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Water and climate change
B.Y. LeeDirector of the Hong Kong Observatory
May 2010
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Global warming :
“Most of the observed increase in globally-
averaged temperatures since the mid-20th century
is very likely due to the observed increase in man-
made greenhouse-gas (GHG) concentrations”
(United Nations Intergovernmental Panel on Climate Change (IPCC),
Fourth Assessment Report (AR4), 2007)
Very likely = 90%
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About 10% increase relative to the 1980-1999 average of 2324 mm
About 5% or 120mm less than the 1980-1999 average
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( 相片來源:水務署 Photo from Water Supplies Department)
香港極香港極端少雨端少雨和極和極端多端多雨的年數雨的年數Number of extremely dry years and extremely wet years in Hong KongNumber of extremely dry years and extremely wet years in Hong Kong
( 相片來源:水務署 Photo from Water Supplies Department)( 相片來源:水務署 Photo from Water Supplies Department)( 相片來源:水務署 Photo from Water Supplies Department)( 相片來源:水務署 Photo from Water Supplies Department)( 相片來源:水務署 Photo from Water Supplies Department)
極端少雨的年數極端少雨的年數 Extremely dry yearsExtremely dry years
極端多雨的年數極端多雨的年數 Extremely wet yearsExtremely wet years
期間Period
1885 - 2000 2 2
21st century 4 10
( 相片來源:水務署 Photo from Water Supplies Department) ( 相片來源:渠務署 Photo from Drainage Services Department)
Notes : Extremely dry years - annual rainfall less than 1282 mm; extremely wet years - annual rainfall more than 3187 mm 極端少雨的年數 - 年雨量低於 1282 毫米 ; 極端多雨的年數 - 年雨量高於 3187 毫米
( 相片來源:渠務署 Photo from Drainage Services Department)
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Personally per capita 100 litres/day
Daily food consumption 2000-5000 litres
1 kg bolt of cloth >10 000 litres
1 kg of beef 15 000 litres
1 kg of vegetable 2000 litres
Water usage
(source : The Economist, 11 April 2009)
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What about the melting glaciers in the Himalayas?
Mean annual mass balance [Note] of reference glaciers from 1980 to 2008
with positive values in blue and negative values in red..(Source : World Glacier Monitoring Service : Preliminary
glacier mass balance data 2007/2008
http://www.geo.unizh.ch/wgms/mbb/sum08.html)
Source : World Glacier Monitoring Service : Preliminary glacier mass balancedata 2007/2008 http://www.geo.unizh.ch/wgms/mbb/sum08.html)
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Flooding of the coastal areas becomes easier
under tropical cyclone situations
Sea level rise, plus storm surge
waves caused by typhoon rise in sea level
coast coast
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Magnitude of extreme sea levels at Victoria Harbour based on past data, a projected rise of 0.59 m and of 1.4 m.
Extreme sea-levels at Victoria Harbour
Return period (year)
Extreme sea-level (mCD) based on
past data
Extreme sea-level (mCD) after a mean of sea-level rise of 0.59 m
Extreme sea-level (mCD) after a mean of sea-level rise of 1.4 m
2 2.9 3.5 4.3
5 3.1 3.7 4.5
10 3.3 3.8 4.7
20 3.4 4.0 4.8
50 3.5 4.1 4.9
Note: mCD = metres above Chart Datum.Chart Datum is 0.146 metre below Principal
Datum.
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(courtesy of TVB)
Flooding in Tai O after Typhoon Hagupit (September 2008)