

Fig. 2.1-2 Regionally averaged changes in seasonal mean temperature (left: summer; right: winter) The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

The 20-year return value (see Table 1.2-1) of annual maximum temperature is projected to increase within the range of 2-3C, with the largest rise on the Pacific side of northern Japan. The 20-year return value of annual minimum temperature is projected to increase in the range of 2.5-4C, with the largest rise also on the Pacific side of northern Japan.

Fig. 2.1-3 Regionally averaged changes in 20-year return values of annual maximum temperature (left) and annual minimum temperature (right) The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

The annual number of days with daily minimum temperatures below 0C is projected to decrease in all regions, especially in the northern part of Japan. The annual number of days with daily maximum temperatures above 35C is projected to increase from the eastern part of Japan to Okinawa/Amami, while the increase is expected to be relatively small in the northern part of Japan.

Fig. 2.1-4 Regionally averaged changes in the annual number of days with daily minimum temperatures below 0C (left) and with daily maximum temperatures above 35C (right) The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

2.2 Projected changes in precipitation

Annual precipitation averaged over Japan and for northern parts of Japan is projected to increase. Precipitation on the Pacific side of Japan is expected to increase from winter to spring.

Table 2.2-1 Regionally averaged changes in annual and seasonal precipitation (in mm) Light blue indicates that the change is larger than interannual variability in the present climate period. Grey indicates that the change is not significant at a 90% confidence level.

The frequency of intense precipitation is projected to increase in most regions. The number of dry days with daily precipitation of less than 1 mm is also expected to rise.

Fig. 2.2-1 Regionally averaged changes in annual frequency of hourly precipitation exceeding 50 mm (left) and annual number of dry days with daily precipitation of less than 1 mm (right) Left: The grey (red) bars show frequency in the present (future) period, and the thin black lines indicate the standard deviation of interannual variability. Right: The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

2.3 Projected changes in snow depth and snowfall

The annual maximum snow depth is projected to decrease in most regions, although it may increase in colder areas such as inland Hokkaido.

Fig. 2.3-1 Regionally averaged changes (left) and spatial pattern of changes (right) in annual maximum snow depth In the panel on the left, the red bars indicate future changes and the thin black lines show the standard deviation of interannual variability (left: present; right: future). In the panel on the right, red (blue) indicates decrease (increase).

The pentad maximum snow depth is projected to decrease not only in peak months but also in autumn and spring, indicating that the snowy season will become shorter in the future. Meanwhile, snowfall change around the peak of winter is not expected to be as clear as in early or late winter. The seasonal peak of maximum snow depth is projected to come earlier in winter in the future climate than in the present climate.

Fig. 2.3-2 Changes in seasonal variations of pentad maximum snow depth (left) and snowfall (right) The thick lines indicate pentad climatology (5-pentad running mean), and the shading denotes the interannual standard deviation. Black (red) corresponds to the present (future) climatology. The vertical axis shows anomalies from the annual mean of the present climatology.

2.4 Projected changes in other variables

Summer mean relative humidity is projected to decrease in most regions. Meanwhile, winter mean relative humidity is projected to increase in northern, eastern and western Japan except on the Sea of Japan side of eastern Japan.

Fig. 2.4-1 Regionally averaged changes in seasonal mean relative humidity (left: summer, right: winter) The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

Annual mean global irradiance is projected to decrease in the northern part of Japan. Winter (DJF) mean global irradiance is expected to decrease in most regions except Okinawa/Amami.

Table 2.4-1 Regionally averaged changes in annual and seasonal mean global irradiance (in MJ/m2) Light blue and orange indicate that the absolute value of change is larger than interannual variability in the present climate period. Grey indicates that the change is not significant at a 90% confidence level.

The potential for the occurrence of severe weather events such as gusting winds and thunderstorms (evaluated in terms of the Energy Helicity Index) is projected to increase in all regions.

Fig. 2.4-2 Regionally averaged changes in the annual mean Energy Helicity Index The red bars indicate future changes, and the thin black lines show the standard deviation of interannual variability (left: present; right: future).

1.5 Explanatory notes on figures << Previous page | Next page>> 3. Tables and figures

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