Mean surface air temperature in winter (Fig 3.1, Fig 3.2)
- Greater temperature increases in winter (December - March) are projected at higher latitudes for the end of the 21st century.
- The surface air temperature in winter is projected to increase more than 3°C in Hokkaido, 2 to 3°C from Tohoku to Western Japan, and about 1.5°C in Okinawa/Amami for scenario A1B.
- For B1, projected surface warming in winter is 1.5 to 2°C in Hokkaido and 1 to 1.5°C in other areas.
Temperature extremes in winter (Table 4.1, Fig 4.1)
- In Hokkaido, a decline of about 50% in the frequency of days with a maximum temperature of < 0°C relative to the present day is projected by the end of the 21st century for scenario A1B.
- The number of days with minimum temperatures of < 0°C is projected to decrease by almost half in Tohoku for scenario A1B.
- Projections indicate that the number of days with minimum temperatures of < 0°C decrease by up to 50% for scenario B1 and disappear almost entirely for A1B in Hokuriku, Kanto/Tokai and Western Japan.
- Precipitation in winter (December - March) is projected to increase around Japan (except around Okinawa/Amami) for the end of the 21st century.
- The projected increases of precipitation in winter are 10 to 30% relative to the present day in Hokkaido and on the Sea of Japan side of Tohoku for scenario A1B.
- Snowfall in winter (December - March) is projected to decrease under both scenarios A1B and B1, in most areas except Hokkaido. The projected decrease for scenario A1B is greater than that for B1.
- The projected increase in snowfall at high altitudes in Hokkaido for scenario A1B is greater than for the B1.
- The frequency of heavy snowfall is projected to increase at high altitudes in Hokkaido. The projected rate of increase for scenario A1B is greater than that for B1.
- In most areas except Hokkaido, the frequency of heavy snowfall is projected to decrease for scenario A1B more than that for B1.
- The sea surface temperature (SST) around Japan is projected to increase. The projected long-term trends of the SST during the 21st century are 2.0 - 3.1°C and 0.6 - 2.1°C per century under scenarios A1B and B1, respectively.
- The projected long-term SST trends in the Sea of Japan are greater than those in the seas south of Japan. Projected warming shows geographical patterns similar to those observed over the past century.
- The sea level around Japan is projected to rise. The projected long-term trends of sea level rise during the 21st century are 0.09 - 0.19m and 0.05 - 0.14m per century under scenarios A1B and B1, respectively. The contribution to sea level rise does not include losses from the ice sheets of Greenland and Antarctica.
- The projected sea level rise for scenario A1B is greater than that for B1 in every region.
- The projections for the volume transport and current position of the Kuroshio show no statistically significant trend with global warming.
- The projected current velocity of the Kuroshio shows a tendency to increase east of Japan by the end of the 21st century.
- The projection for future changes in the Kuroshio is uncertain at the present stage.
Sea Ice in the Sea of Okhotsk (Fig 11.1)
- The sea ice extent in the Sea of Okhotsk from January to April is projected to decrease by around 75% and 80% by the end of the 21st century under scenarios A1B and B1, respectively.
- The maximum sea ice extent observed in the Sea of Okhotsk during March is projected to shrink to about 75% and 80% by the end of the 21st century under scenarios A1B and B1, respectively.
- With global warming, a later onset of sea ice freeze-up in late autumn and an earlier retreat northward in early spring is projected in the Sea of Okhotsk.
