71 Thus, this shows the summer and winters nights are becoming more warmer and clear
indication of climate change and has contributed to increase of mean T as shown in Figure 5.28. The similar pattern is also reflected with highest Tmax in summer April and lowest
Tmin in winter Dec.
5.3 Sea level rise and storm surges
The Fourth Assessment Report AR4 of the
United Nations
Intergovernmental Panel on Climate Change
IPCC
, is the fourth in a series of reports intended to assess scientific, technical and socio-economic information concerning
climate change
, its potential effects, and options for adaptation and mitigation. The report is the largest and most detailed summary of
the climate change situation ever undertaken, involving thousands of authors from dozens of countries, and states in its summary,
•
Warming of the climate system is unequivocal.
•
Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas
concentrations.
The Special Report on Emissions Scenarios SRES was a report prepared by the Intergovernmental Panel on Climate Change IPCC for the Third Assessment Report TAR
in 2001, on future emission scenarios to be used for driving global circulation models to develop climate change scenarios. It was used to replace the IS92 scenarios used for the
IPCC Second Assessment Report
of 1995. The SRES Scenarios were also used for the
Fourth Assessment Report
AR4 in 2007, and have been subject to discussion about whether emissions growth since 2000 makes these scenarios obsolete.
72
Table 5.5. SRES scenario Source: United Nations – IPCC
Current sea level rise has occurred at a mean rate of 1.8 mm per year for the past century, and more recently at rates estimated near 2.8 ± 0.4 to 3.1 ± 0.7mm per year 1993-2003. Current
sea level rise is due partly to human-induced
global warming
, which will increase sea level over the coming century and longer periods. Increasing temperatures result in sea level rise
by the
thermal expansion
of water and through the addition of water to the oceans from the melting of continental
ice sheets
. Thermal expansion, which is well-quantified, is currently the primary contributor to sea level rise and is expected to be the primary contributor over the
course of the next century. Glacial contributions to sea-level rise are less important, and are more difficult to predict and quantify. Values for predicted sea level rise over the course of
the next century typically range from 90 to 880 mm, with a central value of 480 mm. Based on an analog to the deglaciation of North America at 9,000 years before present, some
scientists predict sea level rise of 1.3 meters in the next century. However, models of glacial flow in the smaller present-day ice sheets show that a probable maximum value for sea level
rise in the next century is 80 centimeters, based on limitations on how quickly ice can flow below the
equilibrium line altitude
and to the sea.
5.3.1
Future sea level rise
In 2007, the
Intergovernmental Panel on Climate Change
s
Fourth Assessment Report
predicted that by 2100,
global warming
will lead to a sea level rise of 19 to 58 cm, depending on which of six possible world scenarios comes to pass.
These sea level rises could lead to difficulties for shore-based communities in the next centuries: for example, many major cities such as London and
New Orleans
already need storm-surge defenses, and would need more if sea level rose, though they also face issues
The four SRES
scenario families of the Fourth Assessment Report vs. projected global average surface warming until 2100
more economic focus more environmental focus
Globalisation homogeneous world
A1
rapid economic growth groups: A1T; A1B; A1Fl
1.4 - 6.4 °C B1
