10.1.2.2. Future Climate Projections

Global climate models project that the mean annual surface temperature will rise by about 1.0-3.5°C by the year 2100. On regional scales, confidence in future climate projections remains low. There is more confidence in temperature projections than in precipitation changes. The degree to which regional climate variability will change also remains uncertain. Projections of future changes in temperature and rainfall for the Temperate Asia region, based on available scenarios from various GCM experiments, are described below.

10.1.2.2.1. Temperature

GCM equilibrium response experiments suggested an annual mean warming of 2-5°C over the region as a result of a doubling of CO₂ (experiment acronyms A3, F1, G1, and H2 in Table 1-1 of the Introduction). Warming was projected to be more pronounced during winter than in summer. Subsequent numerical experiments with coupled AOGCMs, which included transient increases in greenhouse gases (i.e., increases in equivalent CO₂ at a rate of 1% per year), projected a slightly lower degree of warming over the region of between 2°C and 3°C at the time of CO₂ doubling on an annual mean basis (experiment acronyms X2, X5, and X7 in Table 1-2 of the Introduction). Warming was more pronounced in arid/semi-arid and Siberian regions than in the coastal monsoon region. Recent simulation experiments (experiment acronyms X6 and X8 in Table 1-2 of the Introduction), wherein GCMs also include the offsetting effects of sulfate aerosols, project a temperature rise of about 0.8°C over the eastern part of the region, about 1°C over most parts of eastern China, and close to 2°C in the Siberian region on an annual mean basis by the middle of the next century. During winter, the projected changes are marginally higher for all of the regions; during summer, however, the projected warming is considerably less, and most parts of China show a cooling. It should be noted that the projections that account for sulfate aerosols also are highly uncertain because our current understanding of the indirect effects of sulfate aerosols is poor (IPCC 1996, WG I, Section 6.2.2).

10.1.2.2.2. Precipitation

In equilibrium and transient-response numerical experiments with GCMs, precipitation is projected to increase marginally (<0.5 mm/day) at the time of doubling of CO₂ during the winter (DJF) throughout the region. In summer (JJA), the spatial pattern of projected changes in precipitation is not uniform over the region. Model projections suggest that precipitation will increase slightly (0.5-1.0 mm/day) in the northern part of the region (Siberia) and by more than 1 mm/day over the Korean peninsula, the Japanese islands, and the southWestern part of China. In contrast, precipitation changes show a decline in the northern, western, and southern parts of China (IPCC WG I, Section 6.2.2). The projected decline in rainfall over most of China is substantial in numerical experiments that include the effects of sulfate aerosols.

10.1.2.2.3. Possible changes in sea ice over the Sea of Okhotsk

Tokioka et al. (1995) studied possible changes in sea ice over the Sea of Okhotsk based on future climate projections using a coupled GCM (MRI-X3). Sea ice in the Sea of Okhtosk is most vulnerable to climate, and it influences climate, ecosystems, fisheries, and transportation around the area. Because this area is the southernmost ocean in the Northern Hemisphere where sea ice forms, a sea ice-albedo feedback may occur early and effectively. These results suggest an early disappearance of sea ice and thus a large sea-surface temperature (SST) rise over the Sea of Okhotsk. Therefore, it is plausible that this area will suffer large impacts of climate change in coming decades.

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