Impact Assessment of Climate Change and Sea Level Rise on ...

1.3 Review <strong>of</strong> Past Studies
A number <strong>of</strong> studies on impact assessment <strong>of</strong> climate change <strong>and</strong> sea level rise had been
carried out in the past. Some <strong>of</strong> the relevant past study reports have been reviewed to find the
findings <strong>of</strong> earlier studies:
4 th IPCC, Technical Summary, 2007, “A Report <strong>of</strong> Working Group I <strong>of</strong> the
Intergovernmental Panel on <strong>Climate</strong> <strong>Change</strong>”
In the six years since the IPCC’s Third <strong>Assessment</strong> Report (TAR), significant progress has
been made in underst<strong>and</strong>ing past <strong>and</strong> recent climate change <strong>and</strong> in projecting future changes.
These advances have arisen from large amounts <strong>of</strong> new data, more sophisticated analyses <strong>of</strong>
data, improvements in the underst<strong>and</strong>ing <strong>and</strong> simulation <strong>of</strong> physical processes in climate
models <strong>and</strong> more extensive exploration <strong>of</strong> uncertainty ranges in model results.
The dominant factor in the radiative forcing <strong>of</strong> climate in the industrial era is the increasing
concentration <strong>of</strong> various greenhouse gases in the atmosphere. Several <strong>of</strong> the major
greenhouse gases occur naturally but increases in their atmospheric concentrations over the
last 250 years are due largely to human activities.
Long-Lived Green House Gases (LLGHGs), for example, CO 2 , methane (CH 4 ) <strong>and</strong> nitrous
oxide (N 2 O), are chemically stable <strong>and</strong> persist in the atmosphere over time scales <strong>of</strong> a decade
to centuries or longer, so that their emission has a long-term influence on climate.
The concentration <strong>of</strong> atmospheric CO 2 has increased from a pre-industrial value <strong>of</strong> about 280
ppm to 379 ppm in 2005. The CH 4 abundance in 2005 <strong>of</strong> about 1774 ppb is more than double
<strong>of</strong> its pre-industrial value. The N 2 O concentration in 2005 was 319 ppb, about 18% higher
than its pre-industrial value. Over the 1961 to 2003 period, the average rate <strong>of</strong> global mean
sea level rise is estimated from tide gauge data to be 1.8 ± 0.5 mm yr -1 .
Projected global average surface warming <strong>and</strong> sea level rise at the end <strong>of</strong> the year 2100 based
on AOGCMs is presented in the following table.
Scenarios
Item
B1 A1T B2 A1B A2 A1Fl
Temperature 1.1 – 2.9 1.4 – 3.8 1.4 – 3.8 1.7 – 4.4 2.0 – 5.4 2.4 – 6.4
<strong>Sea</strong> <strong>Level</strong> <strong>Rise</strong> 0.18 – 0.38 0.20 – 0.45 0.20 – 0.43 0.21 – 0.48 0.23 – 0.51 0.26 – 0.59
Projected precipitation change in Southeast Asia during the 21st century based on AOGCMs
is presented in the table below.
Sub- <strong>Sea</strong>son 2010 - 2039 2040 - 2069 2070 - 2099
regions
Scenarios
A1Fl B1 A1Fl B1 A1Fl B1
South DJF -3 4 0 0 -16 -6
Asia MAM 7 8 26 24 31 20
JJA 5 7 13 11 26 15
SON 1 3 8 6 26 10
Note 1 : A1 Scenario – based on homogeneous world <strong>of</strong> very rapid economic growth, high global population that peaks in
mid-century <strong>and</strong> the rapid introduction <strong>of</strong> new <strong>and</strong> more efficient technologies. It represents a convergent world with a
substantial reduction in regional per capita income. Based on emission it is divided into three categories such as A1Fl, A1T
<strong>and</strong> A1B. A1Fl – Based on fossil fuel intensive – represent very high emission
B1 Scenario: based on convergent world with the same global populations as in A1 but with rapid change in economic
structures <strong>and</strong> the introduction <strong>of</strong> clean <strong>and</strong> resource-efficient technologies. Special emphasis is given on global solution to
economic, social <strong>and</strong> environmental sustainability including improved equity. It represents very low emission.
Note 2 : DJF: December, January & February; MAM: March. April & May; JJA: June, July & August; SON: September,
October &November (-ve: decrease)
If radiative forcing were to be stabilised in 2100 at A1B concentrations, thermal expansion
alone would lead to 0.3 to 0.8 m <strong>of</strong> sea level rise by 2300.
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