Table 2.1: Temperature Scenario inSemarang City CCROM IPB, 2010
2000 2025
2050 2100
SRESA2: moderate 0.2
0.5 1.2
2.9 Range
0.15-0.25 0.3-0.7
0.8-1.6 2.0-4.1
SRESB1: moderate 0.2
0.7 1.1
1.9 Range
0.15-0.25 0.5-0.9
0.7-1.6 1.2-2.27
2.1.2. Rainfall
Based on 100 years rainfall CRU TS2.0 dataset, it is known that rainfall in Semarang City and number of rainy days is very volatile. However, in general it is known that rainfall increased in its intensity on
the wet season SON and DJF. In DJF, the seasonal rainfall increased approximately from 950 to 1000 mm, while in SON it increased from 250 to 300 mm see figure 2.5. The upward trends of rainfall
during wet seasons SON and DJF are associated with increasing trends of wet days frequency at the same seasons, from 44 to 47 days in SON and from 67 to 68 days in DJF see figure 2.6. This
indicates that the increasing rainfall during 20th century over Semarang city is caused by the rains that came more often, raising the probability of floods in the region.
In contrast, a downward trend appears in dry season MAM, indicating a decrease of wet days frequency from 70 to 67 days that is associated with greater chance of dry season that comes earlier
see figure 2.5 and 2.6. For the wet days frequency during JJA, the trend seems to be relatively flat at 40 days with a slight increase.
CCROM-IPB 2010 also provides threshold analysis of rainfall of Semarang City and concluded that the flooding would occur if rainfall is 302 mm or above, while drought will happen if rainfall is less
than 84 mm. Unfortunately, a future projection on rainfall and the number of wet days is not available in Semarang City. This report then assumed that the dry season will increase one month
longer than the trend and the rainy season will increase up to 2 months longer than the current trend.
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Figure 2.5: Trends of Seasonal Rainfall in Semarang City CCROM IPB, 2010: 42
Gambar 3.5.
Figure 2.6: Trends of Seasonal Wet Days Frequency in Semarang City CCROM, 2010: 43
Gambar 3.6
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2.1.3. Increase in Sea Level Rise
The elevation of Semarang seawater continued to rise from 1985 until the year 2008 Figure 2.7. Sea level rise in Semarang Coast from the year 1985-1998 is 58.2 cm, with an average annual sea level
rise at 4.47 cm year DKP, 2008. Later in the year 1998-2003 sea level decreased. But the declining in sea level that occurred from the years 1998-2003 are considered not valid due to the instrument
failure DKP, 2008. Based on water level data from year 2003-2008 it was known that sea level trend turned high again Figure 2.7. While for sea level rise in Semarang waters year 2003 -2008 is 37.2 cm,
the average sea level rise per year is 7.43 cm year DKP, 2008. In order to know the level of sea level rise due to the influence of global warming in Semarang, the
difference between the rise sea water with a total value of land subsidence on the location of tidal stations were calculated. Data of sea level elevation sea years 1985-1998 and 2003-2008 were used.
The calculation of sea level rise due to global warming by considering the reduction of land subsidence is about 5.165 cm year, so rising sea levels due to global warming is about 7.8 mmyear.
Figure 2.7: Sea Elevation in Semarang City 1985-2008
Source: Bakosurtanal Data analyzed by DKP 2008
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Meanwhile, the vulnerability assessment VA estimates that the average increase in sea level elevation will approximately at 21 cm in 2050, and 48-60 cm in 2100. Here is a table of climate
change scenarios obtained previously from the VA in Semarang City CCROM IPB, 2010.
Table 2.2: Sea Level Rise Scenario in Semarang City CCROM IPB, 2010
2000 2025
2050 2100
SRESA2: moderate 2
10 21
60 Range
0-4 4-20
9-41 15-112
SRESB1: moderate 2
10 21
48 Range
0-4 4-22
9-42 18-85
Source: CCROM-IPB 2010
Estimation made by DKP slightly more pessimistic than the estimation of CCROM-IPB, with the SLR difference about 20 cm in 100 years to come. However, DKP provides more complete spatial analysis
information about the consequences of such changes. With the estimated level rise sea water of 0.8 m for the next 100 years, the estimated sea water inundation in Semarang City will reach distances
ranging from 1.7-3.0 km to the ground, where the total inundated area will up to 8537.9 ha.
Figure 2.8 a: Sea Water Inundation in Semarang City in The Next 100 Years with SLR Estimation at 80 cm
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Figure 2.8 a shows a simulation of sea water
inundation over next 100 years in Semarang City.
The dark blue color in the eastern and western
part of city represents 20 cm inundation. The dark
blue color becomes lighter overtime. The
lightest represents 80 cm inundation. The blue
gradation in between represents 40 cm and
60 cm sea water inunda- tion
Figure 2.8 b: Sea Water Inundation in Semarang City in the Next 100 Years with SLR Estimation at 80 cm
Source: DKP 2008
2.1.4. Wind Pattern
